/*      $NetBSD: tree.c,v 1.716 2026/07/15 05:35:09 rillig Exp $        */

/*
 * Copyright (c) 1994, 1995 Jochen Pohl
 * All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Jochen Pohl for
 *      The NetBSD Project.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
#if defined(__RCSID)
__RCSID("$NetBSD: tree.c,v 1.716 2026/07/15 05:35:09 rillig Exp $");
#endif

#include <float.h>
#include <limits.h>
#include <math.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>

#include "lint1.h"


typedef struct integer_constraints {
        int64_t         smin;   /* signed minimum */
        int64_t         smax;   /* signed maximum */
        uint64_t        umin;   /* unsigned minimum */
        uint64_t        umax;   /* unsigned maximum */
        uint64_t        bclr;   /* bits that are definitely clear */
} integer_constraints;


static int64_t
s64_min(int64_t a, int64_t b)
{
        return a < b ? a : b;
}

static int64_t
s64_max(int64_t a, int64_t b)
{
        return a > b ? a : b;
}

static uint64_t
s64_abs(int64_t x)
{
        return x >= 0 ? (uint64_t)x : -(uint64_t)x;
}

static int64_t
s64_shr(int64_t x, unsigned amount)
{
        return x >= 0
            ? (int64_t)((uint64_t)x >> amount)
            : (int64_t)~(~(uint64_t)x >> amount);
}

static uint64_t
u64_min(uint64_t a, uint64_t b)
{
        return a < b ? a : b;
}

static uint64_t
u64_max(uint64_t a, uint64_t b)
{
        return a > b ? a : b;
}

static uint64_t
u64_fill_right(uint64_t x)
{
        x |= x >> 1;
        x |= x >> 2;
        x |= x >> 4;
        x |= x >> 8;
        x |= x >> 16;
        x |= x >> 32;
        return x;
}

static unsigned
u64_width(uint64_t x)
{
        unsigned m = 0;
        if (x >> 32 != 0)
                x >>= 32, m += 32;
        if (x >> 16 != 0)
                x >>= 16, m += 16;
        if (x >> 8 != 0)
                x >>= 8, m += 8;
        if (x >> 4 != 0)
                x >>= 4, m += 4;
        if (x >> 2 != 0)
                x >>= 2, m += 2;
        if (x >> 1 != 0)
                x >>= 1, m++;
        if (x > 0)
                m++;
        return m;
}

static int
portable_rank_cmp(tspec_t t1, tspec_t t2)
{
        const ttab_t *p1 = type_properties(t1), *p2 = type_properties(t2);
        lint_assert(p1->tt_rank_kind == p2->tt_rank_kind);
        lint_assert(p1->tt_rank_value > 0);
        lint_assert(p2->tt_rank_value > 0);
        return (int)p1->tt_rank_value - (int)p2->tt_rank_value;
}

static unsigned
width_in_bits(const type_t *tp)
{
        lint_assert(is_integer(tp->t_tspec));
        return tp->t_bitfield
               ? tp->t_bit_field_width
               : size_in_bits(tp->t_tspec);
}

static uint64_t
ui_max_value(const type_t *tp)
{
        return value_bits(width_in_bits(tp));
}

static int64_t
si_max_value(const type_t *tp)
{
        return (int64_t)(ui_max_value(tp) >> 1);
}

static int64_t
si_min_value(const type_t *tp)
{
        return -si_max_value(tp) - 1;
}

static int64_t
si_mult_sat(const type_t *tp, int64_t l, int64_t r)
{
        uint64_t al = s64_abs(l);
        uint64_t ar = s64_abs(r);
        bool neg = (l >= 0) != (r >= 0);
        int64_t max = si_max_value(tp);
        uint64_t max_prod = (uint64_t)max + (neg ? 1 : 0);
        if (al == 0 || ar <= max_prod / al)
                return l * r;
        else if (neg)
                return -1 - max;
        else
                return max;
}

static int64_t
si_plus_sat(const type_t *tp, int64_t a, int64_t b)
{
        if (b >= 0) {
                int64_t max = si_max_value(tp);
                return a <= max - b ? a + b : max;
        } else {
                int64_t min = si_min_value(tp);
                return a >= min - b ? a + b : min;
        }
}

static int64_t
si_minus_sat(const type_t *tp, int64_t a, int64_t b)
{
        if (b >= 0) {
                int64_t min = si_min_value(tp);
                return a >= min + b ? a - b : min;
        } else {
                int64_t max = si_max_value(tp);
                return a <= max + b ? a - b : max;
        }
}

static bool
ic_maybe_signed(const type_t *tp, integer_constraints ic)
{
        return !is_uinteger(tp->t_tspec) && ic.bclr >> 63 == 0;
}

static bool
ic_maybe_signed_binary(const type_t *tp,
    integer_constraints a, integer_constraints b)
{
        return !is_uinteger(tp->t_tspec) && (a.bclr & b.bclr) >> 63 == 0;
}

static integer_constraints
ic_any(const type_t *tp)
{
        integer_constraints c;

        unsigned width = width_in_bits(tp);
        uint64_t vbits = value_bits(width);
        if (is_uinteger(tp->t_tspec)) {
                c.smin = width < 64 ? 0 : INT64_MIN;
                c.smax = width < 64 ? (int64_t)vbits : INT64_MAX;
                c.umin = 0;
                c.umax = vbits;
                c.bclr = ~c.umax;
        } else {
                c.smin = -1 - (int64_t)(vbits >> 1);
                c.smax = (int64_t)(vbits >> 1);
                c.umin = 0;
                c.umax = UINT64_MAX;
                c.bclr = 0;
        }
        return c;
}

static integer_constraints
ic_mult(const type_t *tp, integer_constraints a, integer_constraints b)
{
        integer_constraints c;

        if (ic_maybe_signed_binary(tp, a, b)) {
                int64_t ll = si_mult_sat(tp, a.smin, b.smin);
                int64_t lu = si_mult_sat(tp, a.smin, b.smax);
                int64_t ul = si_mult_sat(tp, a.smax, b.smin);
                int64_t uu = si_mult_sat(tp, a.smax, b.smax);

                c.smin = s64_min(ll, s64_min(lu, s64_min(ul, uu)));
                c.smax = s64_max(ll, s64_max(lu, s64_max(ul, uu)));
                c.umin = c.smin >= 0 ? (uint64_t)c.smin : 0;
                c.umax = c.smin >= 0 ? (uint64_t)c.smax : UINT64_MAX;
                c.bclr = ~u64_fill_right(c.umax);
                return c;
        }

        if (a.umax > 0 && b.umax > ic_any(tp).umax / a.umax)
                return ic_any(tp);

        c.smin = INT64_MIN;
        c.smax = INT64_MAX;
        c.umin = a.umin * b.umin;
        c.umax = a.umax * b.umax;
        c.bclr = ~u64_fill_right(c.umax);
        return c;
}

static integer_constraints
ic_div(const type_t *tp, integer_constraints a, integer_constraints b)
{
        if (ic_maybe_signed_binary(tp, a, b)) {
                if (b.smin >= 0)
                        return a;
                return ic_any(tp);
        }

        integer_constraints c;
        c.smin = INT64_MIN;
        c.smax = INT64_MAX;
        c.umin = a.umin / u64_max(b.umax, 1);
        c.umax = a.umax / u64_max(b.umin, 1);
        c.bclr = ~u64_fill_right(c.umax);
        return c;
}

static integer_constraints
ic_mod(const type_t *tp, integer_constraints a, integer_constraints b)
{
        if (ic_maybe_signed_binary(tp, a, b)) {
                uint64_t max_abs_b = u64_max(s64_abs(b.smin), s64_abs(b.smax));
                if (max_abs_b >> 63 != 0 || max_abs_b == 0)
                        return a;

                integer_constraints c;
                c.smin = s64_max(a.smin, -(int64_t)(max_abs_b - 1));
                c.smax = s64_min(a.smax, (int64_t)(max_abs_b - 1));
                c.umin = 0;
                c.umax = UINT64_MAX;
                c.bclr = 0;
                return c;
        }

        integer_constraints c;
        c.smin = INT64_MIN;
        c.smax = INT64_MAX;
        c.umin = 0;
        c.umax = b.umax - 1;
        c.bclr = ~u64_fill_right(c.umax);
        return c;
}

static integer_constraints
ic_plus(const type_t *tp, integer_constraints a, integer_constraints b)
{
        if (ic_maybe_signed_binary(tp, a, b)) {
                integer_constraints c;
                c.smin = si_plus_sat(tp, a.smin, b.smin);
                c.smax = si_plus_sat(tp, a.smax, b.smax);
                c.umin = c.smin >= 0 ? (uint64_t)c.smin : 0;
                c.umax = c.smin >= 0 ? (uint64_t)c.smax : UINT64_MAX;
                c.bclr = 0;
                return c;
        }

        uint64_t max = ui_max_value(tp);
        integer_constraints c;
        c.smin = INT64_MIN;
        c.smax = INT64_MAX;
        if (b.umax <= max - a.umax) {
                c.umin = a.umin + b.umin;
                c.umax = a.umax + b.umax;
        } else {
                c.umin = 0;
                c.umax = max;
        }
        if (c.umax >> 63 == 0) {
                c.smin = 0;
                c.smax = (int64_t)c.umax;
        }
        c.bclr = ~u64_fill_right(c.umax);
        return c;
}

static integer_constraints
ic_minus(const type_t *tp, integer_constraints a, integer_constraints b)
{
        integer_constraints c;
        c.smin = si_minus_sat(tp, a.smin, b.smax);
        c.smax = si_minus_sat(tp, a.smax, b.smin);

        if (ic_maybe_signed_binary(tp, a, b)) {
                c.umin = c.smin >= 0 ? (uint64_t)c.smin : 0;
                c.umax = c.smin >= 0 ? (uint64_t)c.smax : UINT64_MAX;
        } else if (a.umin >= b.umax) {
                c.umin = a.umin - b.umax;
                c.umax = a.umax - b.umin;
        } else {
                c.umin = 0;
                c.umax = is_uinteger(tp->t_tspec) ? ui_max_value(tp)
                    : UINT64_MAX;
        }
        c.bclr = ~u64_fill_right(c.umax);
        return c;
}

static integer_constraints
ic_shl(const type_t *tp, integer_constraints a, integer_constraints b)
{
        if (ic_maybe_signed(tp, a))
                return ic_any(tp);

        unsigned amount;
        if (b.smin == b.smax && b.smin >= 0 && b.smin < 64)
                amount = (unsigned)b.smin;
        else if (b.umin == b.umax && b.umin < 64)
                amount = (unsigned)b.umin;
        else
                return ic_any(tp);

        integer_constraints c;
        c.umin = a.umin << amount;
        c.umax = a.umax << amount;
        if (c.umax >> (width_in_bits(tp) - 1) == 0) {
                c.smin = (int64_t)c.umin;
                c.smax = (int64_t)c.umax;
        } else {
                c.smin = INT64_MIN;
                c.smax = INT64_MAX;
        }
        c.bclr = a.bclr << amount | (((uint64_t)1 << amount) - 1);
        return c;
}

static integer_constraints
ic_shr(const type_t *tp, integer_constraints a, integer_constraints b)
{
        if (ic_maybe_signed(tp, a))
                return ic_any(tp);

        unsigned amount;
        if (b.smin == b.smax && b.smin >= 0 && b.smin < 64)
                amount = (unsigned)b.smin;
        else if (b.umin == b.umax && b.umin < 64)
                amount = (unsigned)b.umin;
        else
                return ic_any(tp);

        integer_constraints c;
        c.smin = s64_shr(a.smin, amount);
        c.smax = s64_shr(a.smax, amount);
        c.umin = a.umin >> amount;
        c.umax = a.umax >> amount;
        c.bclr = a.bclr >> amount | ~(~(uint64_t)0 >> amount);
        return c;
}

static integer_constraints
ic_bitand(integer_constraints a, integer_constraints b)
{
        integer_constraints c;
        c.smin = a.smin & b.smin;
        c.smax = a.smax & b.smax;
        c.umin = a.umin & b.umin;
        c.umax = a.umax & b.umax;
        c.bclr = a.bclr | b.bclr;
        return c;
}

static integer_constraints
ic_bitxor(const type_t *tp, integer_constraints a, integer_constraints b)
{
        if (ic_maybe_signed_binary(tp, a, b))
                return ic_any(tp);

        integer_constraints c;
        c.smin = a.smin & b.smin;
        c.smax = a.smax | b.smax;
        c.umin = a.umin & b.umin;
        c.umax = a.umax | b.umax;
        c.bclr = a.bclr & b.bclr;
        return c;
}

static integer_constraints
ic_bitor(integer_constraints a, integer_constraints b)
{
        integer_constraints c;
        c.smin = a.smin | b.smin;
        c.smax = a.smax | b.smax;
        c.umin = a.umin | b.umin;
        c.umax = a.umax | b.umax;
        c.bclr = a.bclr & b.bclr;
        return c;
}

static integer_constraints
ic_quest_colon(integer_constraints a, integer_constraints b)
{
        integer_constraints c;
        c.smin = s64_min(a.smin, b.smin);
        c.smax = s64_max(a.smax, b.smax);
        c.umin = u64_min(a.umin, b.umin);
        c.umax = u64_max(a.umax, b.umax);
        c.bclr = a.bclr & b.bclr;
        return c;
}

static integer_constraints
ic_con(const type_t *tp, const val_t *v)
{
        lint_assert(is_integer(tp->t_tspec));
        int64_t si = v->u.integer;
        uint64_t ui = (uint64_t)si;

        integer_constraints c;
        c.smin = si;
        c.smax = si;
        c.umin = ui;
        c.umax = ui;
        c.bclr = ~ui;
        return c;
}

static integer_constraints
ic_cvt(const type_t *ntp, const type_t *otp, integer_constraints a)
{
        unsigned new_width = width_in_bits(ntp);
        unsigned old_width = width_in_bits(otp);
        bool new_unsigned = is_uinteger(ntp->t_tspec);
        bool old_unsigned = is_uinteger(otp->t_tspec);

        if (new_width >= old_width && new_unsigned == old_unsigned)
                return a;
        if (new_width > old_width && old_unsigned)
                return a;
        if (new_unsigned && (~value_bits(new_width) & ~a.bclr) == 0)
                return a;
        return ic_any(ntp);
}

static integer_constraints
ic_unsigned_range(uint64_t minimum, uint64_t maximum)
{
        integer_constraints c;
        lint_assert(minimum <= maximum);
        c.smin = maximum <= INT64_MAX ? (int64_t)minimum : INT64_MIN;
        c.smax = maximum <= INT64_MAX ? (int64_t)maximum : INT64_MAX;
        c.umin = minimum;
        c.umax = maximum;
        c.bclr = ~c.umax;
        return c;
}

static integer_constraints
ic_signed_range(int64_t minimum, int64_t maximum)
{
        integer_constraints c;
        lint_assert(minimum <= maximum);
        c.smin = minimum;
        c.smax = maximum;
        c.umin = minimum >= 0 ? (uint64_t)minimum : 0;
        c.umax = minimum >= 0 ? (uint64_t)maximum : UINT64_MAX;
        c.bclr = ~c.umax;
        return c;
}

static integer_constraints
ic_call(const function_call *call)
{
        if (!(call->func->tn_op == ADDR
            && call->func->u.ops.left->tn_op == NAME))
                goto any;

        const char *name = call->func->u.ops.left->u.sym->s_name;

        if (strcmp(name, "strlen") == 0
            || strcmp(name, "strcspn") == 0
            || strcmp(name, "strspn") == 0
            || strcmp(name, "strlcpy") == 0
            || strcmp(name, "strlcat") == 0)
                return ic_unsigned_range(0, INT_MAX - 1);
        if ((strcmp(name, "read") == 0 || strcmp(name, "write") == 0)
            && call->args_len == 3
            && call->args[2]->tn_op == CON
            && is_uinteger(call->args[2]->tn_type->t_tspec)
            && call->args[2]->u.value.u.integer >= 0)
                return ic_signed_range(-1, call->args[2]->u.value.u.integer);

        // https://gcc.gnu.org/onlinedocs/gcc/Bit-Operation-Builtins.html
        if (strcmp(name, "__builtin_clz") == 0
            || strcmp(name, "__builtin_ctz") == 0
            || strcmp(name, "__builtin_clrsb") == 0)
                return ic_unsigned_range(0, INT_SIZE - 1);
        if (strcmp(name, "__builtin_ffs") == 0
            || strcmp(name, "__builtin_popcount") == 0)
                return ic_unsigned_range(0, INT_SIZE);
        if (strcmp(name, "__builtin_clzl") == 0
            || strcmp(name, "__builtin_ctzl") == 0
            || strcmp(name, "__builtin_clrsbl") == 0)
                return ic_unsigned_range(0, LONG_SIZE - 1);
        if (strcmp(name, "__builtin_ffsl") == 0
            || strcmp(name, "__builtin_popcountl") == 0)
                return ic_unsigned_range(0, LONG_SIZE);
        if (strcmp(name, "__builtin_clzll") == 0
            || strcmp(name, "__builtin_ctzll") == 0
            || strcmp(name, "__builtin_clrsbll") == 0)
                return ic_unsigned_range(0, LLONG_SIZE - 1);
        if (strcmp(name, "__builtin_ffsll") == 0
            || strcmp(name, "__builtin_popcountll") == 0)
                return ic_unsigned_range(0, LLONG_SIZE);
        if ((strcmp(name, "__builtin_clzg") == 0
            || strcmp(name, "__builtin_ctzg") == 0
            || strcmp(name, "__builtin_clrsbg") == 0)
            && call->args_len == 1
            && is_integer(call->args[0]->tn_type->t_tspec))
                return ic_unsigned_range(0,
                    width_in_bits(call->args[0]->tn_type) - 1);
        if ((strcmp(name, "__builtin_ffsg") == 0
            || strcmp(name, "__builtin_popcountg") == 0)
            && call->args_len == 1
            && is_integer(call->args[0]->tn_type->t_tspec))
                return ic_unsigned_range(0,
                    width_in_bits(call->args[0]->tn_type));
        if (strcmp(name, "__builtin_parity") == 0
            || strcmp(name, "__builtin_parityl") == 0
            || strcmp(name, "__builtin_parityll") == 0
            || strcmp(name, "__builtin_parityg") == 0)
                return ic_unsigned_range(0, 1);

any:
        return ic_any(call->func->tn_type->t_subt->t_subt);
}

static integer_constraints
ic_expr(const tnode_t *tn)
{
        integer_constraints lc, rc;

        lint_assert(is_integer(tn->tn_type->t_tspec));

        switch (tn->tn_op) {
        case MULT:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_mult(tn->tn_type, lc, rc);
        case DIV:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_div(tn->tn_type, lc, rc);
        case MOD:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_mod(tn->tn_type, lc, rc);
        case PLUS:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_plus(tn->tn_type, lc, rc);
        case MINUS:
                if (tn->u.ops.left->tn_type->t_tspec == PTR)
                        return ic_any(tn->tn_type);
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_minus(tn->tn_type, lc, rc);
        case SHL:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_shl(tn->tn_type, lc, rc);
        case SHR:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_shr(tn->tn_type, lc, rc);
        case BITAND:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_bitand(lc, rc);
        case BITXOR:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_bitxor(tn->tn_type, lc, rc);
        case BITOR:
                lc = ic_expr(tn->u.ops.left);
                rc = ic_expr(tn->u.ops.right);
                return ic_bitor(lc, rc);
        case QUEST:
                lc = ic_expr(tn->u.ops.right->u.ops.left);
                rc = ic_expr(tn->u.ops.right->u.ops.right);
                return ic_quest_colon(lc, rc);
        case CON:
                return ic_con(tn->tn_type, &tn->u.value);
        case CVT:
                if (!is_integer(tn->u.ops.left->tn_type->t_tspec))
                        return ic_any(tn->tn_type);
                lc = ic_expr(tn->u.ops.left);
                return ic_cvt(tn->tn_type, tn->u.ops.left->tn_type, lc);
        case CALL:
                return ic_call(tn->u.call);
        default:
                return ic_any(tn->tn_type);
        }
}

uint64_t
possible_bits(const tnode_t *tn)
{
        return ~ic_expr(tn).bclr;
}


static struct {
        size_t len;
        size_t cap;
        evaluation_mode *items;
} evaluation_modes;

/* Push the minimum of the given mode and the already active mode. */
void
push_evaluation_mode(evaluation_mode m)
{
        if (evaluation_modes.len >= evaluation_modes.cap) {
                evaluation_modes.cap = 2 * evaluation_modes.cap + 16;
                evaluation_modes.items = xrealloc(
                    evaluation_modes.items,
                    evaluation_modes.cap * sizeof(*evaluation_modes.items));
        }

        evaluation_mode top = evaluation_modes.len > 0
            ? evaluation_modes.items[evaluation_modes.len - 1]
            : EM_EVAL;
        evaluation_modes.items[evaluation_modes.len++] =
            (int)top < (int)m ? top : m;
}

void
pop_evaluation_mode(void)
{
        evaluation_modes.len--;
}

bool
is_evaluation_mode(evaluation_mode m)
{
        evaluation_mode top = evaluation_modes.len > 0
            ? evaluation_modes.items[evaluation_modes.len - 1]
            : EM_EVAL;
        return (int)top >= (int)m;
}


bool
attributes_contain(const attribute_list *attrs, const char *str)
{
        for (size_t i = 0, n = attrs->len; i < n; i++) {
                const attribute *attr = attrs->attrs + i;
                if (attr->prefix == NULL && strcmp(attr->name, str) == 0)
                        return true;
        }
        return false;
}

