/* $OpenBSD: gnum4.c,v 1.55 2025/11/05 17:10:45 tb Exp $ */

/*
 * Copyright (c) 1999-2022 Marc Espie <espie@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * functions needed to support gnu-m4 extensions, including a fake freezing
 */

#include <sys/types.h>
#include <sys/wait.h>
#include <ctype.h>
#include <err.h>
#include <paths.h>
#include <regex.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <limits.h>
#include "mdef.h"
#include "stdd.h"
#include "extern.h"


int mimic_gnu = 0;

/*
 * Support for include path search
 * First search in the current directory.
 * If not found, and the path is not absolute, include path kicks in.
 * First, -I options, in the order found on the command line.
 * Then M4PATH env variable
 */

struct path_entry {
        char *name;
        struct path_entry *next;
} *first, *last;

static struct path_entry *new_path_entry(const char *);
static void ensure_m4path(void);
static struct input_file *dopath(struct input_file *, const char *);

static struct path_entry *
new_path_entry(const char *dirname)
{
        struct path_entry *n;

        n = malloc(sizeof(struct path_entry));
        if (!n)
                errx(1, "out of memory");
        n->name = xstrdup(dirname);
        n->next = 0;
        return n;
}

void
addtoincludepath(const char *dirname)
{
        struct path_entry *n;

        n = new_path_entry(dirname);

        if (last) {
                last->next = n;
                last = n;
        }
        else
                last = first = n;
}

static void
ensure_m4path(void)
{
        static int envpathdone = 0;
        char *envpath;
        char *sweep;
        char *path;

        if (envpathdone)
                return;
        envpathdone = TRUE;
        envpath = getenv("M4PATH");
        if (!envpath)
                return;
        /* for portability: getenv result is read-only */
        envpath = xstrdup(envpath);
        for (sweep = envpath;
            (path = strsep(&sweep, ":")) != NULL;)
            addtoincludepath(path);
        free(envpath);
}

static
struct input_file *
dopath(struct input_file *i, const char *filename)
{
        char path[PATH_MAX];
        struct path_entry *pe;
        FILE *f;

        for (pe = first; pe; pe = pe->next) {
                snprintf(path, sizeof(path), "%s/%s", pe->name, filename);
                if ((f = fopen(path, "r")) != 0) {
                        set_input(i, f, path);
                        return i;
                }
        }
        return NULL;
}

struct input_file *
fopen_trypath(struct input_file *i, const char *filename)
{
        FILE *f;

        f = fopen(filename, "r");
        if (f != NULL) {
                set_input(i, f, filename);
                return i;
        }
        if (filename[0] == '/')
                return NULL;

        ensure_m4path();

        return dopath(i, filename);
}

void
doindir(const char *argv[], int argc)
{
        ndptr n;
        struct macro_definition *p;

        n = lookup(argv[2]);
        if (n == NULL || (p = macro_getdef(n)) == NULL)
                m4errx(1, "indir: undefined macro %s.", argv[2]);
        argv[1] = p->defn;

        eval(argv+1, argc-1, p->type, is_traced(n));
}

void
dobuiltin(const char *argv[], int argc)
{
        ndptr p;

        argv[1] = NULL;
        p = macro_getbuiltin(argv[2]);
        if (p != NULL)
                eval(argv+1, argc-1, macro_builtin_type(p), is_traced(p));
        else
                m4errx(1, "unknown builtin %s.", argv[2]);
}