/* Build 'pointer to tp', 'array of tp' or 'function returning tp'. */
type_t *
block_derive_type(type_t *tp, tspec_t t)
{

        type_t *tp2 = block_zero_alloc(sizeof(*tp2), "type");
        tp2->t_tspec = t;
        tp2->t_subt = tp;
        return tp2;
}

/*
 * Derive 'pointer to tp'.
 * The memory is freed at the end of the current expression.
 */
static type_t *
expr_derive_ptr_type(type_t *tp)
{

        type_t *tp2 = expr_zero_alloc(sizeof(*tp2), "type");
        tp2->t_tspec = PTR;
        tp2->t_subt = tp;
        return tp2;
}

static const char *
function_call_descr(const function_call *call)
{
        if ((call->func->tn_op == ADDR || call->func->tn_op == LOAD)
            && call->func->u.ops.left->tn_op == NAME)
                return call->func->u.ops.left->u.sym->s_name;
        return type_name(call->func->tn_type->t_subt);
}

static size_t
str_len(const tnode_t *tn)
{
        const buffer *buf = tn->u.str_literals;
        if (tn->tn_type->t_subt->t_tspec != CHAR)
                return buf->len;
        quoted_iterator it = { .end = 0 };
        size_t len = 0;
        while (quoted_next(buf, &it))
                len++;
        return len;
}

/* Create an expression from a unary or binary operator and its operands. */
static tnode_t *
build_op(op_t op, bool sys, type_t *type, tnode_t *ln, tnode_t *rn)
{

        tnode_t *ntn = expr_alloc_tnode();
        ntn->tn_op = op;
        ntn->tn_type = type;
        ntn->tn_sys = sys;
        ntn->u.ops.left = ln;
        ntn->u.ops.right = rn;

        if (op == INDIR || op == FSEL) {
                lint_assert(ln->tn_type->t_tspec == PTR);
                tspec_t t = ln->tn_type->t_subt->t_tspec;
                ntn->tn_lvalue = t != FUNC && t != VOID;
        }

        return ntn;
}

tnode_t *
build_constant(type_t *tp, val_t *v)
{

        tnode_t *n = expr_alloc_tnode();
        n->tn_op = CON;
        n->tn_type = tp;
        n->u.value = *v;
        n->u.value.v_tspec = tp->t_tspec;
        free(v);
        return n;
}

static tnode_t *
build_integer_constant(tspec_t t, int64_t si)
{

        tnode_t *n = expr_alloc_tnode();
        n->tn_op = CON;
        n->tn_type = gettyp(t);
        n->u.value.v_tspec = t;
        n->u.value.v_unsigned_since_c90 = false;
        n->u.value.v_char_constant = false;
        n->u.value.u.integer = si;
        return n;
}

static void
fallback_symbol(sym_t *sym)
{

        if (Tflag && fallback_symbol_strict_bool(sym))
                return;

        if (funcsym != NULL && (strcmp(sym->s_name, "__FUNCTION__") == 0 ||
                           strcmp(sym->s_name, "__PRETTY_FUNCTION__") == 0)) {
                /* __FUNCTION__/__PRETTY_FUNCTION__ is a GCC extension */
                gnuism(316);
                goto return_function_name;
        }

        if (funcsym != NULL && strcmp(sym->s_name, "__func__") == 0) {
                if (!allow_c99)
                        /* __func__ is a C99 feature */
                        warning(317);
                /* C11 6.4.2.2 */
        return_function_name:
                sym->s_type = block_derive_type(gettyp(CHAR), ARRAY);
                sym->s_type->t_const = true;
                sym->s_type->u.dimension = (int)strlen(funcsym->s_name) + 1;
                return;
        }

        /* '%s' undefined */
        error(99, sym->s_name);
}

/*
 * Functions that are predeclared by GCC or other compilers can be called
 * with arbitrary arguments.  Since lint usually runs after a successful
 * compilation, it's the compiler's job to catch any errors.
 */
bool
is_compiler_builtin(const char *name)
{
        /* https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html */
        if (allow_gcc) {
                if (strncmp(name, "__atomic_", 9) == 0 ||
                    strncmp(name, "__builtin_", 10) == 0 ||
                    strcmp(name, "alloca") == 0 ||
                    /* obsolete but still in use, as of 2021 */
                    strncmp(name, "__sync_", 7) == 0)
                        return true;
        }

        /* https://software.intel.com/sites/landingpage/IntrinsicsGuide/ */
        if (strncmp(name, "_mm_", 4) == 0)
                return true;

        // https://clang.llvm.org/docs/LanguageExtensions.html#c11-atomic-builtins
        if (strcmp(name, "__c11_atomic_init") == 0 ||
            strcmp(name, "__c11_atomic_thread_fence") == 0 ||
            strcmp(name, "__c11_atomic_signal_fence") == 0 ||
            strcmp(name, "__c11_atomic_is_lock_free ") == 0 ||
            strcmp(name, "__c11_atomic_store") == 0 ||
            strcmp(name, "__c11_atomic_load") == 0 ||
            strcmp(name, "__c11_atomic_exchange") == 0 ||
            strcmp(name, "__c11_atomic_compare_exchange_strong") == 0 ||
            strcmp(name, "__c11_atomic_compare_exchange_weak") == 0 ||
            strcmp(name, "__c11_atomic_fetch_add") == 0 ||
            strcmp(name, "__c11_atomic_fetch_sub") == 0 ||
            strcmp(name, "__c11_atomic_fetch_and") == 0 ||
            strcmp(name, "__c11_atomic_fetch_or") == 0 ||
            strcmp(name, "__c11_atomic_fetch_xor") == 0 ||
            strcmp(name, "__c11_atomic_fetch_nand ") == 0 ||
            strcmp(name, "__c11_atomic_fetch_max") == 0 ||
            strcmp(name, "__c11_atomic_fetch_min") == 0)
                return true;

        return false;
}

static bool
str_ends_with(const char *haystack, const char *needle)
{
        size_t hlen = strlen(haystack);
        size_t nlen = strlen(needle);

        return nlen <= hlen &&
               memcmp(haystack + hlen - nlen, needle, nlen) == 0;
}

/* https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html */
static bool
is_gcc_bool_builtin(const char *name)
{
        return strncmp(name, "__builtin_", 10) == 0 &&
            (str_ends_with(name, "_overflow") ||
                str_ends_with(name, "_overflow_p"));
}

static void
build_name_call(sym_t *sym)
{

        if (is_compiler_builtin(sym->s_name)) {
                /*
                 * Do not warn about these, just assume that they are regular
                 * functions compatible with non-prototype calling conventions.
                 */
                if (allow_gcc && is_gcc_bool_builtin(sym->s_name))
                        sym->s_type = gettyp(BOOL);
        } else if (allow_c99)
                /* function '%s' implicitly declared to return int */
                error(215, sym->s_name);
        else if (!allow_trad)
                /* function '%s' implicitly declared to return int */
                warning(215, sym->s_name);

        /* XXX if !allow_c90, the symbol should be exported to level 0 */
        sym->s_type = block_derive_type(sym->s_type, FUNC);
}

/* Create a node for a name (symbol table entry). */
tnode_t *
build_name(sym_t *sym, bool is_funcname)
{

        if (sym->s_scl == NO_SCL && !in_gcc_attribute) {
                sym->s_scl = EXTERN;
                sym->s_def = DECL;
                if (is_funcname)
                        build_name_call(sym);
                else
                        fallback_symbol(sym);
        }

        lint_assert(sym->s_kind == SK_VCFT || sym->s_kind == SK_MEMBER);

        tnode_t *n = expr_alloc_tnode();
        n->tn_type = sym->s_type;
        if (sym->s_scl == BOOL_CONST) {
                n->tn_op = CON;
                n->u.value.v_tspec = BOOL;
                n->u.value.v_unsigned_since_c90 = false;
                n->u.value.v_char_constant = false;
                n->u.value.u.integer = sym->u.s_bool_constant ? 1 : 0;
        } else if (sym->s_scl == ENUM_CONST) {
                n->tn_op = CON;
                n->u.value.v_tspec = INT;       /* ENUM is in n->tn_type */
                n->u.value.v_unsigned_since_c90 = false;
                n->u.value.v_char_constant = false;
                n->u.value.u.integer = sym->u.s_enum_constant;
        } else {
                n->tn_op = NAME;
                n->u.sym = sym;
                if (sym->s_kind == SK_VCFT && sym->s_type->t_tspec != FUNC)
                        n->tn_lvalue = true;
        }

        return n;
}

tnode_t *
build_string(buffer *lit)
{
        size_t value_len = lit->len;
        if (lit->data != NULL) {
                quoted_iterator it = { .end = 0 };
                for (value_len = 0; quoted_next(lit, &it); value_len++)
                        continue;
        }

        type_t *tp = expr_zero_alloc(sizeof(*tp), "type");
        tp->t_tspec = ARRAY;
        tp->t_subt = gettyp(lit->data != NULL ? CHAR : WCHAR_TSPEC);
        tp->u.dimension = (int)(value_len + 1);

        tnode_t *n = expr_alloc_tnode();
        n->tn_op = STRING;
        n->tn_type = tp;
        n->tn_lvalue = true;

        n->u.str_literals = expr_zero_alloc(sizeof(*n->u.str_literals), "tnode.string");
        n->u.str_literals->len = lit->len;

        if (lit->data != NULL) {
                n->u.str_literals->data = expr_zero_alloc(lit->len + 1,
                    "tnode.string.data");
                (void)memcpy(n->u.str_literals->data, lit->data, lit->len + 1);
                free(lit->data);
        }
        free(lit);

        return n;
}

static bool
is_out_of_char_range(const tnode_t *tn)
{
        return tn->tn_op == CON &&
            !tn->u.value.v_char_constant &&
            !(0 <= tn->u.value.u.integer &&
                tn->u.value.u.integer < 1 << (CHAR_SIZE - 1));
}

static bool
check_nonportable_char_comparison(op_t op,
                                  const tnode_t *ln, tspec_t lt,
                                  const tnode_t *rn, tspec_t rt)
{
        if (!(hflag || pflag))
                return true;

        if (lt == CHAR && is_out_of_char_range(rn)) {
                char buf[128];
                (void)snprintf(buf, sizeof(buf), "%s %d",
                    op_name(op), (int)rn->u.value.u.integer);
                /* nonportable character comparison '%s' */
                warning(230, buf);
                return false;
        }
        if (rt == CHAR && is_out_of_char_range(ln)) {
                char buf[128];
                (void)snprintf(buf, sizeof(buf), "%d %s ?",
                    (int)ln->u.value.u.integer, op_name(op));
                /* nonportable character comparison '%s' */
                warning(230, buf);
                return false;
        }
        return true;
}

static void
check_integer_comparison(op_t op, tnode_t *ln, tnode_t *rn)
{

        tspec_t lt = ln->tn_type->t_tspec;
        tspec_t rt = rn->tn_type->t_tspec;

        if (ln->tn_op != CON && rn->tn_op != CON)
                return;

        if (!is_integer(lt) || !is_integer(rt))
                return;

        if (any_query_enabled && !in_system_header) {
                if (lt == CHAR && rn->tn_op == CON &&
                    !rn->u.value.v_char_constant) {
                        /* comparison '%s' of 'char' with plain integer %d */
                        query_message(14,
                            op_name(op), (int)rn->u.value.u.integer);
                }
                if (rt == CHAR && ln->tn_op == CON &&
                    !ln->u.value.v_char_constant) {
                        /* comparison '%s' of 'char' with plain integer %d */
                        query_message(14,
                            op_name(op), (int)ln->u.value.u.integer);
                }
        }

        if (!check_nonportable_char_comparison(op, ln, lt, rn, rt))
                return;

        if (is_uinteger(lt) && !is_uinteger(rt) &&
            rn->tn_op == CON && rn->u.value.u.integer <= 0) {
                if (rn->u.value.u.integer < 0) {
                        /* operator '%s' compares '%s' with '%s' */
                        warning(162, op_name(op),
                            expr_type_name(ln), "negative constant");
                } else if (op == LT || op == GE)
                        /* operator '%s' compares '%s' with '%s' */
                        warning(162, op_name(op), expr_type_name(ln), "0");
                return;
        }
        if (is_uinteger(rt) && !is_uinteger(lt) &&
            ln->tn_op == CON && ln->u.value.u.integer <= 0) {
                if (ln->u.value.u.integer < 0) {
                        /* operator '%s' compares '%s' with '%s' */
                        warning(162, op_name(op),
                            "negative constant", expr_type_name(rn));
                } else if (op == GT || op == LE)
                        /* operator '%s' compares '%s' with '%s' */
                        warning(162, op_name(op), "0", expr_type_name(rn));
                return;
        }
}

static const tspec_t arith_rank[] = {
        LDOUBLE, DOUBLE, FLOAT,
        UINT128, INT128,
        ULLONG, LLONG,
        ULONG, LONG,
        UINT, INT,
};

/* Keep unsigned in traditional C */
static tspec_t
usual_arithmetic_conversion_trad(tspec_t lt, tspec_t rt)
{

        size_t i;
        for (i = 0; arith_rank[i] != INT; i++)
                if (lt == arith_rank[i] || rt == arith_rank[i])
                        break;

        tspec_t t = arith_rank[i];
        if (is_uinteger(lt) || is_uinteger(rt))
                if (is_integer(t) && !is_uinteger(t))
                        return unsigned_type(t);
        return t;
}

static tspec_t
usual_arithmetic_conversion_c90(tspec_t lt, tspec_t rt)
{

        if (lt == rt)
                return lt;

        if (lt == LCOMPLEX || rt == LCOMPLEX)
                return LCOMPLEX;
        if (lt == DCOMPLEX || rt == DCOMPLEX)
                return DCOMPLEX;
        if (lt == FCOMPLEX || rt == FCOMPLEX)
                return FCOMPLEX;
        if (lt == LDOUBLE || rt == LDOUBLE)
                return LDOUBLE;
        if (lt == DOUBLE || rt == DOUBLE)
                return DOUBLE;
        if (lt == FLOAT || rt == FLOAT)
                return FLOAT;

        if (size_in_bits(lt) > size_in_bits(rt))
                return lt;
        if (size_in_bits(lt) < size_in_bits(rt))
                return rt;

        size_t i;
        for (i = 3; arith_rank[i] != INT; i++)
                if (arith_rank[i] == lt || arith_rank[i] == rt)
                        break;
        if ((is_uinteger(lt) || is_uinteger(rt)) &&
            !is_uinteger(arith_rank[i]))
                i--;
        return arith_rank[i];
}

static tnode_t *
apply_usual_arithmetic_conversions(op_t op, tnode_t *tn, tspec_t t)
{
        type_t *ntp = expr_dup_type(tn->tn_type);
        ntp->t_tspec = t;
        if (tn->tn_op != CON) {
                /* usual arithmetic conversion for '%s' from '%s' to '%s' */
                query_message(4, op_name(op),
                    expr_type_name(tn), type_name(ntp));
        }
        return convert(op, 0, ntp, tn);
}

/*
 * Apply the "usual arithmetic conversions" (C99 6.3.1.8), which gives both
 * operands the same type.
 */
static void
balance(op_t op, tnode_t **lnp, tnode_t **rnp)
{

        tspec_t lt = (*lnp)->tn_type->t_tspec;
        tspec_t rt = (*rnp)->tn_type->t_tspec;
        if (!is_arithmetic(lt) || !is_arithmetic(rt))
                return;

        tspec_t t = allow_c90
            ? usual_arithmetic_conversion_c90(lt, rt)
            : usual_arithmetic_conversion_trad(lt, rt);

        if (modtab[op].m_comparison
            && is_integer(lt) && (*lnp)->tn_op != CON
            && is_floating(t) && (*rnp)->tn_op == CON)
                /* comparing integer '%s' to floating point constant %Lg */
                warning(379, expr_type_name(*lnp),
                    (*rnp)->u.value.u.floating);

        if (t != lt)
                *lnp = apply_usual_arithmetic_conversions(op, *lnp, t);
        if (t != rt)
                *rnp = apply_usual_arithmetic_conversions(op, *rnp, t);

        if (is_integer(t)) {
                unsigned lw = width_in_bits((*lnp)->tn_type);
                unsigned rw = width_in_bits((*rnp)->tn_type);
                if (lw < rw)
                        *lnp = convert(NOOP, 0, (*rnp)->tn_type, *lnp);
                if (rw < lw)
                        *rnp = convert(NOOP, 0, (*lnp)->tn_type, *rnp);
        }
}

static tnode_t *
build_address(bool sys, tnode_t *tn)
{
        /* eliminate '&*' */
        if (tn->tn_op == INDIR &&
            tn->u.ops.left->tn_type->t_tspec == PTR &&
            tn->u.ops.left->tn_type->t_subt == tn->tn_type) {
                return tn->u.ops.left;
        }

        return build_op(ADDR, sys, expr_derive_ptr_type(tn->tn_type),
            tn, NULL);
}

static uint64_t
fold_unsigned_integer(op_t op, uint64_t l, uint64_t r,
                      uint64_t max_value, bool *overflow)
{
        switch (op) {
        case COMPL:
                return ~l & max_value;
        case UPLUS:
                return +l;
        case UMINUS:
                return -l & max_value;
        case MULT:
                *overflow = r > 0 && l > max_value / r;
                return l * r;
        case DIV:
                if (r == 0) {
                        if (is_evaluation_mode(EM_EVAL))
                                /* division by 0 */
                                error(139);
                        return max_value;
                }
                return l / r;
        case MOD:
                if (r == 0) {
                        if (is_evaluation_mode(EM_EVAL))
                                /* modulus by 0 */
                                error(140);
                        return 0;
                }
                return l % r;
        case PLUS:
                *overflow = l > max_value - r;
                return l + r;
        case MINUS:
                *overflow = l < r;
                return l - r;
        case SHL:
                /* TODO: warn about out-of-bounds 'r'. */
                /* TODO: warn about overflow. */
                return l << (r & 63);
        case SHR:
                /* TODO: warn about out-of-bounds 'r'. */
                return l >> (r & 63);
        case LT:
                return l < r ? 1 : 0;
        case LE:
                return l <= r ? 1 : 0;
        case GT:
                return l > r ? 1 : 0;
        case GE:
                return l >= r ? 1 : 0;
        case EQ:
                return l == r ? 1 : 0;
        case NE:
                return l != r ? 1 : 0;
        case BITAND:
                return l & r;
        case BITXOR:
                return l ^ r;
        case BITOR:
                return l | r;
        default:
                lint_assert(false);
                /* NOTREACHED */
        }
}

static int64_t
fold_signed_integer(op_t op, int64_t l, int64_t r,
                    int64_t min_value, int64_t max_value, bool *overflow)
{
        switch (op) {
        case COMPL:
                return ~l;
        case UPLUS:
                return +l;
        case UMINUS:
                *overflow = l == min_value;
                return *overflow ? l : -l;
        case MULT:;
                uint64_t al = s64_abs(l);
                uint64_t ar = s64_abs(r);
                bool neg = (l >= 0) != (r >= 0);
                uint64_t max_prod = (uint64_t)max_value + (neg ? 1 : 0);
                if (al > 0 && ar > max_prod / al) {
                        *overflow = true;
                        return neg ? min_value : max_value;
                }
                return l * r;
        case DIV:
                if (r == 0) {
                        if (is_evaluation_mode(EM_EVAL))
                                /* division by 0 */
                                error(139);
                        return max_value;
                }
                if (l == min_value && r == -1) {
                        *overflow = true;
                        return l;
                }
                return l / r;
        case MOD:
                if (r == 0) {
                        if (is_evaluation_mode(EM_EVAL))
                                /* modulus by 0 */
                                error(140);
                        return 0;
                }
                if (l == min_value && r == -1) {
                        *overflow = true;
                        return 0;
                }
                return l % r;
        case PLUS:
                if (r > 0 && l > max_value - r) {
                        *overflow = true;
                        return max_value;
                }
                if (r < 0 && l < min_value - r) {
                        *overflow = true;
                        return min_value;
                }
                return l + r;
        case MINUS:
                if (r > 0 && l < min_value + r) {
                        *overflow = true;
                        return min_value;
                }
                if (r < 0 && l > max_value + r) {
                        *overflow = true;
                        return max_value;
                }
                return l - r;
        case SHL:
                /* TODO: warn about out-of-bounds 'r'. */
                /* TODO: warn about overflow. */
                return (int64_t)((uint64_t)l << (r & 63));
        case SHR:
                /* TODO: warn about out-of-bounds 'r'. */
                return s64_shr(l, r & 63);
        case LT:
                return l < r ? 1 : 0;
        case LE:
                return l <= r ? 1 : 0;
        case GT:
                return l > r ? 1 : 0;
        case GE:
                return l >= r ? 1 : 0;
        case EQ:
                return l == r ? 1 : 0;
        case NE:
                return l != r ? 1 : 0;
        case BITAND:
                return l & r;
        case BITXOR:
                return l ^ r;
        case BITOR:
                return l | r;
        default:
                lint_assert(false);
                /* NOTREACHED */
        }
}

static tnode_t *
fold_constant_integer(tnode_t *tn)
{

        lint_assert(has_operands(tn));
        tspec_t t = tn->u.ops.left->tn_type->t_tspec;
        int64_t l = tn->u.ops.left->u.value.u.integer;
        int64_t r = is_binary(tn) ? tn->u.ops.right->u.value.u.integer : 0;
        uint64_t mask = value_bits(size_in_bits(t));

        int64_t res;
        bool overflow = false;
        if (!is_integer(t) || is_uinteger(t)) {
                uint64_t u_res = fold_unsigned_integer(tn->tn_op,
                    (uint64_t)l, (uint64_t)r, mask, &overflow);
                if (u_res > mask)
                        overflow = true;
                res = (int64_t)u_res;
                if (overflow && hflag) {
                        char buf[128];
                        if (is_binary(tn)) {
                                snprintf(buf, sizeof(buf), "%ju %s %ju",
                                    (uintmax_t)l, op_name(tn->tn_op),
                                    (uintmax_t)r);
                        } else {
                                snprintf(buf, sizeof(buf), "%s%ju",
                                    op_name(tn->tn_op), (uintmax_t)l);
                        }
                        /* '%s' overflows '%s' */
                        warning(141, buf, expr_type_name(tn));
                }
        } else {
                int64_t max_value = (int64_t)(mask >> 1);
                int64_t min_value = -max_value - 1;
                res = fold_signed_integer(tn->tn_op,
                    l, r, min_value, max_value, &overflow);
                if (res < min_value || res > max_value)
                        overflow = true;
                if (overflow && hflag) {
                        char buf[128];
                        if (is_binary(tn)) {
                                snprintf(buf, sizeof(buf), "%jd %s %jd",
                                    (intmax_t)l, op_name(tn->tn_op),
                                    (intmax_t)r);
                        } else if (tn->tn_op == UMINUS && l < 0) {
                                snprintf(buf, sizeof(buf), "-(%jd)",
                                    (intmax_t)l);
                        } else {
                                snprintf(buf, sizeof(buf), "%s%jd",
                                    op_name(tn->tn_op), (intmax_t)l);
                        }
                        /* '%s' overflows '%s' */
                        warning(141, buf, expr_type_name(tn));
                }
        }

        val_t *v = xcalloc(1, sizeof(*v));
        v->v_tspec = tn->tn_type->t_tspec;
        v->u.integer = convert_integer(res, t, size_in_bits(t));

        tnode_t *cn = build_constant(tn->tn_type, v);
        if (tn->u.ops.left->tn_system_dependent)
                cn->tn_system_dependent = true;
        if (is_binary(tn) && tn->u.ops.right->tn_system_dependent)
                cn->tn_system_dependent = true;

        return cn;
}

static tnode_t *
build_struct_access(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
{

        lint_assert(rn->tn_op == NAME);
        lint_assert(is_member(rn->u.sym));

        bool lvalue = op == ARROW || ln->tn_lvalue;

        if (op == POINT)
                ln = build_address(sys, ln);
        else if (ln->tn_type->t_tspec != PTR) {
                lint_assert(!allow_c90);
                lint_assert(is_integer(ln->tn_type->t_tspec));
                ln = convert(NOOP, 0, expr_derive_ptr_type(gettyp(VOID)), ln);
        }

        tnode_t *ctn = build_integer_constant(PTRDIFF_TSPEC,
            rn->u.sym->u.s_member.sm_offset_in_bits / CHAR_SIZE);

        type_t *ptr_tp = expr_derive_ptr_type(rn->tn_type);
        tnode_t *ntn = build_op(PLUS, sys, ptr_tp, ln, ctn);
        if (ln->tn_op == CON)
                ntn = fold_constant_integer(ntn);

        op_t nop = rn->tn_type->t_bitfield ? FSEL : INDIR;
        ntn = build_op(nop, sys, ntn->tn_type->t_subt, ntn, NULL);
        if (!lvalue)
                ntn->tn_lvalue = false;

        return ntn;
}

static bool
may_be_signed_min(const tnode_t *tn)
{
        if (!is_integer(tn->tn_type->t_tspec))
                return false;
        if (is_uinteger(tn->tn_type->t_tspec))
                return false;
        integer_constraints c = ic_expr(tn);
        return c.smin == si_min_value(tn->tn_type);
}

/*
 * Get the size in bytes of type tp->t_subt, as a constant expression of type
 * ptrdiff_t as seen from the target platform.
 */
static tnode_t *
subt_size_in_bytes(type_t *tp)
{

        lint_assert(tp->t_tspec == PTR);
        tp = tp->t_subt;

        int elem = 1;
        while (tp->t_tspec == ARRAY) {
                elem *= tp->u.dimension;
                tp = tp->t_subt;
        }

        int elsz_in_bits = 0;
        switch (tp->t_tspec) {
        case FUNC:
                /* pointer to function is not allowed here */
                error(110);
                break;
        case VOID:
                /* cannot do pointer arithmetic on operand of unknown size */
                gnuism(136);
                break;
        case STRUCT:
        case UNION:
                if ((elsz_in_bits = (int)tp->u.sou->sou_size_in_bits) == 0)
                        /* cannot do pointer arithmetic on operand of ... */
                        error(136);
                break;
        case ENUM:
                if (is_incomplete(tp))
                        /* cannot do pointer arithmetic on operand of ... */
                        warning(136);
                /* FALLTHROUGH */
        default:
                if ((elsz_in_bits = size_in_bits(tp->t_tspec)) == 0)
                        /* cannot do pointer arithmetic on operand of ... */
                        error(136);
                else
                        lint_assert(elsz_in_bits != -1);
                break;
        }

        if (elem == 0 && elsz_in_bits != 0)
                /* cannot do pointer arithmetic on operand of unknown size */
                error(136);

        if (elsz_in_bits == 0)
                elsz_in_bits = CHAR_SIZE;

        return build_integer_constant(PTRDIFF_TSPEC,
            (int64_t)(elem * elsz_in_bits / CHAR_SIZE));
}

static tnode_t *
build_prepost_incdec(op_t op, bool sys, tnode_t *ln)
{

        lint_assert(ln != NULL);
        tnode_t *cn = ln->tn_type->t_tspec == PTR
            ? subt_size_in_bytes(ln->tn_type)
            : build_integer_constant(INT, 1);
        return build_op(op, sys, ln->tn_type, ln, cn);
}

static void
check_enum_array_index(const tnode_t *ln, const tnode_t *rn)
{

        if (ln->tn_op != ADDR)
                return;
        ln = ln->u.ops.left;
        if (ln->tn_op != NAME && ln->tn_op != STRING)
                return;

        const type_t *ltp = ln->tn_type;
        if (ltp->t_tspec != ARRAY || ltp->t_incomplete_array)
                return;

        if (rn->tn_op != CVT || !rn->tn_type->t_is_enum)
                return;
        if (rn->u.ops.left->tn_op != LOAD)
                return;

        const type_t *rtp = rn->u.ops.left->tn_type;
        const sym_t *ec = rtp->u.enumer->en_first_enumerator;
        const sym_t *max_ec = ec;
        lint_assert(ec != NULL);
        for (ec = ec->s_next; ec != NULL; ec = ec->s_next)
                if (ec->u.s_enum_constant > max_ec->u.s_enum_constant)
                        max_ec = ec;

        int64_t max_enum_value = max_ec->u.s_enum_constant;
        lint_assert(INT_MIN <= max_enum_value && max_enum_value <= INT_MAX);

        int max_array_index = ltp->u.dimension - 1;
        size_t nonnull_dimension = ln->tn_op == STRING
            ? str_len(ln)
            : ln->u.sym->u.s_array_nonnull_dimension;
        if (nonnull_dimension > 0)
                max_array_index = (int)nonnull_dimension - 1;
        if (max_enum_value == max_array_index)
                return;

        if (max_enum_value == max_array_index + 1 &&
            (strstr(max_ec->s_name, "MAX") != NULL ||
             strstr(max_ec->s_name, "max") != NULL ||
             strstr(max_ec->s_name, "NUM") != NULL ||
             strstr(max_ec->s_name, "num") != NULL ||
             strncmp(max_ec->s_name, "COUNT_", 6) == 0 ||
             str_ends_with(max_ec->s_name, "_COUNT") ||
             strncmp(max_ec->s_name, "LAST_", 5) == 0 ||
             str_ends_with(max_ec->s_name, "_end") ||
             strncmp(max_ec->s_name, "N_", 2) == 0))
                return;

        /* maximum value %d for '%s' of type '%s' does not match maximum array index %d */
        warning(348, (int)max_enum_value, max_ec->s_name, type_name(rtp),
            max_array_index);
        print_previous_declaration(max_ec);
}

static tnode_t *
build_plus_minus(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
{

        if (rn->tn_type->t_tspec == PTR && is_integer(ln->tn_type->t_tspec)) {
                tnode_t *tmp = ln;
                ln = rn;
                rn = tmp;
                /* pointer addition has integer on the left-hand side */
                query_message(5);
        }

        /* pointer +- integer */
        tspec_t lt = ln->tn_type->t_tspec;
        tspec_t rt = rn->tn_type->t_tspec;
        if (lt == PTR && rt != PTR) {
                lint_assert(is_integer(rt));

                check_ctype_macro_invocation(ln, rn);
                check_enum_array_index(ln, rn);

                tnode_t *elsz = subt_size_in_bytes(ln->tn_type);
                tspec_t szt = elsz->tn_type->t_tspec;
                if (rt != szt && rt != unsigned_type(szt))
                        rn = convert(NOOP, 0, elsz->tn_type, rn);

                tnode_t *prod = build_op(MULT, sys, rn->tn_type, rn, elsz);
                if (rn->tn_op == CON)
                        prod = fold_constant_integer(prod);

                return build_op(op, sys, ln->tn_type, ln, prod);
        }

        /* pointer - pointer */
        if (rt == PTR) {
                lint_assert(lt == PTR);
                lint_assert(op == MINUS);

                type_t *ptrdiff = gettyp(PTRDIFF_TSPEC);
                tnode_t *raw_diff = build_op(op, sys, ptrdiff, ln, rn);
                if (ln->tn_op == CON && rn->tn_op == CON)
                        raw_diff = fold_constant_integer(raw_diff);

                tnode_t *elsz = subt_size_in_bytes(ln->tn_type);
                balance(NOOP, &raw_diff, &elsz);

                return build_op(DIV, sys, ptrdiff, raw_diff, elsz);
        }

        return build_op(op, sys, ln->tn_type, ln, rn);
}

static tnode_t *
build_bit_shift(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
{

        if (!allow_c90 && rn->tn_type->t_tspec != INT)
                // XXX: C1978 7.5 says: "Both [operators] perform the usual
                // arithmetic conversions on their operands."
                // TODO: Add a test to exercise this part of the code.
                rn = convert(NOOP, 0, gettyp(INT), rn);
        return build_op(op, sys, ln->tn_type, ln, rn);
}

static bool
is_null_pointer(const tnode_t *tn)
{
        tspec_t t = tn->tn_type->t_tspec;

        // TODO: Investigate how other pointers are stored, in particular,
        // whether a pointer constant can have a non-zero value.
        // If not, simplify the code below.
        return ((t == PTR && tn->tn_type->t_subt->t_tspec == VOID)
                || is_integer(t))
            && (tn->tn_op == CON && tn->u.value.u.integer == 0);
}

/* Return a type based on tp1, with added qualifiers from tp2. */
static type_t *
merge_qualifiers(type_t *tp1, const type_t *tp2)
{

        lint_assert(tp1->t_tspec == PTR);
        lint_assert(tp2->t_tspec == PTR);

        bool c1 = tp1->t_subt->t_const;
        bool c2 = tp2->t_subt->t_const;
        bool v1 = tp1->t_subt->t_volatile;
        bool v2 = tp2->t_subt->t_volatile;

        if (c1 == (c1 | c2) && v1 == (v1 | v2))
                return tp1;

        type_t *nstp = expr_dup_type(tp1->t_subt);
        nstp->t_const |= c2;
        nstp->t_volatile |= v2;

        type_t *ntp = expr_dup_type(tp1);
        ntp->t_subt = nstp;
        return ntp;
}

/* See C99 6.5.15 "Conditional operator". */
static tnode_t *
build_colon(bool sys, tnode_t *ln, tnode_t *rn)
{
        tspec_t lt = ln->tn_type->t_tspec;
        tspec_t rt = rn->tn_type->t_tspec;

        type_t *tp;
        if (is_arithmetic(lt) && is_arithmetic(rt))
                /* The operands were already balanced in build_binary. */
                tp = ln->tn_type;
        else if (lt == BOOL && rt == BOOL)
                tp = ln->tn_type;
        else if (lt == VOID || rt == VOID)
                tp = gettyp(VOID);
        else if (is_struct_or_union(lt)) {
                lint_assert(is_struct_or_union(rt));
                lint_assert(ln->tn_type->u.sou == rn->tn_type->u.sou);
                if (is_incomplete(ln->tn_type)) {
                        /* unknown operand size, op '%s' */
                        error(138, op_name(COLON));
                        return NULL;
                }
                tp = ln->tn_type;
        } else if (lt == PTR && is_integer(rt)) {
                if (rt != PTRDIFF_TSPEC)
                        rn = convert(NOOP, 0, gettyp(PTRDIFF_TSPEC), rn);
                tp = ln->tn_type;
        } else if (rt == PTR && is_integer(lt)) {
                if (lt != PTRDIFF_TSPEC)
                        ln = convert(NOOP, 0, gettyp(PTRDIFF_TSPEC), ln);
                tp = rn->tn_type;
        } else if (lt == PTR && is_null_pointer(rn))
                tp = merge_qualifiers(ln->tn_type, rn->tn_type);
        else if (rt == PTR && is_null_pointer(ln))
                tp = merge_qualifiers(rn->tn_type, ln->tn_type);
        else if (lt == PTR && ln->tn_type->t_subt->t_tspec == VOID)
                tp = merge_qualifiers(ln->tn_type, rn->tn_type);
        else if (rt == PTR && rn->tn_type->t_subt->t_tspec == VOID)
                tp = merge_qualifiers(rn->tn_type, ln->tn_type);
        else {
                /*
                 * XXX For now we simply take the left type. This is probably
                 * wrong, if one type contains a function prototype and the
                 * other one, at the same place, only an old-style declaration.
                 */
                tp = merge_qualifiers(ln->tn_type, rn->tn_type);
        }

        return build_op(COLON, sys, tp, ln, rn);
}

/* TODO: check for varargs */
static bool
is_cast_redundant(const tnode_t *tn)
{
        const type_t *ntp = tn->tn_type, *otp = tn->u.ops.left->tn_type;
        tspec_t nt = ntp->t_tspec, ot = otp->t_tspec;

        if (nt == BOOL || ot == BOOL)
                return nt == BOOL && ot == BOOL;

        if (is_integer(nt) && is_integer(ot)) {
                unsigned int nw = width_in_bits(ntp), ow = width_in_bits(otp);
                if (is_uinteger(nt) == is_uinteger(ot))
                        return nw >= ow;
                return is_uinteger(ot) && nw > ow;
        }

        if (is_complex(nt) || is_complex(ot))
                return is_complex(nt) && is_complex(ot) &&
                    size_in_bits(nt) >= size_in_bits(ot);

        if (is_floating(nt) && is_floating(ot))
                return size_in_bits(nt) >= size_in_bits(ot);

        if (nt == PTR && ot == PTR) {
                if (!ntp->t_subt->t_const && otp->t_subt->t_const)
                        return false;
                if (!ntp->t_subt->t_volatile && otp->t_subt->t_volatile)
                        return false;

                if (ntp->t_subt->t_tspec == VOID ||
                    otp->t_subt->t_tspec == VOID ||
                    types_compatible(ntp->t_subt, otp->t_subt,
                        false, false, NULL))
                        return true;
        }

        return false;
}

static bool
is_assignment(op_t op)
{

        return op == ASSIGN ||
            op == MULASS ||
            op == DIVASS ||
            op == MODASS ||
            op == ADDASS ||
            op == SUBASS ||
            op == SHLASS ||
            op == SHRASS ||
            op == ANDASS ||
            op == XORASS ||
            op == ORASS ||
            op == RETURN ||
            op == INIT;
}

static tnode_t *
build_assignment(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
{

        tspec_t lt = ln->tn_type->t_tspec;
        tspec_t rt = rn->tn_type->t_tspec;

        if (is_assignment(rn->tn_op))
                /* chained assignment with '%s' and '%s' */
                query_message(10, op_name(op), op_name(rn->tn_op));

        if ((op == ADDASS || op == SUBASS) && lt == PTR) {
                lint_assert(is_integer(rt));
                tnode_t *ctn = subt_size_in_bytes(ln->tn_type);
                if (rn->tn_type->t_tspec != ctn->tn_type->t_tspec)
                        rn = convert(NOOP, 0, ctn->tn_type, rn);
                rn = build_op(MULT, sys, rn->tn_type, rn, ctn);
                if (rn->u.ops.left->tn_op == CON)
                        rn = fold_constant_integer(rn);
        }

        if ((op == ASSIGN || op == RETURN || op == INIT) &&
            (lt == STRUCT || rt == STRUCT)) {
                lint_assert(lt == rt);
                lint_assert(ln->tn_type->u.sou == rn->tn_type->u.sou);
                if (is_incomplete(ln->tn_type)) {
                        if (op == RETURN)
                                /* cannot return incomplete type */
                                error(212);
                        else
                                /* unknown operand size, op '%s' */
                                error(138, op_name(op));
                        return NULL;
                }
        }

        if (op == SHLASS && hflag && allow_trad && allow_c90
            && portable_rank_cmp(lt, rt) < 0)
                /* '%s' %s '%s' differs between traditional C and C90 */
                warning(118, tspec_name(lt), "<<=", tspec_name(rt));

        if (op != SHLASS && op != SHRASS
            && (op == ASSIGN || lt != PTR)
            && (lt != rt || (ln->tn_type->t_bitfield && rn->tn_op == CON))) {
                rn = convert(op, 0, ln->tn_type, rn);
                rt = lt;
        }

        if (lt == PTR && ln->tn_type->t_subt->t_tspec != VOID
            && rt == PTR && rn->tn_type->t_subt->t_tspec == VOID
            && !is_null_pointer(rn))
                /* implicit narrowing conversion from void ... */
                query_message(20, type_name(ln->tn_type));

        if (any_query_enabled && rn->tn_op == CVT && rn->tn_cast &&
            types_compatible(ln->tn_type, rn->tn_type, false, false, NULL) &&
            is_cast_redundant(rn)) {
                /* redundant cast from '%s' to '%s' before assignment */
                query_message(7, expr_type_name(rn->u.ops.left),
                    type_name(rn->tn_type));
        }

        return build_op(op, sys, ln->tn_type, ln, rn);
}

static tnode_t *
build_real_imag(op_t op, bool sys, tnode_t *ln)
{

        lint_assert(ln != NULL);
        if (ln->tn_op == NAME) {
                /*
                 * This may be too much, but it avoids wrong warnings. See
                 * d_c99_complex_split.c.
                 */
                mark_as_used(ln->u.sym, false, false);
                mark_as_set(ln->u.sym);
        }

        tspec_t t;
        switch (ln->tn_type->t_tspec) {
        case LCOMPLEX:
                t = LDOUBLE;
                break;
        case DCOMPLEX:
                t = DOUBLE;
                break;
        case FCOMPLEX:
                t = FLOAT;
                break;
        default:
                /* '__%s__' is invalid for type '%s' */
                error(276, op == REAL ? "real" : "imag",
                    type_name(ln->tn_type));
                return NULL;
        }

        tnode_t *ntn = build_op(op, sys, gettyp(t), ln, NULL);
        ntn->tn_lvalue = true;
        return ntn;
}

static bool
is_confusing_precedence(op_t op, const tnode_t *operand, op_t *cop)
{
        if (operand->tn_parenthesized)
                return false;
        op_t oop = operand->tn_op;

        if (op == SHL || op == SHR) {
                if (oop == PLUS || oop == MINUS)
                        return *cop = oop, true;
                return false;
        }

        if (op == LOGOR) {
                if (oop == LOGAND)
                        return *cop = oop, true;
                return false;
        }

        lint_assert(op == BITAND || op == BITXOR || op == BITOR);
        if (oop != op
            && (oop == PLUS || oop == MINUS || oop == BITAND || oop == BITXOR))
                return *cop = oop, true;
        return false;
}