/* We need some temporary buffer space, as pb pushes BACK and substitution
 * proceeds forward... */
static char *buffer;
static size_t bufsize = 0;
static size_t current = 0;

static void addchars(const char *, size_t);
static void addchar(int);
static char *twiddle(const char *);
static char *getstring(void);
static void exit_regerror(int, regex_t *, const char *);
static void do_subst(const char *, regex_t *, const char *, const char *, 
    regmatch_t *);
static void do_regexpindex(const char *, regex_t *, const char *, regmatch_t *);
static void do_regexp(const char *, regex_t *, const char *, const char *, 
    regmatch_t *);
static void add_sub(int, const char *, regex_t *, regmatch_t *);
static void add_replace(const char *, regex_t *, const char *, regmatch_t *);
#define addconstantstring(s) addchars((s), sizeof(s)-1)

static void
addchars(const char *c, size_t n)
{
        if (n == 0)
                return;
        while (current + n > bufsize) {
                if (bufsize == 0)
                        bufsize = 1024;
                else if (bufsize <= SIZE_MAX/2) {
                        bufsize *= 2;
                } else {
                        errx(1, "size overflow");
                }
                buffer = xrealloc(buffer, bufsize, NULL);
        }
        memcpy(buffer+current, c, n);
        current += n;
}

static void
addchar(int c)
{
        if (current +1 > bufsize) {
                if (bufsize == 0)
                        bufsize = 1024;
                else
                        bufsize *= 2;
                buffer = xrealloc(buffer, bufsize, NULL);
        }
        buffer[current++] = c;
}

static char *
getstring(void)
{
        addchar('\0');
        current = 0;
        return buffer;
}


static void
exit_regerror(int er, regex_t *re, const char *source)
{
        size_t  errlen;
        char    *errbuf;

        errlen = regerror(er, re, NULL, 0);
        errbuf = xalloc(errlen,
            "malloc in regerror: %lu", (unsigned long)errlen);
        regerror(er, re, errbuf, errlen);
        m4errx(1, "regular expression error in %s: %s.", source, errbuf);
}

/* warnx() plus check to see if we need to change exit code or exit.
 * -E flag functionality.
 */
void
m4_warnx(const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        vwarnx(fmt, ap);
        va_end(ap);

        if (fatal_warns)
                exit(1);
        if (error_warns)
                exit_code = 1;
}

static void
add_sub(int n, const char *string, regex_t *re, regmatch_t *pm)
{
        if (n > re->re_nsub)
                m4_warnx("No subexpression %d", n);
        /* Subexpressions that did not match are
         * not an error.  */
        else if (pm[n].rm_so != -1 &&
            pm[n].rm_eo != -1) {
                addchars(string + pm[n].rm_so,
                        pm[n].rm_eo - pm[n].rm_so);
        }
}

/* Add replacement string to the output buffer, recognizing special
 * constructs and replacing them with substrings of the original string.
 */
static void
add_replace(const char *string, regex_t *re, const char *replace, regmatch_t *pm)
{
        const char *p;

        for (p = replace; *p != '\0'; p++) {
                if (*p == '&' && !mimic_gnu) {
                        add_sub(0, string, re, pm);
                        continue;
                }
                if (*p == '\\') {
                        if (p[1] == '\\') {
                                addchar(p[1]);
                                p++;
                                continue;
                        }
                        if (p[1] == '&') {
                                if (mimic_gnu)
                                        add_sub(0, string, re, pm);
                                else
                                        addchar(p[1]);
                                p++;
                                continue;
                        }
                        if (isdigit((unsigned char)p[1])) {
                                add_sub(*(++p) - '0', string, re, pm);
                                continue;
                        }
                }
                addchar(*p);
        }
}

static void
do_subst(const char *string, regex_t *re, const char *source, 
    const char *replace, regmatch_t *pm)
{
        int error;
        int flags = 0;
        const char *last_match = NULL;

        while ((error = regexec(re, string, re->re_nsub+1, pm, flags)) == 0) {
                if (pm[0].rm_eo != 0) {
                        if (string[pm[0].rm_eo-1] == '\n')
                                flags = 0;
                        else
                                flags = REG_NOTBOL;
                }