/*
 * Print a warning if the given node has operands which should be
 * parenthesized.
 *
 * XXX Does not work if an operand is a constant expression. Constant
 * expressions are already folded.
 */
static void
check_precedence_confusion(tnode_t *tn)
{
        tnode_t *ln, *rn;

        if (!hflag)
                return;

        debug_node(tn);

        lint_assert(is_binary(tn));
        for (ln = tn->u.ops.left; ln->tn_op == CVT; ln = ln->u.ops.left)
                continue;
        for (rn = tn->u.ops.right; rn->tn_op == CVT; rn = rn->u.ops.left)
                continue;

        op_t cop;
        if (is_confusing_precedence(tn->tn_op, ln, &cop) ||
            is_confusing_precedence(tn->tn_op, rn, &cop)) {
                /* possible precedence confusion between '%s' and '%s' */
                warning(169, op_name(tn->tn_op), op_name(cop));
        }
}

static tnode_t *
fold_constant_compare_zero(tnode_t *tn)
{

        val_t *v = xcalloc(1, sizeof(*v));
        v->v_tspec = tn->tn_type->t_tspec;
        lint_assert(v->v_tspec == INT || (Tflag && v->v_tspec == BOOL));

        lint_assert(has_operands(tn));
        bool l = constant_is_nonzero(tn->u.ops.left);
        bool r = is_binary(tn) && constant_is_nonzero(tn->u.ops.right);

        switch (tn->tn_op) {
        case NOT:
                v->u.integer = !l ? 1 : 0;
                break;
        case LOGAND:
                v->u.integer = l && r ? 1 : 0;
                break;
        case LOGOR:
                v->u.integer = l || r ? 1 : 0;
                break;
        default:
                lint_assert(false);
        }

        return build_constant(tn->tn_type, v);
}

static long double
floating_error_value(tspec_t t, long double lv)
{
        if (t == FLOAT)
                return lv < 0 ? -FLT_MAX : FLT_MAX;
        if (t == DOUBLE)
                return lv < 0 ? -DBL_MAX : DBL_MAX;
        /*
         * When NetBSD is cross-built in MKLINT=yes mode on x86_64 for sparc64,
         * tools/lint checks this code while building usr.bin/xlint. In that
         * situation, lint uses the preprocessor for sparc64, in which the type
         * 'long double' is IEEE-754-binary128, affecting the macro LDBL_MAX
         * below. The type 'long double', as well as the strtold
         * implementation, comes from the host platform x86_64 though, where
         * 'long double' consumes 128 bits as well but only uses 80 of them.
         * The exponent range of the two 'long double' types is the same, but
         * the maximum finite value differs due to the extended precision on
         * sparc64.
         *
         * To properly handle the data types of the target platform, lint would
         * have to implement the floating-point types in a platform-independent
         * way, which is not worth the effort, given how few programs
         * practically use 'long double'.
         */
        /* LINTED 248: floating-point constant out of range */
        long double max = LDBL_MAX;
        return lv < 0 ? -max : max;
}

static bool
is_floating_overflow(tspec_t t, long double val)
{
        if (fpe != 0 || isfinite(val) == 0)
                return true;
        if (t == FLOAT && (val > FLT_MAX || val < -FLT_MAX))
                return true;
        if (t == DOUBLE && (val > DBL_MAX || val < -DBL_MAX))
                return true;
        return false;
}

static tnode_t *
fold_constant_floating(tnode_t *tn)
{

        fpe = 0;

        tspec_t t = tn->tn_type->t_tspec;

        val_t *v = xcalloc(1, sizeof(*v));
        v->v_tspec = t;

        lint_assert(is_floating(t));
        lint_assert(has_operands(tn));
        lint_assert(t == tn->u.ops.left->tn_type->t_tspec);
        lint_assert(!is_binary(tn) || t == tn->u.ops.right->tn_type->t_tspec);

        long double lv = tn->u.ops.left->u.value.u.floating;
        long double rv = is_binary(tn) ? tn->u.ops.right->u.value.u.floating
            : 0.0;

        switch (tn->tn_op) {
        case UPLUS:
                v->u.floating = lv;
                break;
        case UMINUS:
                v->u.floating = -lv;
                break;
        case MULT:
                v->u.floating = lv * rv;
                break;
        case DIV:
                if (rv == 0.0) {
                        if (is_evaluation_mode(EM_EVAL))
                                /* division by 0 */
                                error(139);
                        v->u.floating = floating_error_value(t, lv);
                } else {
                        v->u.floating = lv / rv;
                }
                break;
        case PLUS:
                v->u.floating = lv + rv;
                break;
        case MINUS:
                v->u.floating = lv - rv;
                break;
        case LT:
                v->u.integer = lv < rv ? 1 : 0;
                break;
        case LE:
                v->u.integer = lv <= rv ? 1 : 0;
                break;
        case GE:
                v->u.integer = lv >= rv ? 1 : 0;
                break;
        case GT:
                v->u.integer = lv > rv ? 1 : 0;
                break;
        case EQ:
                v->u.integer = lv == rv ? 1 : 0;
                break;
        case NE:
                v->u.integer = lv != rv ? 1 : 0;
                break;
        default:
                lint_assert(false);
        }

        // XXX: Must not access u.floating after setting u.integer.
        lint_assert(fpe != 0 || isnan(v->u.floating) == 0);
        if (is_complex(v->v_tspec)) {
                /*
                 * Don't warn, as lint doesn't model the imaginary part of
                 * complex numbers.
                 */
                fpe = 0;
        } else if (is_floating_overflow(t, v->u.floating)) {
                /* operator '%s' produces floating point overflow */
                warning(142, op_name(tn->tn_op));
                v->u.floating = floating_error_value(t, v->u.floating);
                fpe = 0;
        }

        return build_constant(tn->tn_type, v);
}

static void
use(const tnode_t *tn)
{
        if (tn == NULL)
                return;
        switch (tn->tn_op) {
        case NAME:
                mark_as_used(tn->u.sym, false /* XXX */, false /* XXX */);
                break;
        case CON:
        case STRING:
                break;
        case CALL:;
                const function_call *call = tn->u.call;
                for (size_t i = 0, n = call->args_len; i < n; i++)
                        use(call->args[i]);
                break;
        default:
                lint_assert(has_operands(tn));
                use(tn->u.ops.left);
                if (is_binary(tn))
                        use(tn->u.ops.right);
        }
}

/*
 * Create a tree node for a binary operator and its two operands. Also called
 * for unary operators; in that case rn is NULL.
 *
 * Function calls, sizeof and casts are handled elsewhere.
 */
tnode_t *
build_binary(tnode_t *ln, op_t op, bool sys, tnode_t *rn)
{
        const mod_t *mp = &modtab[op];

        /* If there was an error in one of the operands, return. */
        if (ln == NULL || (mp->m_binary && rn == NULL))
                return NULL;

        if (mp->m_value_context || mp->m_compares_with_zero)
                ln = cconv(ln);
        if (mp->m_binary && op != ARROW && op != POINT)
                rn = cconv(rn);

        if (mp->m_comparison)
                check_integer_comparison(op, ln, rn);

        if (mp->m_value_context || mp->m_compares_with_zero)
                ln = promote(op, false, ln);
        if (mp->m_binary && op != ARROW && op != POINT &&
            op != ASSIGN && op != RETURN && op != INIT)
                rn = promote(op, false, rn);

        if (mp->m_warn_if_left_unsigned_in_c90 &&
            ln->tn_op == CON && ln->u.value.v_unsigned_since_c90) {
                /* C90 treats constant as unsigned, op '%s' */
                warning(218, op_name(op));
                ln->u.value.v_unsigned_since_c90 = false;
        }
        if (mp->m_warn_if_right_unsigned_in_c90 &&
            rn->tn_op == CON && rn->u.value.v_unsigned_since_c90) {
                /* C90 treats constant as unsigned, op '%s' */
                warning(218, op_name(op));
                rn->u.value.v_unsigned_since_c90 = false;
        }

        if (mp->m_balance_operands || (!allow_c90 && (op == SHL || op == SHR)))
                balance(op, &ln, &rn);

        if (!typeok(op, NULL, 0, ln, rn))
                return NULL;

        tnode_t *ntn;
        switch (op) {
        case POINT:
        case ARROW:
                ntn = build_struct_access(op, sys, ln, rn);
                break;
        case UMINUS:
                if (any_query_enabled && may_be_signed_min(ln))
                        /* negation of signed '%s' */
                        query_message(25, expr_type_name(ln));
                ntn = build_op(op, sys, ln->tn_type, ln, rn);
                break;
        case INCAFT:
        case DECAFT:
        case INCBEF:
        case DECBEF:
                ntn = build_prepost_incdec(op, sys, ln);
                break;
        case ADDR:
                ntn = build_address(sys, ln);
                break;
        case INDIR:
                ntn = build_op(INDIR, sys, ln->tn_type->t_subt, ln, NULL);
                break;
        case PLUS:
        case MINUS:
                ntn = build_plus_minus(op, sys, ln, rn);
                break;
        case SHL:
        case SHR:
                ntn = build_bit_shift(op, sys, ln, rn);
                break;
        case COLON:
                ntn = build_colon(sys, ln, rn);
                break;
        case ASSIGN:
        case MULASS:
        case DIVASS:
        case MODASS:
        case ADDASS:
        case SUBASS:
        case SHLASS:
        case SHRASS:
        case ANDASS:
        case XORASS:
        case ORASS:
        case RETURN:
        case INIT:
                ntn = build_assignment(op, sys, ln, rn);
                break;
        case COMMA:
                /* comma operator with types '%s' and '%s' */
                query_message(12,
                    expr_type_name(ln), expr_type_name(rn));
                /* FALLTHROUGH */
        case QUEST:
                ntn = build_op(op, sys, rn->tn_type, ln, rn);
                break;
        case REAL:
        case IMAG:
                ntn = build_real_imag(op, sys, ln);
                break;
        default:
                lint_assert(mp->m_binary == (rn != NULL));
                if ((op == NOT || op == LOGAND || op == LOGOR)
                    && ln->tn_op == ASSIGN && ln->u.ops.right->tn_op == CON) {
                        /* constant assignment of type '%s' in operand ... */
                        warning(382, expr_type_name(ln), op_name(op),
                            is_nonzero_val(&ln->u.ops.right->u.value)
                            ? "true" : "false");
                }
                if ((op == LOGAND || op == LOGOR)
                    && rn->tn_op == ASSIGN && rn->u.ops.right->tn_op == CON) {
                        /* constant assignment of type '%s' in operand ... */
                        warning(382, expr_type_name(rn), op_name(op),
                            is_nonzero_val(&rn->u.ops.right->u.value)
                            ? "true" : "false");
                }
                type_t *rettp = mp->m_returns_bool
                    ? gettyp(Tflag ? BOOL : INT) : ln->tn_type;
                ntn = build_op(op, sys, rettp, ln, rn);
                break;
        }

        if (ntn == NULL)
                return NULL;

        if (mp->m_possible_precedence_confusion)
                check_precedence_confusion(ntn);

        if (mp->m_fold_constant_operands && ln->tn_op == CON) {
                if (!mp->m_binary || rn->tn_op == CON) {
                        if (mp->m_compares_with_zero)
                                ntn = fold_constant_compare_zero(ntn);
                        else if (is_floating(ntn->tn_type->t_tspec))
                                ntn = fold_constant_floating(ntn);
                        else
                                ntn = fold_constant_integer(ntn);
                } else if (op == QUEST) {
                        lint_assert(has_operands(rn));
                        use(ln->u.value.u.integer != 0
                            ? rn->u.ops.right : rn->u.ops.left);
                        ntn = ln->u.value.u.integer != 0
                            ? rn->u.ops.left : rn->u.ops.right;
                }
        }

        return ntn;
}

tnode_t *
build_unary(op_t op, bool sys, tnode_t *tn)
{
        return build_binary(tn, op, sys, NULL);
}

static bool
are_members_compatible(const sym_t *a, const sym_t *b)
{
        if (a->u.s_member.sm_offset_in_bits != b->u.s_member.sm_offset_in_bits)
                return false;

        const type_t *atp = a->s_type;
        const type_t *btp = b->s_type;
        bool w = false;
        if (!types_compatible(atp, btp, false, false, &w) && !w)
                return false;
        if (a->s_bitfield != b->s_bitfield)
                return false;
        if (a->s_bitfield) {
                if (atp->t_bit_field_width != btp->t_bit_field_width)
                        return false;
                if (atp->t_bit_field_offset != btp->t_bit_field_offset)
                        return false;
        }
        return true;
}

/*
 * Return whether all struct/union members with the same name have the same
 * type and offset.
 */
static bool
all_members_compatible(const sym_t *msym)
{
        for (const sym_t *csym = msym;
            csym != NULL; csym = csym->s_symtab_next) {
                if (!is_member(csym))
                        continue;
                if (strcmp(msym->s_name, csym->s_name) != 0)
                        continue;

                for (const sym_t *sym = csym->s_symtab_next;
                    sym != NULL; sym = sym->s_symtab_next) {
                        if (is_member(sym)
                            && strcmp(csym->s_name, sym->s_name) == 0
                            && !are_members_compatible(csym, sym))
                                return false;
                }
        }
        return true;
}

sym_t *
find_member(const struct_or_union *sou, const char *name)
{
        for (sym_t *mem = sou->sou_first_member;
            mem != NULL; mem = mem->s_next) {
                lint_assert(is_member(mem));
                lint_assert(mem->u.s_member.sm_containing_type == sou);
                if (strcmp(mem->s_name, name) == 0)
                        return mem;
        }

        for (sym_t *mem = sou->sou_first_member;
            mem != NULL; mem = mem->s_next) {
                if (is_struct_or_union(mem->s_type->t_tspec)
                    && mem->s_name == unnamed) {
                        sym_t *nested_mem =
                            find_member(mem->s_type->u.sou, name);
                        if (nested_mem != NULL)
                                return nested_mem;
                }
        }
        return NULL;
}

/*
 * Remove the member if it was unknown until now, which means
 * that no defined struct or union has a member with the same name.
 */
static void
remove_unknown_member(tnode_t *tn, sym_t *msym)
{
        /* type '%s' does not have member '%s' */
        error(101, type_name(tn->tn_type), msym->s_name);
        symtab_remove_forever(msym);
        msym->s_kind = SK_MEMBER;
        msym->s_scl = STRUCT_MEMBER;

        struct_or_union *sou = expr_zero_alloc(sizeof(*sou),
            "struct_or_union");
        sou->sou_tag = expr_zero_alloc(sizeof(*sou->sou_tag), "sym");
        sou->sou_tag->s_name = unnamed;

        msym->u.s_member.sm_containing_type = sou;
        /*
         * The member sm_offset_in_bits is not needed here since this symbol
         * can only be used for error reporting.
         */
}

/*
 * Returns a symbol which has the same name as 'msym' and is a member of the
 * struct or union specified by 'tn'.
 */
static sym_t *
struct_or_union_member(tnode_t *tn, op_t op, sym_t *msym)
{

        /* Determine the tag type of which msym is expected to be a member. */
        const type_t *tp = NULL;
        if (op == POINT && is_struct_or_union(tn->tn_type->t_tspec))
                tp = tn->tn_type;
        if (op == ARROW && tn->tn_type->t_tspec == PTR
            && is_struct_or_union(tn->tn_type->t_subt->t_tspec))
                tp = tn->tn_type->t_subt;
        struct_or_union *sou = tp != NULL ? tp->u.sou : NULL;

        if (sou != NULL) {
                sym_t *nested_mem = find_member(sou, msym->s_name);
                if (nested_mem != NULL)
                        return nested_mem;
        }

        if (msym->s_scl == NO_SCL) {
                remove_unknown_member(tn, msym);
                return msym;
        }

        bool eq = all_members_compatible(msym);

        /*
         * Now handle the case in which the left operand refers really to a
         * struct/union, but the right operand is not member of it.
         */
        if (sou != NULL) {
                if (eq && !allow_c90)
                        /* invalid use of member '%s' */
                        warning(102, msym->s_name);
                else
                        /* invalid use of member '%s' */
                        error(102, msym->s_name);
                return msym;
        }

        if (eq) {
                if (op == POINT) {
                        if (!allow_c90)
                                /* left operand of '.' must be struct ... */
                                warning(103, expr_type_name(tn));
                        else
                                /* left operand of '.' must be struct ... */
                                error(103, expr_type_name(tn));
                } else {
                        if (!allow_c90 && tn->tn_type->t_tspec == PTR)
                                /* left operand of '->' must be pointer ... */
                                warning(104, expr_type_name(tn));
                        else
                                /* left operand of '->' must be pointer ... */
                                error(104, expr_type_name(tn));
                }
        } else {
                if (!allow_c90)
                        /* non-unique member requires struct/union %s */
                        error(105, op == POINT ? "object" : "pointer");
                else
                        /* unacceptable operand of '%s' */
                        error(111, op_name(op));
        }

        return msym;
}

tnode_t *
build_member_access(tnode_t *ln, op_t op, bool sys, sbuf_t *member)
{
        sym_t *msym;

        if (ln == NULL)
                return NULL;

        if (op == ARROW)
                /* must do this before struct_or_union_member is called */
                ln = cconv(ln);
        msym = struct_or_union_member(ln, op, getsym(member));
        return build_binary(ln, op, sys, build_name(msym, false));
}

/*
 * Perform class conversions.
 *
 * Arrays of type T are converted into pointers to type T.
 * Functions are converted to pointers to functions.
 * Lvalues are converted to rvalues.
 *
 * C99 6.3 "Conversions"
 * C99 6.3.2 "Other operands"
 * C99 6.3.2.1 "Lvalues, arrays, and function designators"
 */
tnode_t *
cconv(tnode_t *tn)
{
        if (tn->tn_type->t_tspec == ARRAY) {
                if (!tn->tn_lvalue) {
                        /* XXX print correct operator */
                        /* %soperand of '%s' must be lvalue */
                        gnuism(114, "", op_name(ADDR));
                }
                tn = build_op(ADDR, tn->tn_sys,
                    expr_derive_ptr_type(tn->tn_type->t_subt), tn, NULL);
        }

        if (tn->tn_type->t_tspec == FUNC)
                tn = build_address(tn->tn_sys, tn);

        if (tn->tn_lvalue) {
                type_t *tp = expr_dup_type(tn->tn_type);
                /* C99 6.3.2.1p2 sentence 2 says to remove the qualifiers. */
                tp->t_const = tp->t_volatile = false;
                tn = build_op(LOAD, tn->tn_sys, tp, tn, NULL);
        }

        return tn;
}

const tnode_t *
before_conversion(const tnode_t *tn)
{
        while (tn->tn_op == CVT && !tn->tn_cast)
                tn = tn->u.ops.left;
        return tn;
}

/*
 * Most errors required by C90 are reported in struct_or_union_member().
 * Here we only check for totally wrong things.
 */
static bool
typeok_point(const tnode_t *ln, const type_t *ltp, tspec_t lt)
{
        if (is_struct_or_union(lt))
                return true;

        if (lt == FUNC || lt == VOID || ltp->t_bitfield)
                goto wrong;

        /*
         * Some C dialects from before C90 tolerated any lvalue on the
         * left-hand side of the '.' operator, allowing things like 'char
         * st[100]; st.st_mtime', assuming that the member 'st_mtime' only
         * occurred in a single struct; see typeok_arrow.
         */
        if (ln->tn_lvalue)
                return true;

wrong:
        /* With allow_c90 we already got an error */
        if (!allow_c90)
                /* unacceptable operand of '%s' */
                error(111, op_name(POINT));

        return false;
}

static bool
typeok_arrow(tspec_t lt)
{
        /*
         * C1978 Appendix A 14.1 says: <quote>In fact, any lvalue is allowed
         * before '.', and that lvalue is then assumed to have the form of the
         * structure of which the name of the right is a member. [...] Such
         * constructions are non-portable.</quote>
         */
        if (lt == PTR || (!allow_c90 && is_integer(lt)))
                return true;

        /* With allow_c90 we already got an error */
        if (!allow_c90)
                /* unacceptable operand of '%s' */
                error(111, op_name(ARROW));
        return false;
}

static bool
typeok_incdec(op_t op, const tnode_t *tn, const type_t *tp)
{
        /* operand has scalar type (checked in typeok) */
        if (!tn->tn_lvalue) {
                if (tn->tn_op == CVT && tn->tn_cast &&
                    tn->u.ops.left->tn_op == LOAD)
                        /* a cast does not yield an lvalue */
                        error(163);
                /* %soperand of '%s' must be lvalue */
                error(114, "", op_name(op));
                return false;
        }
        if (tp->t_const && allow_c90)
                /* %soperand of '%s' must be modifiable lvalue */
                warning(115, "", op_name(op));
        return true;
}

static bool
typeok_address(op_t op, const tnode_t *tn, const type_t *tp, tspec_t t)
{
        if (t == ARRAY || t == FUNC) {
                /* ok, a warning comes later (in build_address()) */
        } else if (!tn->tn_lvalue) {
                if (tn->tn_op == CVT && tn->tn_cast &&
                    tn->u.ops.left->tn_op == LOAD)
                        /* a cast does not yield an lvalue */
                        error(163);
                /* %soperand of '%s' must be lvalue */
                error(114, "", op_name(op));
                return false;
        } else if (is_scalar(t)) {
                if (tp->t_bitfield) {
                        /* cannot take address of bit-field */
                        error(112);
                        return false;
                }
        } else if (t != STRUCT && t != UNION) {
                /* unacceptable operand of '%s' */
                error(111, op_name(op));
                return false;
        }
        if (tn->tn_op == NAME && tn->u.sym->s_register) {
                /* cannot take address of register '%s' */
                error(113, tn->u.sym->s_name);
                return false;
        }
        return true;
}

static bool
typeok_indir(const type_t *tp, tspec_t t)
{

        if (t != PTR) {
                /* cannot dereference non-pointer type '%s' */
                error(96, type_name(tp));
                return false;
        }
        return true;
}

static void
warn_incompatible_types(op_t op,
                        const type_t *ltp, tspec_t lt,
                        const type_t *rtp, tspec_t rt)
{
        bool binary = modtab[op].m_binary;

        if (lt == VOID || (binary && rt == VOID)) {
                /* void type invalid in expression */
                error(109);
        } else if (op == ASSIGN)
                /* cannot assign to '%s' from '%s' */
                error(171, type_name(ltp), type_name(rtp));
        else if (binary)
                /* operands of '%s' have incompatible types '%s' and '%s' */
                error(107, op_name(op), type_name(ltp), type_name(rtp));
        else {
                lint_assert(rt == NO_TSPEC);
                /* operand of '%s' has invalid type '%s' */
                error(108, op_name(op), type_name(ltp));
        }
}

static bool
typeok_plus(op_t op,
            const type_t *ltp, tspec_t lt,
            const type_t *rtp, tspec_t rt)
{
        /* operands have scalar types (checked in typeok) */
        if ((lt == PTR && !is_integer(rt)) || (rt == PTR && !is_integer(lt))) {
                warn_incompatible_types(op, ltp, lt, rtp, rt);
                return false;
        }
        return true;
}

static bool
typeok_minus(op_t op,
             const type_t *ltp, tspec_t lt,
             const type_t *rtp, tspec_t rt)
{
        /* operands have scalar types (checked in typeok) */
        if ((lt == PTR && rt != PTR && !is_integer(rt)) ||
            (lt != PTR && rt == PTR)) {
                warn_incompatible_types(op, ltp, lt, rtp, rt);
                return false;
        }
        if (lt == PTR && rt == PTR &&
            !types_compatible(ltp->t_subt, rtp->t_subt, true, false, NULL)) {
                /* invalid pointer subtraction */
                error(116);
        }
        return true;
}

static void
typeok_shr(const tnode_t *ln, tspec_t lt,
           const tnode_t *rn, tspec_t rt)
{
        tspec_t olt = before_conversion(ln)->tn_type->t_tspec;
        tspec_t ort = before_conversion(rn)->tn_type->t_tspec;

        if (is_uinteger(olt))
                return;

        if (pflag) {
                integer_constraints lc = ic_expr(ln);
                if (lc.bclr >> 63 != 0)
                        return;

                if (ln->tn_op != CON)
                        /* bitwise '%s' on signed '%s' possibly nonportable */
                        warning(117, ">>", expr_type_name(ln));
                else if (ln->u.value.u.integer < 0)
                        /* bitwise '%s' on signed '%s' nonportable */
                        warning(120, ">>", expr_type_name(ln));
                return;
        }

        /* The left operand would become unsigned in traditional C. */
        if (allow_trad && allow_c90 && hflag && is_uinteger(ort)
            && !(ln->tn_op == CON && ln->u.value.u.integer >= 0))
                /* '%s' %s '%s' differs between traditional C and C90 */
                warning(118, tspec_name(lt), ">>", tspec_name(rt));

        /*
         * In traditional C, the left operand would be extended
         * (possibly sign-extended) and then shifted.
         */
        if (allow_trad && allow_c90 && hflag && !is_uinteger(ort)
            && portable_rank_cmp(lt, rt) < 0
            && !(ln->tn_op == CON && ln->u.value.u.integer >= 0))
                /* '%s' %s '%s' differs between traditional C and C90 */
                warning(118, tspec_name(lt), ">>", tspec_name(rt));
}

// C90 does not mention signed shift-left. Later standards mention that case
// but leave open whether 'uint8_t << 24' is supposed to have an unsigned or a
// signed result type. It depends on whether E1 is interpreted to be the left
// operand's type before or after integral promotions.
static void
typeok_shl_signed_to_msb(const tnode_t *ln, const tnode_t *rn)
{
        integer_constraints lc = ic_expr(ln);
        int64_t n;
        unsigned lw = width_in_bits(ln->tn_type);
        if (!is_uinteger(ln->tn_type->t_tspec)
            && ln->tn_op != CON
            && ((lc.smin == 0 && lc.smax != 0 && lc.smax != INT64_MAX
                    && (lc.smax & (lc.smax + 1)) == 0)
                || (lc.smin != INT64_MAX && lc.smax != INT64_MIN
                    && lc.smin + 1 == -lc.smax))
            && rn->tn_op == CON
            && (n = rn->u.value.u.integer, 1 <= n && n <= lw)
            && u64_width((uint64_t)lc.smax - (uint64_t)lc.smin) + n == lw)
                /* bitwise '%s' on signed '%s' possibly nonportable */
                warning(117, "<<", expr_type_name(ln));
}

static void
typeok_shl(const tnode_t *ln, tspec_t lt, const tnode_t *rn, tspec_t rt)
{
        /*
         * Traditional C performs the usual arithmetic conversions on the
         * operands, C90 and later don't.
         */
        if (hflag && allow_trad && allow_c90 && portable_rank_cmp(lt, rt) < 0)
                /* '%s' %s '%s' differs between traditional C and C90 */
                warning(118, tspec_name(lt), "<<", tspec_name(rt));

        typeok_shl_signed_to_msb(ln, rn);
}

static void
typeok_shift(const tnode_t *ln, tspec_t lt, const tnode_t *rn, tspec_t rt)
{
        if (rn->tn_op != CON)
                return;

        if (!is_uinteger(rt) && rn->u.value.u.integer < 0)
                /* negative shift */
                warning(121);
        else if ((uint64_t)rn->u.value.u.integer == size_in_bits(lt))
                /* shift amount %u equals bit-size of '%s' */
                warning(267,
                    (unsigned)rn->u.value.u.integer, expr_type_name(ln));
        else if ((uint64_t)rn->u.value.u.integer > size_in_bits(lt)) {
                /* shift amount %llu is greater than bit-size %llu of '%s' */
                warning(122, (unsigned long long)rn->u.value.u.integer,
                    (unsigned long long)size_in_bits(lt),
                    expr_type_name(ln));
        }
}

static bool
is_typeok_eq(const tnode_t *ln, tspec_t lt, const tnode_t *rn, tspec_t rt)
{
        if (lt == PTR && is_null_pointer(rn))
                return true;
        if (rt == PTR && is_null_pointer(ln))
                return true;
        return false;
}

static void
warn_incompatible_pointers(op_t op, const type_t *ltp, const type_t *rtp)
{
        lint_assert(ltp->t_tspec == PTR);
        lint_assert(rtp->t_tspec == PTR);

        tspec_t lt = ltp->t_subt->t_tspec;
        tspec_t rt = rtp->t_subt->t_tspec;

        if (is_struct_or_union(lt) && is_struct_or_union(rt)) {
                if (op == RETURN)
                        /* invalid structure pointer combination */
                        warning(244);
                else {
                        /* incompatible structure pointers: '%s' '%s' '%s' */
                        warning(245, type_name(ltp),
                            op_name(op), type_name(rtp));
                }
        } else {
                if (op == RETURN)
                        /* invalid combination of '%s' and '%s' */
                        warning(184, type_name(ltp), type_name(rtp));
                else {
                        /* invalid combination of '%s' and '%s', op '%s' */
                        warning(124,
                            type_name(ltp), type_name(rtp), op_name(op));
                }
        }
}

static void
check_pointer_comparison(op_t op, const tnode_t *ln, const tnode_t *rn)
{
        type_t *ltp = ln->tn_type, *rtp = rn->tn_type;
        tspec_t lst = ltp->t_subt->t_tspec, rst = rtp->t_subt->t_tspec;

        if (lst == VOID || rst == VOID) {
                /* TODO: C99 behaves like C90 here. */
                if (!allow_trad && !allow_c99 &&
                    (lst == FUNC || rst == FUNC)) {
                        /* (void *)0 is already handled in typeok() */
                        const char *lsts, *rsts;
                        *(lst == FUNC ? &lsts : &rsts) = "function pointer";
                        *(lst == VOID ? &lsts : &rsts) = "'void *'";
                        /* C90 or later forbid comparison of %s with %s */
                        warning(274, lsts, rsts);
                }
                return;
        }

        if (!types_compatible(ltp->t_subt, rtp->t_subt, true, false, NULL)) {
                warn_incompatible_pointers(op, ltp, rtp);
                return;
        }

        if (lst == FUNC && rst == FUNC) {
                /* TODO: C99 behaves like C90 here, see C99 6.5.8p2. */
                if (!allow_trad && !allow_c99 && op != EQ && op != NE)
                        /* pointers to functions can only be compared ... */
                        warning(125);
        }
}

static bool
typeok_compare(op_t op,
               const tnode_t *ln, const type_t *ltp, tspec_t lt,
               const tnode_t *rn, const type_t *rtp, tspec_t rt)
{
        if (lt == PTR && rt == PTR) {
                check_pointer_comparison(op, ln, rn);
                return true;
        }

        if (lt != PTR && rt != PTR)
                return true;

        if (!is_integer(lt) && !is_integer(rt)) {
                warn_incompatible_types(op, ltp, lt, rtp, rt);
                return false;
        }

        const char *lx = lt == PTR ? "pointer" : "integer";
        const char *rx = rt == PTR ? "pointer" : "integer";
        /* invalid combination of %s '%s' and %s '%s', op '%s' */
        warning(123, lx, type_name(ltp), rx, type_name(rtp), op_name(op));
        return true;
}

static bool
typeok_quest(tspec_t lt, const tnode_t *rn)
{
        if (!is_scalar(lt)) {
                /* first operand of '?' must have scalar type */
                error(170);
                return false;
        }
        lint_assert(before_conversion(rn)->tn_op == COLON);
        return true;
}

static void
typeok_colon_pointer(const type_t *ltp, const type_t *rtp)
{
        type_t *lstp = ltp->t_subt;
        type_t *rstp = rtp->t_subt;
        tspec_t lst = lstp->t_tspec;
        tspec_t rst = rstp->t_tspec;

        if ((lst == VOID && rst == FUNC) || (lst == FUNC && rst == VOID)) {
                /* (void *)0 is handled in typeok_colon */
                /* TODO: C99 behaves like C90 here. */
                if (!allow_trad && !allow_c99)
                        /* conversion of %s to %s requires a cast, op %s */
                        warning(305, "function pointer", "'void *'",
                            op_name(COLON));
                return;
        }

        if (pointer_types_are_compatible(lstp, rstp, true))
                return;
        if (!types_compatible(lstp, rstp, true, false, NULL))
                warn_incompatible_pointers(COLON, ltp, rtp);
}

static bool
typeok_colon(const tnode_t *ln, const type_t *ltp, tspec_t lt,
             const tnode_t *rn, const type_t *rtp, tspec_t rt)
{

        if (is_arithmetic(lt) && is_arithmetic(rt))
                return true;
        if (lt == BOOL && rt == BOOL)
                return true;

        if (lt == STRUCT && rt == STRUCT && ltp->u.sou == rtp->u.sou)
                return true;
        if (lt == UNION && rt == UNION && ltp->u.sou == rtp->u.sou)
                return true;

        if (lt == PTR && is_null_pointer(rn))
                return true;
        if (rt == PTR && is_null_pointer(ln))
                return true;

        if ((lt == PTR && is_integer(rt)) || (is_integer(lt) && rt == PTR)) {
                const char *lx = lt == PTR ? "pointer" : "integer";
                const char *rx = rt == PTR ? "pointer" : "integer";
                /* invalid combination of %s '%s' and %s '%s', op '%s' */
                warning(123, lx, type_name(ltp),
                    rx, type_name(rtp), op_name(COLON));
                return true;
        }

        if (lt == VOID || rt == VOID) {
                if (lt != VOID || rt != VOID)
                        /* incompatible types '%s' and '%s' in conditional */
                        warning(126, expr_type_name(ln), expr_type_name(rn));
                return true;
        }

        if (lt == PTR && rt == PTR) {
                typeok_colon_pointer(ltp, rtp);
                return true;
        }

        /* incompatible types '%s' and '%s' in conditional */
        error(126, expr_type_name(ln), expr_type_name(rn));
        return false;
}

static bool
has_constant_member(const type_t *tp)
{
        lint_assert(is_struct_or_union(tp->t_tspec));

        for (sym_t *m = tp->u.sou->sou_first_member;
            m != NULL; m = m->s_next) {
                const type_t *mtp = m->s_type;
                if (mtp->t_const)
                        return true;
                if (is_struct_or_union(mtp->t_tspec) &&
                    has_constant_member(mtp))
                        return true;
        }
        return false;
}

static bool
typeok_assign(op_t op, const tnode_t *ln, const type_t *ltp, tspec_t lt)
{
        if (op == RETURN || op == INIT || op == FARG)
                return true;

        if (!ln->tn_lvalue) {
                if (ln->tn_op == CVT && ln->tn_cast &&
                    ln->u.ops.left->tn_op == LOAD)
                        /* a cast does not yield an lvalue */
                        error(163);
                /* %soperand of '%s' must be lvalue */
                error(114, "left ", op_name(op));
                return false;
        } else if (ltp->t_const
            || (is_struct_or_union(lt) && has_constant_member(ltp))) {
                if (allow_c90)
                        /* %soperand of '%s' must be modifiable lvalue */
                        warning(115, "left ", op_name(op));
        }
        return true;
}

static bool
typeok_scalar(op_t op, const mod_t *mp,
              const type_t *ltp, tspec_t lt,
              const type_t *rtp, tspec_t rt)
{
        if (mp->m_takes_bool && lt == BOOL && rt == BOOL)
                return true;
        if (mp->m_requires_integer) {
                if (!is_integer(lt) || (mp->m_binary && !is_integer(rt))) {
                        warn_incompatible_types(op, ltp, lt, rtp, rt);
                        return false;
                }
        } else if (mp->m_requires_integer_or_complex) {
                if ((!is_integer(lt) && !is_complex(lt)) ||
                    (mp->m_binary && (!is_integer(rt) && !is_complex(rt)))) {
                        warn_incompatible_types(op, ltp, lt, rtp, rt);
                        return false;
                }
        } else if (mp->m_requires_scalar) {
                if (!is_scalar(lt) || (mp->m_binary && !is_scalar(rt))) {
                        warn_incompatible_types(op, ltp, lt, rtp, rt);
                        return false;
                }
        } else if (mp->m_requires_arith) {
                if (!is_arithmetic(lt) ||
                    (mp->m_binary && !is_arithmetic(rt))) {
                        warn_incompatible_types(op, ltp, lt, rtp, rt);
                        return false;
                }
        }
        return true;
}

static void
check_assign_void_pointer(op_t op, int arg,
                          tspec_t lt, tspec_t lst,
                          tspec_t rt, tspec_t rst)
{

        if (!(lt == PTR && rt == PTR && (lst == VOID || rst == VOID)))
                return;
        /* two pointers, at least one pointer to void */

        /* TODO: C99 behaves like C90 here. */
        if (!(!allow_trad && !allow_c99 && (lst == FUNC || rst == FUNC)))
                return;
        /* comb. of ptr to func and ptr to void */

        const char *lts, *rts;
        *(lst == FUNC ? &lts : &rts) = "function pointer";
        *(lst == VOID ? &lts : &rts) = "'void *'";

        switch (op) {
        case INIT:
        case RETURN:
                /* conversion of %s to %s requires a cast */
                warning(303, rts, lts);
                break;
        case FARG:
                /* conversion of %s to %s requires a cast, arg #%d */
                warning(304, rts, lts, arg);
                break;
        default:
                /* conversion of %s to %s requires a cast, op %s */
                warning(305, rts, lts, op_name(op));
                break;
        }
}

static bool
is_direct_function_call(const tnode_t *tn, const char **out_name)
{

        if (tn->tn_op == CALL
            && tn->u.call->func->tn_op == ADDR
            && tn->u.call->func->u.ops.left->tn_op == NAME) {
                *out_name = tn->u.call->func->u.ops.left->u.sym->s_name;
                return true;
        }
        return false;
}

static bool
is_unconst_function(const char *name)
{

        return strcmp(name, "memchr") == 0 ||
            strcmp(name, "strchr") == 0 ||
            strcmp(name, "strpbrk") == 0 ||
            strcmp(name, "strrchr") == 0 ||
            strcmp(name, "strstr") == 0;
}

static bool
is_const_char_pointer(const tnode_t *tn)
{
        /*
         * For traditional reasons, C99 6.4.5p5 defines that string literals
         * have type 'char[]'.  They are often implicitly converted to 'char
         * *', for example when they are passed as function arguments.
         *
         * C99 6.4.5p6 further defines that modifying a string that is
         * constructed from a string literal invokes undefined behavior.
         *
         * Out of these reasons, string literals are treated as 'effectively
         * const' here.
         */
        if (tn->tn_op == CVT &&
            tn->u.ops.left->tn_op == ADDR &&
            tn->u.ops.left->u.ops.left->tn_op == STRING)
                return true;

        const type_t *tp = before_conversion(tn)->tn_type;
        return tp->t_tspec == PTR &&
            tp->t_subt->t_tspec == CHAR &&
            tp->t_subt->t_const;
}

static bool
is_const_pointer(const tnode_t *tn)
{
        const type_t *tp = before_conversion(tn)->tn_type;
        return tp->t_tspec == PTR && tp->t_subt->t_const;
}

static void
check_unconst_function(const type_t *lstp, const tnode_t *rn)
{
        const char *function_name;

        if (lstp->t_tspec == CHAR && !lstp->t_const &&
            is_direct_function_call(rn, &function_name) &&
            is_unconst_function(function_name) &&
            rn->u.call->args_len >= 1 &&
            is_const_char_pointer(rn->u.call->args[0])) {
                /* call to '%s' effectively discards 'const' from argument */
                warning(346, function_name);
        }

        if (!lstp->t_const &&
            is_direct_function_call(rn, &function_name) &&
            strcmp(function_name, "bsearch") == 0 &&
            rn->u.call->args_len >= 2 &&
            is_const_pointer(rn->u.call->args[1])) {
                /* call to '%s' effectively discards 'const' from argument */
                warning(346, function_name);
        }
}

static bool
check_assign_void_pointer_compat(op_t op, const function_call *call, int arg,
                                 tspec_t lt,
                                 const type_t *lstp, tspec_t lst,
                                 const tnode_t *rn,
                                 const type_t *rtp, tspec_t rt,
                                 const type_t *rstp, tspec_t rst)
{
        if (!(lt == PTR && rt == PTR && (lst == VOID || rst == VOID ||
                                         types_compatible(lstp, rstp,
                                             true, false, NULL))))
                return false;

        /* compatible pointer types (qualifiers ignored) */
        char qualifiers[32];
        snprintf(qualifiers, sizeof(qualifiers), "%s%s",
            !lstp->t_const && rstp->t_const ? " const" : "",
            !lstp->t_volatile && rstp->t_volatile ? " volatile" : "");
        if (allow_c90 && qualifiers[0] != '\0') {
                switch (op) {
                case INIT:
                case RETURN:
                        /* '%s' discards '%s' from '%s' */
                        warning(182, op_name(op),
                            qualifiers + 1, type_name(rtp));
                        break;
                case FARG:
                        /* passing '%s' as argument %d to '%s' discards '%s' */
                        warning(383, type_name(rtp), arg,
                            function_call_descr(call), qualifiers + 1);
                        break;
                default:
                        /* operator '%s' discards '%s' from '%s' */
                        warning(128, op_name(op),
                            qualifiers + 1, type_name(rtp));
                        break;
                }
        }

        if (allow_c90)
                check_unconst_function(lstp, rn);

        return true;
}

static bool
check_assign_pointer_integer(op_t op, int arg,
                             const type_t *ltp, tspec_t lt,
                             const type_t *rtp, tspec_t rt)
{

        if (!((lt == PTR && is_integer(rt)) || (is_integer(lt) && rt == PTR)))
                return false;

        const char *lx = lt == PTR ? "pointer" : "integer";
        const char *rx = rt == PTR ? "pointer" : "integer";

        switch (op) {
        case INIT:
        case RETURN:
                /* invalid combination of %s '%s' and %s '%s' for '%s' */
                warning(183,
                    lx, type_name(ltp), rx, type_name(rtp), op_name(op));
                break;
        case FARG:
                /* invalid combination of %s '%s' and %s '%s', arg #%d */
                warning(154,
                    lx, type_name(ltp), rx, type_name(rtp), arg);
                break;
        default:
                /* invalid combination of %s '%s' and %s '%s', op '%s' */
                warning(123,
                    lx, type_name(ltp), rx, type_name(rtp), op_name(op));
                break;
        }
        return true;
}

static bool
check_assign_pointer(op_t op, int arg,
                     const type_t *ltp, tspec_t lt,
                     const type_t *rtp, tspec_t rt)
{
        if (!(lt == PTR && rt == PTR))
                return false;

        if (op == FARG)
                /* converting '%s' to incompatible '%s' for ... */
                warning(153, type_name(rtp), type_name(ltp), arg);
        else
                warn_incompatible_pointers(op, ltp, rtp);
        return true;
}

static void
warn_assign(op_t op, int arg,
            const type_t *ltp, tspec_t lt,
            const type_t *rtp, tspec_t rt)
{
        switch (op) {
        case INIT:
                /* cannot initialize '%s' from '%s' */
                error(185, type_name(ltp), type_name(rtp));
                break;
        case RETURN:
                /* function has return type '%s' but returns '%s' */
                error(211, type_name(ltp), type_name(rtp));
                break;
        case FARG:
                /* passing '%s' to incompatible '%s', arg #%d */
                warning(155, type_name(rtp), type_name(ltp), arg);
                break;
        default:
                warn_incompatible_types(op, ltp, lt, rtp, rt);
                break;
        }
}

/*
 * Checks type compatibility for ASSIGN, INIT, FARG and RETURN
 * and prints warnings/errors if necessary.
 * Returns whether the types are (almost) compatible.
 */
static bool
check_assign_types_compatible(op_t op, const function_call *call, int arg,
                              const tnode_t *ln, const tnode_t *rn)
{
        tspec_t lt, rt, lst = NO_TSPEC, rst = NO_TSPEC;
        type_t *ltp, *rtp, *lstp = NULL, *rstp = NULL;

        if ((lt = (ltp = ln->tn_type)->t_tspec) == PTR)
                lst = (lstp = ltp->t_subt)->t_tspec;
        if ((rt = (rtp = rn->tn_type)->t_tspec) == PTR)
                rst = (rstp = rtp->t_subt)->t_tspec;

        if (lt == BOOL && is_scalar(rt))        /* C99 6.3.1.2 */
                return true;

        if (is_arithmetic(lt) && (is_arithmetic(rt) || rt == BOOL))
                return true;

        if (is_struct_or_union(lt) && is_struct_or_union(rt))
                return ltp->u.sou == rtp->u.sou;

        if (lt == PTR && is_null_pointer(rn)) {
                if (is_integer(rn->tn_type->t_tspec))
                        /* implicit conversion from integer 0 to pointer ... */
                        query_message(15, type_name(ltp));
                return true;
        }

        check_assign_void_pointer(op, arg, lt, lst, rt, rst);

        if (check_assign_void_pointer_compat(op, call, arg,
            lt, lstp, lst, rn, rtp, rt, rstp, rst))
                return true;

        if (check_assign_pointer_integer(op, arg, ltp, lt, rtp, rt))
                return true;

        if (check_assign_pointer(op, arg, ltp, lt, rtp, rt))
                return true;

        warn_assign(op, arg, ltp, lt, rtp, rt);
        return false;
}

static bool
has_side_effect(const tnode_t *tn) /* NOLINT(misc-no-recursion) */
{
        op_t op = tn->tn_op;

        if (modtab[op].m_has_side_effect)
                return true;

        if (op == CVT && tn->tn_type->t_tspec == VOID)
                return has_side_effect(tn->u.ops.left);

        if (op == LOGAND || op == LOGOR)
                return has_side_effect(tn->u.ops.right);

        if (op == QUEST)
                return has_side_effect(tn->u.ops.right);

        if (op == COLON || op == COMMA) {
                return has_side_effect(tn->u.ops.left) ||
                    has_side_effect(tn->u.ops.right);
        }

        return false;
}

static bool
is_void_cast(const tnode_t *tn)
{

        return tn->tn_op == CVT && tn->tn_cast &&
            tn->tn_type->t_tspec == VOID;
}

static bool
is_local_symbol(const tnode_t *tn)
{

        return tn->tn_op == LOAD &&
            tn->u.ops.left->tn_op == NAME &&
            tn->u.ops.left->u.sym->s_scl == AUTO;
}

static bool
is_int_constant_zero(const tnode_t *tn)
{

        return tn->tn_op == CON &&
            tn->tn_type->t_tspec == INT &&
            tn->u.value.u.integer == 0;
}

static void
check_null_effect(const tnode_t *tn)
{

        if (hflag &&
            !has_side_effect(tn) &&
            !(is_void_cast(tn) && is_local_symbol(tn->u.ops.left)) &&
            !(is_void_cast(tn) && is_int_constant_zero(tn->u.ops.left))) {
                /* expression has null effect */
                warning(129);
        }
}

/*
 * Check the types for specific operators and type combinations.
 *
 * At this point, the operands already conform to the type requirements of
 * the operator, such as being integer, floating or scalar.
 */
static bool
typeok_op(op_t op, const function_call *call, int arg,
          const tnode_t *ln, const type_t *ltp, tspec_t lt,
          const tnode_t *rn, const type_t *rtp, tspec_t rt)
{
        switch (op) {
        case ARROW:
                return typeok_arrow(lt);
        case POINT:
                return typeok_point(ln, ltp, lt);
        case INCBEF:
        case DECBEF:
        case INCAFT:
        case DECAFT:
                return typeok_incdec(op, ln, ltp);
        case INDIR:
                return typeok_indir(ltp, lt);
        case ADDR:
                return typeok_address(op, ln, ltp, lt);
        case PLUS:
                return typeok_plus(op, ltp, lt, rtp, rt);
        case MINUS:
                return typeok_minus(op, ltp, lt, rtp, rt);
        case SHL:
                typeok_shl(ln, lt, rn, rt);
                goto shift;
        case SHR:
                typeok_shr(ln, lt, rn, rt);
        shift:
                typeok_shift(ln, lt, rn, rt);
                break;
        case LT:
        case LE:
        case GT:
        case GE:
        compare:
                return typeok_compare(op, ln, ltp, lt, rn, rtp, rt);
        case EQ:
        case NE:
                if (is_typeok_eq(ln, lt, rn, rt))
                        break;
                goto compare;
        case QUEST:
                return typeok_quest(lt, rn);
        case COLON:
                return typeok_colon(ln, ltp, lt, rn, rtp, rt);
        case ASSIGN:
        case INIT:
        case FARG:
        case RETURN:
                if (!check_assign_types_compatible(op, call, arg, ln, rn))
                        return false;
                goto assign;
        case MULASS:
        case DIVASS:
        case MODASS:
                goto assign;
        case ADDASS:
        case SUBASS:
                if ((lt == PTR && !is_integer(rt)) || rt == PTR) {
                        warn_incompatible_types(op, ltp, lt, rtp, rt);
                        return false;
                }
                goto assign;
        case SHLASS:
                goto assign;
        case SHRASS:
                if (pflag && !is_uinteger(lt) &&
                    !(!allow_c90 && is_uinteger(rt))) {
                        /* bitwise '%s' on signed '%s' possibly nonportable */
                        warning(117, op_name(op), expr_type_name(rn));
                }
                goto assign;
        case ANDASS:
        case XORASS:
        case ORASS:
        assign:
                return typeok_assign(op, ln, ltp, lt);
        case COMMA:
                if (!modtab[ln->tn_op].m_has_side_effect)
                        check_null_effect(ln);
                break;
        default:
                break;
        }
        return true;
}

static void
check_bad_enum_operation(op_t op, const tnode_t *ln, const tnode_t *rn)
{

        if (!eflag)
                return;

        /* Allow enum in array indices. */
        if (op == PLUS &&
            ((ln->tn_type->t_is_enum && rn->tn_type->t_tspec == PTR) ||
             (rn->tn_type->t_is_enum && ln->tn_type->t_tspec == PTR))) {
                return;
        }

        /* dubious operation '%s' on enum */
        warning(241, op_name(op));
}

static void
check_enum_type_mismatch(op_t op, int arg, const tnode_t *ln, const tnode_t *rn)
{
        const mod_t *mp = &modtab[op];

        if (ln->tn_type->u.enumer != rn->tn_type->u.enumer) {
                switch (op) {
                case INIT:
                        /* enum type mismatch between '%s' and '%s' in ... */
                        warning(210,
                            type_name(ln->tn_type), type_name(rn->tn_type));
                        break;
                case FARG:
                        /* function expects '%s', passing '%s' for arg #%d */
                        warning(156,
                            type_name(ln->tn_type), type_name(rn->tn_type),
                            arg);
                        break;
                case RETURN:
                        /* function has return type '%s' but returns '%s' */
                        warning(211,
                            type_name(ln->tn_type), type_name(rn->tn_type));
                        break;
                default:
                        /* enum type mismatch: '%s' '%s' '%s' */
                        warning(130, expr_type_name(before_conversion(ln)),
                            op_name(op),
                            expr_type_name(before_conversion(rn)));
                        break;
                }
        } else if (Pflag && eflag && mp->m_comparison && op != EQ && op != NE)
                /* operator '%s' assumes that '%s' is ordered */
                warning(243, op_name(op), type_name(ln->tn_type));
}

static void
check_enum_int_mismatch(op_t op, int arg, const tnode_t *ln, const tnode_t *rn)
{

        if (!eflag)
                return;

        switch (op) {
        case INIT:
                /*
                 * Initialization with 0 is allowed. Otherwise, all implicit
                 * initializations would need to be warned upon as well.
                 */
                if (!rn->tn_type->t_is_enum && rn->tn_op == CON &&
                    is_integer(rn->tn_type->t_tspec) &&
                    rn->u.value.u.integer == 0) {
                        return;
                }
                /* initialization of '%s' with '%s' */
                warning(277, type_name(ln->tn_type), expr_type_name(rn));
                break;
        case FARG:
                /* combination of '%s' and '%s', arg #%d */
                warning(278,
                    type_name(ln->tn_type), expr_type_name(rn), arg);
                break;
        case RETURN:
                /* combination of '%s' and '%s' in return */
                warning(279, type_name(ln->tn_type), expr_type_name(rn));
                break;
        default:
                /* combination of '%s' and '%s', op '%s' */
                warning(242, type_name(ln->tn_type), expr_type_name(rn),
                    op_name(op));
                break;
        }
}

static void
typeok_enum(op_t op, const mod_t *mp, int arg,
            const tnode_t *ln, const type_t *ltp,
            const tnode_t *rn, const type_t *rtp)
{
        if (mp->m_bad_on_enum &&
            (ltp->t_is_enum || (mp->m_binary && rtp->t_is_enum))) {
                check_bad_enum_operation(op, ln, rn);
        } else if (mp->m_valid_on_enum &&
            (ltp->t_is_enum && rtp != NULL && rtp->t_is_enum)) {
                check_enum_type_mismatch(op, arg, ln, rn);
        } else if (mp->m_valid_on_enum &&
            (ltp->t_is_enum || (rtp != NULL && rtp->t_is_enum))) {
                check_enum_int_mismatch(op, arg, ln, rn);
        }
}

/* Perform most type checks. Return whether the types are ok. */
bool
typeok(op_t op, const function_call *call, int arg,
    const tnode_t *ln, const tnode_t *rn)
{

        const mod_t *mp = &modtab[op];

        type_t *ltp = ln->tn_type;
        tspec_t lt = ltp->t_tspec;

        type_t *rtp = mp->m_binary ? rn->tn_type : NULL;
        tspec_t rt = mp->m_binary ? rtp->t_tspec : NO_TSPEC;

        if (Tflag && !typeok_scalar_strict_bool(op, mp, arg, ln, rn))
                return false;
        if (!typeok_scalar(op, mp, ltp, lt, rtp, rt))
                return false;

        if (!typeok_op(op, call, arg, ln, ltp, lt, rn, rtp, rt))
                return false;

        typeok_enum(op, mp, arg, ln, ltp, rn, rtp);
        return true;
}

/* In traditional C, keep unsigned and promote FLOAT to DOUBLE. */
static tspec_t
promote_trad(tspec_t t)
{

        if (t == UCHAR || t == USHORT)
                return UINT;
        if (t == CHAR || t == SCHAR || t == SHORT)
                return INT;
        if (t == FLOAT)
                return DOUBLE;
        if (t == ENUM)
                return INT;
        return t;
}

/*
 * C99 6.3.1.1p2 requires for types with lower rank than int that "If an int
 * can represent all the values of the original type, the value is converted
 * to an int; otherwise it is converted to an unsigned int", and that "All
 * other types are unchanged by the integer promotions".
 */
static tspec_t
promote_c90(const tnode_t *tn, tspec_t t, bool farg)
{
        if (tn->tn_type->t_bitfield) {
                unsigned int width = tn->tn_type->t_bit_field_width;
                unsigned int int_width = size_in_bits(INT);
                // XXX: What about _Bool bit-fields, since C99?
                if (width < int_width)
                        return INT;
                if (width == int_width)
                        return is_uinteger(t) ? UINT : INT;
                return t;
        }

        if (t == CHAR || t == SCHAR)
                return INT;
        if (t == UCHAR)
                return size_in_bits(CHAR) < size_in_bits(INT) ? INT : UINT;
        if (t == SHORT)
                return INT;
        if (t == USHORT)
                return size_in_bits(SHORT) < size_in_bits(INT) ? INT : UINT;
        if (t == ENUM)
                return INT;
        if (farg && t == FLOAT)
                return DOUBLE;
        return t;
}

/*
 * Performs the "integer promotions" (C99 6.3.1.1p2), which convert small
 * integer types to either int or unsigned int.
 *
 * If allow_c90 is unset or the operand is a function argument with no type
 * information (no prototype or variable # of args), converts float to double.
 */
tnode_t *
promote(op_t op, bool farg, tnode_t *tn)
{

        const type_t *otp = tn->tn_type;
        tspec_t ot = otp->t_tspec;
        if (!is_arithmetic(ot))
                return tn;

        tspec_t nt = allow_c90 ? promote_c90(tn, ot, farg) : promote_trad(ot);
        if (nt == ot)
                return tn;

        type_t *ntp = expr_dup_type(gettyp(nt));
        ntp->t_tspec = nt;
        ntp->t_is_enum = otp->t_is_enum;
        if (ntp->t_is_enum)
                ntp->u.enumer = otp->u.enumer;
        return convert(op, 0, ntp, tn);
}

static void
check_lossy_floating_to_integer_conversion(
    op_t op, int arg, const type_t *tp, const tnode_t *tn)
{
        long double x = tn->u.value.u.floating;
        long double oob = powl(2.0L,
            width_in_bits(tp) - (is_uinteger(tp->t_tspec) ? 0 : 1));
        if (is_uinteger(tp->t_tspec)
            ? x >= 0.0L && x < oob && x == (uint64_t)x
            : x >= -oob && x < oob && x == (int64_t)x)
                return;
        if (op == FARG)
                /* lossy conversion of %Lg (%La) to '%s', arg #%d */
                warning(380, x, x, type_name(tp), arg);
        else
                /* lossy conversion of %Lg (%La) to '%s' */
                warning(381, x, x, type_name(tp));
}

static void
convert_integer_from_floating(
    op_t op, int arg, const type_t *tp, const tnode_t *tn)
{

        if (op == CVT)
                /* cast from floating point '%s' to integer '%s' */
                query_message(2, type_name(tn->tn_type), type_name(tp));
        else
                /* implicit conversion from floating point '%s' to ... */
                query_message(1, type_name(tn->tn_type), type_name(tp));
        if (tn->tn_op == CON && op != CVT)
                check_lossy_floating_to_integer_conversion(op, arg, tp, tn);
}

static bool
should_warn_about_prototype_conversion(tspec_t nt,
                                       tspec_t ot, const tnode_t *ptn)
{

        if (nt == ot)
                return false;

        if (nt == ENUM && ot == INT)
                return false;

        if (is_floating(nt) != is_floating(ot) ||
            portable_rank_cmp(nt, ot) != 0) {
                /* representation and/or width change */
                if (!is_integer(ot))
                        return true;
                /*
                 * XXX: Investigate whether this rule makes sense; see
                 * tests/usr.bin/xlint/lint1/platform_long.c.
                 */
                return portable_rank_cmp(ot, INT) > 0;
        }

        if (!hflag)
                return false;

        /*
         * If the types differ only in sign and the argument has the same
         * representation in both types, print no warning.
         */
        if (ptn->tn_op == CON && is_integer(nt) &&
            signed_type(nt) == signed_type(ot) &&
            !msb(ptn->u.value.u.integer, ot))
                return false;

        return true;
}

/*
 * Warn if a prototype causes a type conversion that is different from what
 * would happen to the same argument in the absence of a prototype.  This
 * check is intended for code that needs to stay compatible with pre-C90 C.
 *
 * Errors/warnings about invalid type combinations are already printed
 * in check_assign_types_compatible().
 */
static void
check_prototype_conversion(int arg, tspec_t nt, tspec_t ot, type_t *tp,
                           tnode_t *tn)
{

        if (!is_arithmetic(nt) || !is_arithmetic(ot))
                return;

        /*
         * If the type of the formal parameter is char/short, a warning would
         * be useless, because functions declared the old style can't expect
         * char/short arguments.
         */
        if (nt == CHAR || nt == SCHAR || nt == UCHAR ||
            nt == SHORT || nt == USHORT)
                return;

        tnode_t *ptn = promote(NOOP, true, tn);
        ot = ptn->tn_type->t_tspec;

        if (should_warn_about_prototype_conversion(nt, ot, ptn)) {
                /* argument %d is converted from '%s' to '%s' ... */
                warning(259, arg, expr_type_name(tn), type_name(tp));
        }
}

/*
 * When converting a large integer type to a small integer type, in some
 * cases the value of the actual expression is further restricted than the
 * type bounds, such as in (expr & 0xFF) or (expr % 100) or (expr >> 24).
 */
static bool
can_represent(const type_t *tp, const tnode_t *tn)
{
        uint64_t nmask = value_bits(width_in_bits(tp));
        if (!is_uinteger(tp->t_tspec))
                nmask >>= 1;

        integer_constraints c = ic_expr(tn);
        if ((~c.bclr & ~nmask) == 0)
                return true;

        integer_constraints tpc = ic_any(tp);
        if (is_uinteger(tp->t_tspec)
            ? tpc.umin <= c.umin && tpc.umax >= c.umax
            : tpc.smin <= c.smin && tpc.smax >= c.smax)
                return true;

        debug_enter();
        debug_step("type '%s' cannot represent:", type_name(tp));
        debug_node(tn);
        debug_leave();
        return false;
}

static bool
should_warn_about_integer_conversion(const type_t *ntp, tspec_t nt,
                                     const tnode_t *otn, tspec_t ot)
{

        // XXX: The portable_rank_cmp aims at portable mode, independent of the
        // current platform, while can_represent acts on the actual type sizes
        // from the current platform.  This mix is inconsistent, but anything
        // else would make the exact conditions too complicated to grasp.
        if (aflag > 0 && portable_rank_cmp(nt, ot) < 0) {
                if (ot == LONG || ot == ULONG
                    || ot == LLONG || ot == ULLONG
                    || ot == INT128 || ot == UINT128
                    || aflag > 1)
                        return !can_represent(ntp, otn);
        }
        return false;
}

static void
convert_integer_from_integer(op_t op, int arg, tspec_t nt, tspec_t ot,
                             type_t *tp, tnode_t *tn)
{

        if (tn->tn_op == CON)
                return;

        if (op == CVT)
                return;

        if (Pflag && pflag && aflag > 0 &&
            portable_rank_cmp(nt, ot) > 0 &&
            is_uinteger(nt) != is_uinteger(ot)) {
                if (op == FARG)
                        /* conversion to '%s' may sign-extend ... */
                        warning(297, type_name(tp), arg);
                else
                        /* conversion to '%s' may sign-extend ... */
                        warning(131, type_name(tp));
        }

        if (Pflag && portable_rank_cmp(nt, ot) > 0 &&
            (tn->tn_op == PLUS || tn->tn_op == MINUS || tn->tn_op == MULT ||
             tn->tn_op == SHL)) {
                /* suggest cast from '%s' to '%s' on op '%s' to ... */
                warning(324, type_name(gettyp(ot)), type_name(tp),
                    op_name(tn->tn_op));
        }

        if (should_warn_about_integer_conversion(tp, nt, tn, ot)) {
                if (op == FARG)
                        /* conversion from '%s' to '%s' may lose ... */
                        warning(298, expr_type_name(tn), type_name(tp), arg);
                else
                        /* conversion from '%s' to '%s' may lose accuracy */
                        warning(132, expr_type_name(tn), type_name(tp));
        }

        if (is_uinteger(nt) != is_uinteger(ot))
                /* implicit conversion changes sign from '%s' to '%s' */
                query_message(3, expr_type_name(tn), type_name(tp));
}

static void
convert_integer_from_pointer(op_t op, tspec_t nt, type_t *tp, tnode_t *tn)
{

        if (tn->tn_op == CON)
                return;
        if (op != CVT)
                return;         /* We already got an error. */
        if (portable_rank_cmp(nt, PTR) >= 0)
                return;

        if (pflag && size_in_bits(nt) >= size_in_bits(PTR)) {
                /* conversion of pointer to '%s' may lose bits */
                warning(134, type_name(tp));
        } else {
                /* conversion of pointer to '%s' loses bits */
                warning(133, type_name(tp));
        }
}

static bool
struct_starts_with(const type_t *struct_tp, const type_t *member_tp)
{

        return struct_tp->u.sou->sou_first_member != NULL &&
            types_compatible(struct_tp->u.sou->sou_first_member->s_type,
                member_tp, true, false, NULL);
}

static bool
is_byte_array(const type_t *tp)
{

        return tp->t_tspec == ARRAY &&
            (tp->t_subt->t_tspec == CHAR || tp->t_subt->t_tspec == UCHAR);
}

static bool
union_contains(const type_t *utp, const type_t *mtp)
{
        for (const sym_t *mem = utp->u.sou->sou_first_member;
            mem != NULL; mem = mem->s_next) {
                if (types_compatible(mem->s_type, mtp, true, false, NULL))
                        return true;
        }
        return false;
}

static bool
should_warn_about_pointer_cast(const type_t *nstp, tspec_t nst,
                               const type_t *ostp, tspec_t ost)
{

        while (nst == ARRAY)
                nstp = nstp->t_subt, nst = nstp->t_tspec;
        while (ost == ARRAY)
                ostp = ostp->t_subt, ost = ostp->t_tspec;

        if (nst == STRUCT && ost == STRUCT &&
            (struct_starts_with(nstp, ostp) ||
             struct_starts_with(ostp, nstp)))
                return false;

        if (is_incomplete(nstp) || is_incomplete(ostp))
                return false;

        if (nst == CHAR || nst == UCHAR)
                return false;   /* for the sake of traditional C code */
        if (ost == CHAR || ost == UCHAR)
                return false;   /* for the sake of traditional C code */

        /* Allow cast between pointers to sockaddr variants. */
        if (nst == STRUCT && ost == STRUCT) {
                const sym_t *nmem = nstp->u.sou->sou_first_member;
                const sym_t *omem = ostp->u.sou->sou_first_member;
                while (nmem != NULL && omem != NULL &&
                    types_compatible(nmem->s_type, omem->s_type,
                        true, false, NULL))
                        nmem = nmem->s_next, omem = omem->s_next;
                if (nmem != NULL && is_byte_array(nmem->s_type))
                        return false;
                if (omem != NULL && is_byte_array(omem->s_type))
                        return false;
                if (nmem == NULL && omem == NULL)
                        return false;
        }

        if (nst == UNION || ost == UNION) {
                const type_t *union_tp = nst == UNION ? nstp : ostp;
                const type_t *other_tp = nst == UNION ? ostp : nstp;
                if (union_contains(union_tp, other_tp))
                        return false;
        }

        if (is_struct_or_union(nst) && is_struct_or_union(ost))
                return nstp->u.sou != ostp->u.sou;

        enum rank_kind rk1 = type_properties(nst)->tt_rank_kind;
        enum rank_kind rk2 = type_properties(ost)->tt_rank_kind;
        if (rk1 != rk2 || rk1 == RK_NONE)
                return true;

        return portable_rank_cmp(nst, ost) != 0;
}

static void
convert_pointer_from_pointer(type_t *ntp, tnode_t *tn)
{
        const type_t *nstp = ntp->t_subt;
        const type_t *otp = tn->tn_type;
        const type_t *ostp = otp->t_subt;
        tspec_t nst = nstp->t_tspec;
        tspec_t ost = ostp->t_tspec;

        if (nst == VOID || ost == VOID) {
                /* TODO: C99 behaves like C90 here. */
                if (!allow_trad && !allow_c99 && (nst == FUNC || ost == FUNC)) {
                        const char *nts, *ots;
                        /* null pointers are already handled in convert() */
                        *(nst == FUNC ? &nts : &ots) = "function pointer";
                        *(nst == VOID ? &nts : &ots) = "'void *'";
                        /* conversion of %s to %s requires a cast */
                        warning(303, ots, nts);
                }
                return;
        }
        if (nst == FUNC && ost == FUNC)
                return;
        if (nst == FUNC || ost == FUNC) {
                /* converting '%s' to '%s' is questionable */
                warning(229, type_name(otp), type_name(ntp));
                return;
        }

        if (hflag && alignment(nstp) > alignment(ostp) &&
            !is_incomplete(ostp) && alignment(ostp) > 1 &&
            !(nst == UNION && union_contains(nstp, ostp))) {
                /* converting '%s' to '%s' increases alignment ... */
                warning(135, type_name(otp), type_name(ntp),
                    alignment(ostp), alignment(nstp));
        }

        if (cflag && should_warn_about_pointer_cast(nstp, nst, ostp, ost)) {
                /* pointer cast from '%s' to unrelated '%s' */
                warning(247, type_name(ostp), type_name(nstp));
        }
}

/*
 * Insert a conversion operator, which converts the type of the node
 * to another given type.
 *
 * Possible values for 'op':
 *      CVT     a cast-expression
 *      binary  integer promotion for one of the operands, or a usual
 *              arithmetic conversion
 *      binary  plain or compound assignments to bit-fields
 *      FARG    'arg' is the number of the parameter (used for warnings)
 *      NOOP    several other implicit conversions
 *      ...
 */
tnode_t *
convert(op_t op, int arg, type_t *tp, tnode_t *tn)
{
        tspec_t nt = tp->t_tspec;
        tspec_t ot = tn->tn_type->t_tspec;

        if (allow_trad && allow_c90 && op == FARG)
                check_prototype_conversion(arg, nt, ot, tp, tn);

        if (nt == BOOL) {
                /* No further checks. */

        } else if (is_integer(nt)) {
                if (ot == BOOL) {
                        /* No further checks. */
                } else if (is_integer(ot))
                        convert_integer_from_integer(op, arg, nt, ot, tp, tn);
                else if (is_floating(ot))
                        convert_integer_from_floating(op, arg, tp, tn);
                else if (ot == PTR)
                        convert_integer_from_pointer(op, nt, tp, tn);

        } else if (is_floating(nt)) {
                if (is_integer(ot) && op != CVT) {
                        /* implicit conversion from integer '%s' to ... */
                        query_message(19,
                            type_name(tn->tn_type), type_name(tp));
                }

        } else if (nt == PTR) {
                if (is_null_pointer(tn)) {
                        /* a null pointer may be assigned to any pointer. */
                } else if (ot == PTR && op == CVT)
                        convert_pointer_from_pointer(tp, tn);
        }

        tnode_t *ntn = expr_alloc_tnode();
        ntn->tn_op = CVT;
        ntn->tn_type = tp;
        ntn->tn_cast = op == CVT;
        ntn->tn_sys |= tn->tn_sys;
        ntn->u.ops.right = NULL;
        if (tn->tn_op != CON || nt == VOID) {
                ntn->u.ops.left = tn;
        } else {
                ntn->tn_op = CON;
                convert_constant(op, arg, ntn->tn_type, &ntn->u.value,
                    &tn->u.value);
        }

        return ntn;
}

static void
convert_constant_from_floating(op_t op, int arg, const type_t *ntp,
                               tspec_t nt, val_t *nv, val_t *ov)
{
        long double max = 0.0, min = 0.0;

        switch (nt) {
        case CHAR:
                max = TARG_CHAR_MAX;    min = TARG_CHAR_MIN;    break;
        case UCHAR:
                max = TARG_UCHAR_MAX;   min = 0;                break;
        case SCHAR:
                max = TARG_SCHAR_MAX;   min = TARG_SCHAR_MIN;   break;
        case SHORT:
                max = TARG_SHRT_MAX;    min = TARG_SHRT_MIN;    break;
        case USHORT:
                max = TARG_USHRT_MAX;   min = 0;                break;
        case ENUM:
        case INT:
                max = TARG_INT_MAX;     min = TARG_INT_MIN;     break;
        case UINT:
                max = TARG_UINT_MAX;    min = 0;                break;
        case LONG:
                max = TARG_LONG_MAX;    min = TARG_LONG_MIN;    break;
        case ULONG:
                max = TARG_ULONG_MAX;   min = 0;                break;
        case LLONG:
                max = LLONG_MAX;        min = LLONG_MIN;        break;
        case ULLONG:
                max = ULLONG_MAX;       min = 0;                break;
        case FLOAT:
        case FCOMPLEX:
                max = FLT_MAX;          min = -FLT_MAX;         break;
        case DOUBLE:
        case DCOMPLEX:
                max = DBL_MAX;          min = -DBL_MAX;         break;
        case LDOUBLE:
        case LCOMPLEX:
                /* LINTED 248; see floating_error_value. */
                max = LDBL_MAX;         min = -max;             break;
        default:
                lint_assert(false);
        }
        if (ov->u.floating > max || ov->u.floating < min) {
                lint_assert(nt != LDOUBLE);
                const char *ot_name = type_name(gettyp(ov->v_tspec));
                const char *nt_name = type_name(ntp);
                if (is_integer(nt))
                        goto after_warning;
                if (op == FARG)
                        /* conversion of '%s' to '%s' is out of range, ... */
                        warning(295, ot_name, nt_name, arg);
                else
                        /* conversion of '%s' to '%s' is out of range */
                        warning(119, ot_name, nt_name);
        after_warning:
                ov->u.floating = ov->u.floating > 0 ? max : min;
        }

        if (nt == FLOAT || nt == FCOMPLEX)
                nv->u.floating = (float)ov->u.floating;
        else if (nt == DOUBLE || nt == DCOMPLEX)
                nv->u.floating = (double)ov->u.floating;
        else if (nt == LDOUBLE || nt == LCOMPLEX)
                nv->u.floating = ov->u.floating;
        else
                nv->u.integer = (int64_t)ov->u.floating;
}

static bool
convert_constant_to_floating(tspec_t nt, val_t *nv,
                             tspec_t ot, const val_t *v)
{
        if (nt == FLOAT) {
                nv->u.floating = (ot == PTR || is_uinteger(ot)) ?
                    (float)(uint64_t)v->u.integer : (float)v->u.integer;
        } else if (nt == DOUBLE) {
                nv->u.floating = (ot == PTR || is_uinteger(ot)) ?
                    (double)(uint64_t)v->u.integer : (double)v->u.integer;
        } else if (nt == LDOUBLE) {
                nv->u.floating = (ot == PTR || is_uinteger(ot))
                    ? (long double)(uint64_t)v->u.integer
                    : (long double)v->u.integer;
        } else
                return false;
        return true;
}

static void
warn_constant_truncated(op_t op, const val_t *v)
{
        char buf[256];
        bool is_unsigned = is_uinteger(v->v_tspec);
        int64_t val = v->u.integer;
        unsigned long long abs_val = is_unsigned || val >= 0
            ? (unsigned long long)val
            : -(unsigned long long)val;
        const char *sign = is_unsigned || val >= 0 ? "" : "-";
        snprintf(buf, sizeof(buf), "%s%#llx", sign, abs_val);
        /* constant %s truncated by conversion, op '%s' */
        warning(306, buf, op_name(op));
}

static void
convert_constant_check_range_bitor(size_t nsz, size_t osz, const val_t *v,
                                   uint64_t xmask, op_t op)
{
        if (nsz < osz && (v->u.integer & xmask) != 0)
                warn_constant_truncated(op, v);
}

static void
convert_constant_check_range_bitand(size_t nsz, size_t osz,
                                    uint64_t xmask, const val_t *nv,
                                    tspec_t ot, const val_t *v,
                                    const type_t *tp, op_t op)
{
        if (nsz > osz &&
            (nv->u.integer & bit((unsigned int)(osz - 1))) != 0 &&
            (nv->u.integer & xmask) != xmask) {
                /* '%s' converts '%s' with its most significant bit being set to '%s' */
                warning(309,
                    op_name(op), type_name(gettyp(ot)), type_name(tp));
        } else if (nsz < osz &&
            (v->u.integer & xmask) != xmask &&
            (v->u.integer & xmask) != 0)
                warn_constant_truncated(op, v);
}

static void
convert_constant_check_range_signed(op_t op, int arg,
                                    const type_t *ntp, int64_t ov)
{
        if (op == ASSIGN)
                /* assignment of negative constant %lld to unsigned ... */
                warning(164, (long long)ov, type_name(ntp));
        else if (op == INIT)
                /* initialization of unsigned type '%s' with negative ... */
                warning(221, type_name(ntp), (long long)ov);
        else if (op == FARG)
                /* conversion of negative constant %lld to unsigned ... */
                warning(296, (long long)ov, type_name(ntp), arg);
        else if (modtab[op].m_comparison) {
                /* handled by check_integer_comparison() */
        } else
                /* conversion of negative constant %lld to unsigned ... */
                warning(222, (long long)ov, type_name(ntp));
}

/*
 * Loss of significant bit(s). All truncated bits of unsigned types or all
 * truncated bits plus the msb of the target for signed types are considered
 * to be significant bits. Loss of significant bits means that at least one
 * of the bits was set in an unsigned type or that at least one but not all
 * of the bits was set in a signed type. Loss of significant bits means that
 * it is not possible, also not with necessary casts, to convert back to the
 * original type. An example for a necessary cast is:
 *      char c; int     i; c = 128;
 *      i = c;                  ** yields -128 **
 *      i = (unsigned char)c;   ** yields 128 **
 */
static void
warn_constant_check_range_truncated(op_t op, int arg, const type_t *tp,
                                    tspec_t ot)
{
        if (op == ASSIGN && tp->t_bitfield)
                /* precision lost in bit-field assignment */
                warning(166);
        else if (op == ASSIGN)
                /* constant truncated by assignment */
                warning(165);
        else if (op == INIT && tp->t_bitfield)
                /* bit-field initializer does not fit */
                warning(180);
        else if (op == INIT)
                /* initializer does not fit */
                warning(178);
        else if (op == CASE)
                /* case label is converted from '%s' to '%s' */
                warning(196, tspec_name(ot), type_name(tp));
        else if (op == FARG)
                /* conversion of '%s' to '%s' is out of range, arg #%d */
                warning(295, type_name(gettyp(ot)), type_name(tp), arg);
        else
                /* conversion of '%s' to '%s' is out of range */
                warning(119, type_name(gettyp(ot)), type_name(tp));
}

static void
warn_constant_check_range_loss(op_t op, int arg, const type_t *tp,
                                  tspec_t ot)
{
        if (op == ASSIGN && tp->t_bitfield)
                /* precision lost in bit-field assignment */
                warning(166);
        else if (op == INIT && tp->t_bitfield)
                /* bit-field initializer out of range */
                warning(11);
        else if (op == CASE)
                /* case label is converted from '%s' to '%s' */
                warning(196, tspec_name(ot), type_name(tp));
        else if (op == FARG)
                /* conversion of '%s' to '%s' is out of range, arg #%d */
                warning(295, type_name(gettyp(ot)), type_name(tp), arg);
        else
                /* conversion of '%s' to '%s' is out of range */
                warning(119, type_name(gettyp(ot)), type_name(tp));
}

static void
convert_constant_check_range(tspec_t ot, const type_t *tp, tspec_t nt,
                             op_t op, int arg, const val_t *v, val_t *nv)
{
        unsigned int obitsz, nbitsz;
        uint64_t xmask, xmsk1;

        obitsz = size_in_bits(ot);
        nbitsz = tp->t_bitfield ? tp->t_bit_field_width : size_in_bits(nt);
        xmask = value_bits(nbitsz) ^ value_bits(obitsz);
        xmsk1 = value_bits(nbitsz) ^ value_bits(obitsz - 1);
        if (op == ORASS || op == BITOR || op == BITXOR) {
                convert_constant_check_range_bitor(
                    nbitsz, obitsz, v, xmask, op);
        } else if (op == ANDASS || op == BITAND) {
                convert_constant_check_range_bitand(
                    nbitsz, obitsz, xmask, nv, ot, v, tp, op);
        } else if (nt != PTR && is_uinteger(nt) &&
            ot != PTR && !is_uinteger(ot) && v->u.integer < 0)
                convert_constant_check_range_signed(op, arg, tp, v->u.integer);
        else if (nv->u.integer != v->u.integer && nbitsz <= obitsz &&
            (v->u.integer & xmask) != 0 &&
            (is_uinteger(ot) || (v->u.integer & xmsk1) != xmsk1))
                warn_constant_check_range_truncated(op, arg, tp, ot);
        else if (nv->u.integer != v->u.integer)
                warn_constant_check_range_loss(op, arg, tp, ot);
}

/* Converts a typed constant to a constant of another type. */
void
convert_constant(op_t op, int arg, const type_t *ntp, val_t *nv, val_t *ov)
{
        /*
         * TODO: make 'ov' const; the name of this function does not suggest
         *  that it modifies 'ov'.
         */
        tspec_t ot = ov->v_tspec;
        tspec_t nt = nv->v_tspec = ntp->t_tspec;
        bool range_check = false;

        if (nt == BOOL) {       /* C99 6.3.1.2 */
                nv->v_unsigned_since_c90 = false;
                nv->u.integer = is_nonzero_val(ov) ? 1 : 0;
                return;
        }

        if (ot == FLOAT || ot == DOUBLE || ot == LDOUBLE)
                convert_constant_from_floating(op, arg, ntp, nt, nv, ov);
        else if (!convert_constant_to_floating(nt, nv, ot, ov)) {
                range_check = true;     /* Check for lost precision. */
                nv->u.integer = ov->u.integer;
        }

        if (allow_trad && allow_c90 && ov->v_unsigned_since_c90 &&
            (is_floating(nt) || (
                (is_integer(nt) && !is_uinteger(nt) &&
                    portable_rank_cmp(nt, ot) > 0)))) {
                /* C90 treats constant as unsigned */
                warning(157);
                ov->v_unsigned_since_c90 = false;
        }

        if (is_integer(nt)) {
                unsigned int size = ntp->t_bitfield
                    ? ntp->t_bit_field_width : size_in_bits(nt);
                nv->u.integer = convert_integer(nv->u.integer, nt, size);
        }

        if (range_check && op != CVT)
                convert_constant_check_range(ot, ntp, nt, op, arg, ov, nv);
}

tnode_t *
build_sizeof(const type_t *tp)
{
        unsigned int size_in_bytes = type_size_in_bits(tp) / CHAR_SIZE;
        tnode_t *tn = build_integer_constant(SIZEOF_TSPEC, size_in_bytes);
        tn->tn_system_dependent = true;
        debug_step("build_sizeof '%s' = %u", type_name(tp), size_in_bytes);
        return tn;
}

tnode_t *
build_offsetof(const type_t *tp, designation dn)
{
        unsigned int offset_in_bits = 0;

        if (!is_struct_or_union(tp->t_tspec)) {
                /* unacceptable operand of '%s' */
                error(111, "offsetof");
                goto proceed;
        }
        for (size_t i = 0; i < dn.dn_len; i++) {
                const designator *dr = dn.dn_items + i;
                if (dr->dr_kind == DK_SUBSCRIPT) {
                        if (tp->t_tspec != ARRAY)
                                goto proceed;   /* silent error */
                        tp = tp->t_subt;
                        offset_in_bits += (unsigned)dr->dr_subscript
                            * type_size_in_bits(tp);
                } else {
                        if (!is_struct_or_union(tp->t_tspec))
                                goto proceed;   /* silent error */
                        const char *name = dr->dr_member->s_name;
                        sym_t *mem = find_member(tp->u.sou, name);
                        if (mem == NULL) {
                                /* type '%s' does not have member '%s' */
                                error(101, name, type_name(tp));
                                goto proceed;
                        }
                        tp = mem->s_type;
                        offset_in_bits += mem->u.s_member.sm_offset_in_bits;
                }
        }
        free(dn.dn_items);

proceed:;
        unsigned int offset_in_bytes = offset_in_bits / CHAR_SIZE;
        tnode_t *tn = build_integer_constant(SIZEOF_TSPEC, offset_in_bytes);
        tn->tn_system_dependent = true;
        return tn;
}

unsigned int
type_size_in_bits(const type_t *tp)
{

        unsigned int elem = 1;
        bool flex = false;
        lint_assert(tp != NULL);
        while (tp->t_tspec == ARRAY) {
                flex = true;    /* allow c99 flex arrays [] [0] */
                elem *= tp->u.dimension;
                tp = tp->t_subt;
        }
        if (elem == 0 && !flex) {
                /* cannot take size/alignment of incomplete type */
                error(143);
                elem = 1;
        }

        unsigned int elsz;
        switch (tp->t_tspec) {
        case VOID:
                /* cannot take size/alignment of void */
                error(146);
                elsz = 1;
                break;
        case FUNC:
                /* cannot take size/alignment of function type '%s' */
                error(144, type_name(tp));
                elsz = 1;
                break;
        case STRUCT:
        case UNION:
                if (is_incomplete(tp)) {
                        /* cannot take size/alignment of incomplete type */
                        error(143);
                        elsz = 1;
                } else
                        elsz = tp->u.sou->sou_size_in_bits;
                break;
        case ENUM:
                if (is_incomplete(tp)) {
                        /* cannot take size/alignment of incomplete type */
                        warning(143);
                }
                /* FALLTHROUGH */
        default:
                if (tp->t_bitfield)
                        /* cannot take size/alignment of bit-field */
                        error(145);
                elsz = size_in_bits(tp->t_tspec);
                lint_assert(elsz > 0);
                break;
        }

        return elem * elsz;
}

/* C11 6.5.3.4, GCC */
tnode_t *
build_alignof(const type_t *tp)
{
        if (tp->t_tspec == FUNC) {
                /* cannot take size/alignment of function type '%s' */
                error(144, type_name(tp));
                return NULL;
        }
        if (tp->t_tspec == VOID) {
                /* cannot take size/alignment of void */
                error(146);
                return NULL;
        }
        if (is_incomplete(tp)) {
                /* cannot take size/alignment of incomplete type */
                error(143);
                return NULL;
        }
        if (tp->t_bitfield) {
                /* cannot take size/alignment of bit-field */
                error(145);
                return NULL;
        }
        return build_integer_constant(SIZEOF_TSPEC, (int64_t)alignment(tp));
}

static tnode_t *
cast_to_union(tnode_t *otn, bool sys, type_t *ntp)
{

        if (!allow_gcc) {
                /* union cast is a GCC extension */
                error(328);
                return NULL;
        }

        for (const sym_t *m = ntp->u.sou->sou_first_member;
            m != NULL; m = m->s_next) {
                if (types_compatible(m->s_type, otn->tn_type,
                    false, false, NULL)) {
                        tnode_t *ntn = build_op(CVT, sys, ntp, otn, NULL);
                        ntn->tn_cast = true;
                        return ntn;
                }
        }

        /* type '%s' is not a member of '%s' */
        error(329, type_name(otn->tn_type), type_name(ntp));
        return NULL;
}

// In GCC mode, allow 'nullptr + offset' as a constant expression.
static tnode_t *
null_pointer_offset(tnode_t *tn)
{
        uint64_t off = 0;
        const tnode_t *n = tn;
        while ((n->tn_op == PLUS || n->tn_op == MINUS)
            && is_integer(n->u.ops.right->tn_type->t_tspec)) {
                off += (uint64_t)n->u.ops.right->u.value.u.integer;
                n = n->u.ops.left;
        }
        if (n->tn_type->t_tspec == PTR
            && n->tn_op == ADDR
            && n->u.ops.left->tn_op == INDIR
            && n->u.ops.left->u.ops.left->tn_op == CON
            && n->u.ops.left->u.ops.left->tn_type->t_tspec == PTR) {
                off += (uint64_t)n->u.ops.left->u.ops.left->u.value.u.integer;
                return build_integer_constant(SIZEOF_TSPEC, (int64_t)off);
        }
        return tn;
}

tnode_t *
cast(tnode_t *tn, bool sys, type_t *tp)
{

        if (tn == NULL)
                return NULL;

        tn = cconv(tn);

        lint_assert(tp != NULL);
        tspec_t nt = tp->t_tspec;
        tspec_t ot = tn->tn_type->t_tspec;

        if (nt == VOID) {
                /*
                 * C90 6.3.4, C99 6.5.4p2 and C11 6.5.4p2 allow any type to be
                 * cast to void.  The only other allowed casts are from a
                 * scalar type to a scalar type.
                 */
        } else if (nt == UNION)
                return cast_to_union(tn, sys, tp);
        else if (nt == STRUCT || nt == ARRAY || nt == FUNC) {
                /* Casting to a struct is an undocumented GCC extension. */
                if (!(allow_gcc && nt == STRUCT))
                        goto invalid_cast;
        } else if (is_struct_or_union(ot))
                goto invalid_cast;
        else if (ot == VOID) {
                /* improper cast of void expression */
                error(148);
                return NULL;
        } else if (is_integer(nt) && is_scalar(ot)) {
                tn = null_pointer_offset(tn);
        } else if (is_floating(nt) && is_arithmetic(ot)) {
                /* ok */
        } else if (nt == PTR && is_integer(ot)) {
                /* ok */
        } else if (nt == PTR && ot == PTR) {
                if (!tp->t_subt->t_const && tn->tn_type->t_subt->t_const) {
                        if (hflag)
                                /* cast discards 'const' from type '%s' */
                                warning(275, type_name(tn->tn_type));
                }
        } else
                goto invalid_cast;

        if (any_query_enabled
            && types_compatible(tp, tn->tn_type, false, false, NULL))
                /* no-op cast from '%s' to '%s' */
                query_message(6, expr_type_name(tn), type_name(tp));

        tn = convert(CVT, 0, tp, tn);
        tn->tn_cast = true;
        tn->tn_sys = sys;

        return tn;

invalid_cast:
        /* invalid cast from '%s' to '%s' */
        error(147, expr_type_name(tn), type_name(tp));
        return NULL;
}

void
add_function_argument(function_call *call, tnode_t *arg)
{
        /*
         * If there was a serious error in the expression for the argument,
         * create a dummy argument so the positions of the remaining arguments
         * will not change.
         */
        if (arg == NULL)
                arg = build_integer_constant(INT, 0);

        if (call->args_len >= call->args_cap) {
                call->args_cap += 8;
                tnode_t **new_args = expr_zero_alloc(
                    call->args_cap * sizeof(*call->args), "tnode*[]");
                if (call->args_len > 0)
                        memcpy(new_args, call->args,
                            call->args_len * sizeof(*call->args));
                call->args = new_args;
        }
        call->args[call->args_len++] = arg;
}

/*
 * Compare the type of an argument with the corresponding type of a
 * prototype parameter. If it is a valid combination, but both types
 * are not the same, insert a conversion to convert the argument into
 * the type of the parameter.
 */
static tnode_t *
convert_prototype_argument(const function_call *call, int arg,
    type_t *tp, tnode_t *tn)
{
        tnode_t *ln = xcalloc(1, sizeof(*ln));
        ln->tn_type = expr_unqualified_type(tp);
        ln->tn_lvalue = true;
        if (typeok(FARG, call, arg, ln, tn)) {
                bool dowarn;
                if (!types_compatible(tp, tn->tn_type,
                    true, false, (dowarn = false, &dowarn)) || dowarn)
                        tn = convert(FARG, arg, tp, tn);
        }
        free(ln);
        return tn;
}

static void
convert_function_arguments(const function_call *call)
{
        type_t *ftp = call->func->tn_type->t_subt;

        int npar = 0;
        for (const sym_t *p = ftp->u.params; p != NULL; p = p->s_next)
                npar++;

        int narg = (int)call->args_len;

        const sym_t *param = ftp->u.params;
        if (ftp->t_proto && npar != narg && !(ftp->t_vararg && npar < narg)) {
                /* argument mismatch: %d %s passed, %d expected */
                error(150, narg, narg != 1 ? "arguments" : "argument", npar);
                param = NULL;
        }

        for (int i = 0; i < narg; i++) {
                tnode_t *arg = call->args[i];

                tspec_t at = arg->tn_type->t_tspec;
                if (at == VOID) {
                        /* void expressions may not be arguments, arg #%d */
                        error(151, i + 1);
                        return;
                }
                if (is_struct_or_union(at) && is_incomplete(arg->tn_type)) {
                        /* argument cannot have unknown size, arg #%d */
                        error(152, i + 1);
                        return;
                }
                if (is_integer(at) &&
                    arg->tn_type->t_is_enum &&
                    is_incomplete(arg->tn_type)) {
                        /* argument cannot have unknown size, arg #%d */
                        warning(152, i + 1);
                }

                arg = cconv(arg);
                call->args[i] = arg;

                arg = param != NULL
                    ? convert_prototype_argument(call,
                        i + 1, param->s_type, arg)
                    : promote(NOOP, true, arg);
                call->args[i] = arg;

                if (param != NULL)
                        param = param->s_next;
        }
}

static bool
is_gcc_generic_atomic(const char *name)
{
        // https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html
        return strcmp(name, "__atomic_load_n") == 0
            || strcmp(name, "__atomic_exchange_n") == 0
            || strcmp(name, "__atomic_add_fetch") == 0
            || strcmp(name, "__atomic_sub_fetch") == 0
            || strcmp(name, "__atomic_and_fetch") == 0
            || strcmp(name, "__atomic_xor_fetch") == 0
            || strcmp(name, "__atomic_or_fetch") == 0
            || strcmp(name, "__atomic_nand_fetch") == 0
            || strcmp(name, "__atomic_fetch_add") == 0
            || strcmp(name, "__atomic_fetch_sub") == 0
            || strcmp(name, "__atomic_fetch_and") == 0
            || strcmp(name, "__atomic_fetch_xor") == 0
            || strcmp(name, "__atomic_fetch_or") == 0
            || strcmp(name, "__atomic_fetch_nand") == 0;
}

static type_t *
return_type(const function_call *call)
{
        const tnode_t *func = call->func;
        if (allow_gcc
            && func->tn_op == ADDR
            && func->u.ops.left->tn_op == NAME
            && is_gcc_generic_atomic(func->u.ops.left->u.sym->s_name)
            && call->args_len > 0
            && call->args[0]->tn_type->t_tspec == PTR)
                return call->args[0]->tn_type->t_subt;
        return func->tn_type->t_subt->t_subt;
}

tnode_t *
build_function_call(tnode_t *func, bool sys, function_call *call)
{

        if (func == NULL)
                return NULL;

        call->func = func;
        check_ctype_function_call(call);

        func = cconv(func);
        call->func = func;

        if (func->tn_type->t_tspec != PTR ||
            func->tn_type->t_subt->t_tspec != FUNC) {
                /* cannot call '%s', must be a function */
                error(149, expr_type_name(func));
                return NULL;
        }

        convert_function_arguments(call);

        tnode_t *ntn = expr_alloc_tnode();
        ntn->tn_op = CALL;
        ntn->tn_type = return_type(call);
        ntn->tn_sys = sys;
        ntn->u.call = call;
        return ntn;
}

/*
 * Return the value of an integral constant expression.
 * If the expression is not constant or its type is not an integer
 * type, an error message is printed.
 */
val_t *
integer_constant(tnode_t *tn, bool required)
{

        if (tn != NULL)
                tn = cconv(tn);
        if (tn != NULL)
                tn = promote(NOOP, false, tn);

        val_t *v = xcalloc(1, sizeof(*v));

        if (tn == NULL) {
                lint_assert(seen_error);
                debug_step("constant node is null; returning 1 instead");
                v->v_tspec = INT;
                v->u.integer = 1;
                return v;
        }

        v->v_tspec = tn->tn_type->t_tspec;

        if (tn->tn_op == CON) {
                lint_assert(tn->tn_type->t_tspec == tn->u.value.v_tspec);
                if (is_integer(tn->u.value.v_tspec)) {
                        v->v_unsigned_since_c90 =
                            tn->u.value.v_unsigned_since_c90;
                        v->u.integer = tn->u.value.u.integer;
                        return v;
                }
                v->u.integer = (int64_t)tn->u.value.u.floating;
        } else
                v->u.integer = 1;

        if (required)
                /* integral constant expression expected */
                error(55);
        else
                /* variable array dimension is a C99/GCC extension */
                c99ism(318);

        if (!is_integer(v->v_tspec))
                v->v_tspec = INT;

        return v;
}

/*
 * Perform some tests on expressions which can't be done in build_binary()
 * and functions called by build_binary(). These tests must be done here
 * because we need some information about the context in which the operations
 * are performed.
 * After all tests are performed, if free_expr is true, expr() frees the
 * memory for the expression.
 */
void
expr(tnode_t *tn, bool used, bool cond, bool free_expr, bool is_do_while,
    const char *stmt_kind)
{

        if (tn == NULL) {       /* in case of errors */
                expr_free_all();
                return;
        }

        /* expr() is also called in global initializations */
        if (dcs->d_kind != DLK_EXTERN && !is_do_while)
                check_statement_reachable(stmt_kind);

        check_expr_misc(tn, used, cond, !cond, false, false, false);
        if (tn->tn_op == ASSIGN && !tn->tn_parenthesized) {
                if (hflag && cond)
                        /* assignment in conditional context */
                        warning(159);
        }
        if (!modtab[tn->tn_op].m_has_side_effect) {
                /*
                 * for left operands of COMMA this warning is already printed
                 */
                if (tn->tn_op != COMMA && !used && !cond)
                        check_null_effect(tn);
        }
        debug_node(tn);

        if (free_expr)
                expr_free_all();
}

/* If the expression has the form '*(arr + idx)', check the array index. */
static void
check_array_index(const tnode_t *indir, bool taking_address)
{
        const tnode_t *plus, *arr, *idx;

        if (indir->tn_op == INDIR
            && (plus = indir->u.ops.left, plus->tn_op == PLUS)
            && plus->u.ops.left->tn_op == ADDR
            && (arr = plus->u.ops.left->u.ops.left, true)
            && (arr->tn_op == STRING || arr->tn_op == NAME)
            && arr->tn_type->t_tspec == ARRAY
            && (idx = plus->u.ops.right, idx->tn_op == CON)
            && (!is_incomplete(arr->tn_type) || idx->u.value.u.integer < 0))
                goto proceed;
        return;

proceed:;
        int elsz = length_in_bits(arr->tn_type->t_subt, NULL);
        if (elsz == 0)
                return;
        elsz /= CHAR_SIZE;

        /* Change the unit of the index from bytes to element size. */
        int64_t con = is_uinteger(idx->tn_type->t_tspec)
            ? (int64_t)((uint64_t)idx->u.value.u.integer / elsz)
            : idx->u.value.u.integer / elsz;

        int dim = arr->tn_type->u.dimension + (taking_address ? 1 : 0);

        if (!is_uinteger(idx->tn_type->t_tspec) && con < 0)
                /* array subscript %jd cannot be negative */
                warning(167, (intmax_t)con);
        else if (dim > 0 && (uint64_t)con >= (uint64_t)dim)
                /* array subscript %ju cannot be > %d */
                warning(168, (uintmax_t)con, dim - 1);
}

static void
check_expr_addr(const tnode_t *ln, bool szof, bool fcall)
{
        /* XXX: Taking warn_about_unreachable into account here feels wrong. */
        if (ln->tn_op == NAME && (reached || !warn_about_unreachable)) {
                if (!szof)
                        mark_as_set(ln->u.sym);
                mark_as_used(ln->u.sym, fcall, szof);
        }
        check_array_index(ln, true);
}

/*
 * If there is an asm statement in one of the compound statements around,
 * there may be other side effects, so don't warn.
 */
static bool
is_asm_around(void)
{
        for (decl_level *dl = dcs; dl != NULL; dl = dl->d_enclosing)
                if (dl->d_asm)
                        return true;
        return false;
}

static void
check_expr_side_effect(const tnode_t *ln, bool szof)
{

        /* XXX: Taking warn_about_unreachable into account here feels wrong. */
        if (ln->tn_op == NAME && (reached || !warn_about_unreachable)) {
                scl_t sc = ln->u.sym->s_scl;
                if (sc != EXTERN && sc != STATIC &&
                    !ln->u.sym->s_set && !szof && !is_asm_around()) {
                        /* '%s' may be used before set */
                        warning(158, ln->u.sym->s_name);
                        mark_as_set(ln->u.sym);
                }
                mark_as_used(ln->u.sym, false, false);
        }
}

static void
check_expr_assign(const tnode_t *ln, bool szof)
{
        /* XXX: Taking warn_about_unreachable into account here feels wrong. */
        if (ln->tn_op == NAME && !szof && (reached || !warn_about_unreachable)) {
                mark_as_set(ln->u.sym);
                if (ln->u.sym->s_scl == EXTERN)
                        outusg(ln->u.sym);
        }
        check_array_index(ln, false);
}

static void
check_expr_call(const tnode_t *tn, const tnode_t *ln,
                bool szof, bool vctx, bool cond, bool retval_discarded)
{
        lint_assert(ln->tn_op == ADDR);
        lint_assert(ln->u.ops.left->tn_op == NAME);
        if (!szof && !is_compiler_builtin(ln->u.ops.left->u.sym->s_name))
                outcall(tn, vctx || cond, retval_discarded);

        const function_call *call = tn->u.call;
        if (call->args_len == 4 || call->args_len == 5)
                check_snprintb(call);
}

static void
check_expr_op(op_t op, const tnode_t *ln, bool szof, bool fcall, bool eqwarn)
{
        switch (op) {
        case ADDR:
                check_expr_addr(ln, szof, fcall);
                break;
        case LOAD:
                check_array_index(ln, false);
                /* FALLTHROUGH */
        case INCBEF:
        case DECBEF:
        case INCAFT:
        case DECAFT:
        case ADDASS:
        case SUBASS:
        case MULASS:
        case DIVASS:
        case MODASS:
        case ANDASS:
        case ORASS:
        case XORASS:
        case SHLASS:
        case SHRASS:
        case REAL:
        case IMAG:
                check_expr_side_effect(ln, szof);
                break;
        case ASSIGN:
                check_expr_assign(ln, szof);
                break;
        case EQ:
                if (hflag && eqwarn)
                        /* operator '==' found where '=' was expected */
                        warning(160);
                break;
        default:
                break;
        }
}

/*
 *      vctx                    ???
 *      cond                    whether the expression is a condition that
 *                              will be compared with 0
 *      eqwarn                  whether the operator '==' might be a
 *                              misspelled '='
 *      fcall                   whether the expression is a function call
 *      retval_discarded        whether the return value of a function call
 *                              is discarded; such calls will be analyzed by
 *                              lint2 in messages 4, 8 and 9
 *      szof                    whether the expression is part of a sizeof
 *                              expression, which means that its value is
 *                              discarded since only the type is relevant
 */
void
check_expr_misc(const tnode_t *tn, bool vctx, bool cond,
                bool eqwarn, bool fcall, bool retval_discarded, bool szof)
{

        if (tn == NULL)
                return;
        op_t op = tn->tn_op;
        if (op == NAME || op == CON || op == STRING)
                return;
        bool is_direct = op == CALL
            && tn->u.call->func->tn_op == ADDR
            && tn->u.call->func->u.ops.left->tn_op == NAME;
        if (op == CALL) {
                const function_call *call = tn->u.call;
                if (is_direct)
                        check_expr_call(tn, call->func,
                            szof, vctx, cond, retval_discarded);
                bool discard = op == CVT && tn->tn_type->t_tspec == VOID;
                check_expr_misc(call->func, false, false, false, is_direct,
                    discard, szof);
                for (size_t i = 0, n = call->args_len; i < n; i++)
                        check_expr_misc(call->args[i],
                            true, false, false, false, false, szof);
                return;
        }

        lint_assert(has_operands(tn));
        tnode_t *ln = tn->u.ops.left;
        tnode_t *rn = tn->u.ops.right;
        check_expr_op(op, ln, szof, fcall, eqwarn);

        const mod_t *mp = &modtab[op];
        bool cvctx = mp->m_value_context;
        bool ccond = mp->m_compares_with_zero;
        bool eq = mp->m_warn_if_operand_eq &&
            !ln->tn_parenthesized &&
            rn != NULL && !rn->tn_parenthesized;

        /*
         * Values of operands of ':' are not used if the type of at least
         * one of the operands (for GCC compatibility) is 'void'.
         *
         * XXX test/value context of QUEST should probably be used as
         * context for both operands of COLON.
         */
        if (op == COLON && tn->tn_type->t_tspec == VOID)
                cvctx = ccond = false;
        bool discard = op == CVT && tn->tn_type->t_tspec == VOID;
        check_expr_misc(ln, cvctx, ccond, eq, is_direct, discard, szof);

        switch (op) {
        case LOGAND:
        case LOGOR:
                check_expr_misc(rn, false, true, eq, false, false, szof);
                break;
        case COLON:
                check_expr_misc(rn, cvctx, ccond, eq, false, false, szof);
                break;
        case COMMA:
                check_expr_misc(rn, vctx, cond, false, false, false, szof);
                break;
        default:
                if (mp->m_binary)
                        check_expr_misc(rn, true, false, eq, false, false,
                            szof);
                break;
        }
}

/*
 * Return whether the expression can be used for static initialization.
 *
 * Constant initialization expressions must be constant or an address
 * of a static object with an optional offset. In the first case,
 * the result is returned in *offsp. In the second case, the static
 * object is returned in *symp and the offset in *offsp.
 *
 * The expression can consist of PLUS, MINUS, ADDR, NAME, STRING and
 * CON. Type conversions are allowed if they do not change binary
 * representation (including width).
 *
 * C99 6.6 "Constant expressions"
 * C99 6.7.8p4 restricts initializers for static storage duration
 */
bool
constant_addr(const tnode_t *tn, const sym_t **symp, ptrdiff_t *offsp)
{
        const sym_t *sym;
        ptrdiff_t offs1, offs2;
        tspec_t t, ot;

        switch (tn->tn_op) {
        case MINUS:
                if (tn->u.ops.right->tn_op == CVT)
                        return constant_addr(tn->u.ops.right, symp, offsp);
                if (tn->u.ops.right->tn_op != CON)
                        return false;
                /* FALLTHROUGH */
        case PLUS:
                offs1 = offs2 = 0;
                if (tn->u.ops.left->tn_op == CON) {
                        offs1 = (ptrdiff_t)tn->u.ops.left->u.value.u.integer;
                        if (!constant_addr(tn->u.ops.right, &sym, &offs2))
                                return false;
                } else if (tn->u.ops.right->tn_op == CON) {
                        offs2 = (ptrdiff_t)tn->u.ops.right->u.value.u.integer;
                        if (tn->tn_op == MINUS)
                                offs2 = -offs2;
                        if (!constant_addr(tn->u.ops.left, &sym, &offs1))
                                return false;
                } else {
                        return false;
                }
                *symp = sym;
                *offsp = offs1 + offs2;
                return true;
        case ADDR:
                if (tn->u.ops.left->tn_op == NAME) {
                        *symp = tn->u.ops.left->u.sym;
                        *offsp = 0;
                        return true;
                }
                *symp = NULL;
                *offsp = 0;
                return true;
        case CVT:
                t = tn->tn_type->t_tspec;
                ot = tn->u.ops.left->tn_type->t_tspec;
                if ((!is_integer(t) && t != PTR) ||
                    (!is_integer(ot) && ot != PTR)) {
                        return false;
                }
#if 0
                /*-
                 * consider:
                 *      struct foo {
                 *              unsigned char a;
                 *      } f = {
                 *              (unsigned char)(unsigned long)
                 *                  (&(((struct foo *)0)->a))
                 *      };
                 * since psize(unsigned long) != psize(unsigned char),
                 * this fails.
                 */
                else if (psize(t) != psize(ot))
                        return -1;
#endif
                return constant_addr(tn->u.ops.left, symp, offsp);
        default:
                return false;
        }
}

/* Append s2 to s1, then free s2. */
buffer *
cat_strings(buffer *s1, buffer *s2)
{

        if ((s1->data != NULL) != (s2->data != NULL)) {
                /* cannot concatenate wide and regular string literals */
                error(292);
                return s1;
        }

        if (s1->data != NULL) {
                while (s1->len + s2->len + 1 > s1->cap)
                        s1->cap *= 2;
                s1->data = xrealloc(s1->data, s1->cap);
                memcpy(s1->data + s1->len, s2->data, s2->len + 1);
                free(s2->data);
        }
        s1->len += s2->len;
        free(s2);

        return s1;
}


typedef struct stmt_expr {
        memory_pool se_mem;
        sym_t *se_sym;
        struct stmt_expr *se_enclosing;
} stmt_expr;

static stmt_expr *stmt_exprs;

void
begin_statement_expr(void)
{
        debug_enter();

        stmt_expr *se = xmalloc(sizeof(*se));
        se->se_mem = expr_save_memory();
        se->se_sym = NULL;
        se->se_enclosing = stmt_exprs;
        stmt_exprs = se;
}

void
do_statement_expr(tnode_t *tn)
{
        block_level--;
        mem_block_level--;
        stmt_exprs->se_sym = tn != NULL
            ? mktempsym(block_dup_type(tn->tn_type))
            : NULL;             /* after a syntax error */
        mem_block_level++;
        block_level++;
        /* '({ ... })' is a GCC extension */
        gnuism(320);
}

tnode_t *
end_statement_expr(void)
{
        tnode_t *tn;

        stmt_expr *se = stmt_exprs;
        if (se->se_sym == NULL) {
                tn = NULL;      /* after a syntax error */
                goto end;
        }

        tn = build_name(se->se_sym, false);
        (void)expr_save_memory();       /* leak */
        expr_restore_memory(se->se_mem);
        stmt_exprs = se->se_enclosing;
        free(se);

end:
        debug_leave();
        return tn;
}

bool
in_statement_expr(void)
{
        return stmt_exprs != NULL;
}