                /* NULL length matches are special... We use the `vi-mode'
                 * rule: don't allow a NULL-match at the last match
                 * position.
                 */
                if (pm[0].rm_so == pm[0].rm_eo &&
                    string + pm[0].rm_so == last_match) {
                        if (*string == '\0')
                                return;
                        addchar(*string);
                        if (*string++ == '\n')
                                flags = 0;
                        else
                                flags = REG_NOTBOL;
                        continue;
                }
                last_match = string + pm[0].rm_so;
                addchars(string, pm[0].rm_so);
                add_replace(string, re, replace, pm);
                string += pm[0].rm_eo;
        }
        if (error != REG_NOMATCH)
                exit_regerror(error, re, source);
        pbstr(string);
}

static void
do_regexp(const char *string, regex_t *re, const char *source, 
    const char *replace, regmatch_t *pm)
{
        int error;

        switch(error = regexec(re, string, re->re_nsub+1, pm, 0)) {
        case 0:
                add_replace(string, re, replace, pm);
                pbstr(getstring());
                break;
        case REG_NOMATCH:
                break;
        default:
                exit_regerror(error, re, source);
        }
}

static void
do_regexpindex(const char *string, regex_t *re, const char *source, 
    regmatch_t *pm)
{
        int error;

        switch(error = regexec(re, string, re->re_nsub+1, pm, 0)) {
        case 0:
                pbunsigned(pm[0].rm_so);
                break;
        case REG_NOMATCH:
                pbnum(-1);
                break;
        default:
                exit_regerror(error, re, source);
        }
}

/* In Gnu m4 mode, parentheses for backmatch don't work like POSIX 1003.2
 * says. So we twiddle with the regexp before passing it to regcomp.
 */
static char *
twiddle(const char *p)
{
        /* + at start of regexp is a normal character for Gnu m4 */
        if (*p == '^') {
                addchar(*p);
                p++;
        }
        if (*p == '+') {
                addchar('\\');
        }
        /* This could use strcspn for speed... */
        while (*p != '\0') {
                if (*p == '\\') {
                        switch(p[1]) {
                        case '(':
                        case ')':
                        case '|':
                                addchar(p[1]);
                                break;
                        case 'w':
                                addconstantstring("[_a-zA-Z0-9]");
                                break;
                        case 'W':
                                addconstantstring("[^_a-zA-Z0-9]");
                                break;
                        case '<':
                                addconstantstring("[[:<:]]");
                                break;
                        case '>':
                                addconstantstring("[[:>:]]");
                                break;
                        default:
                                addchars(p, 2);
                                break;
                        }
                        p+=2;
                        continue;
                }
                if (*p == '(' || *p == ')' || *p == '|')
                        addchar('\\');

                addchar(*p);
                p++;
        }
        return getstring();
}

/* patsubst(string, regexp, opt replacement) */
/* argv[2]: string
 * argv[3]: regexp
 * argv[4]: opt rep
 */
void
dopatsubst(const char *argv[], int argc)
{
        if (argc <= 3) {
                m4_warnx("Too few arguments to patsubst");
                return;
        }
        /* special case: empty regexp */
        if (argv[3][0] == '\0') {
                const char *s;
                size_t len;
                if (argc > 4 && argv[4])
                        len = strlen(argv[4]);
                else
                        len = 0;
                for (s = argv[2]; *s != '\0'; s++) {
                        addchars(argv[4], len);
                        addchar(*s);
                }
        } else {
                int error;
                regex_t re;
                regmatch_t *pmatch;
                int mode = REG_EXTENDED;
                const char *source;
                size_t l = strlen(argv[3]);

                if (!mimic_gnu ||
                    (argv[3][0] == '^') ||
                    (l > 0 && argv[3][l-1] == '$'))
                        mode |= REG_NEWLINE;

                source = mimic_gnu ? twiddle(argv[3]) : argv[3];
                error = regcomp(&re, source, mode);
                if (error != 0)
                        exit_regerror(error, &re, source);

                pmatch = xreallocarray(NULL, re.re_nsub+1, sizeof(regmatch_t), 
                    NULL);
                do_subst(argv[2], &re, source,
                    argc > 4 && argv[4] != NULL ? argv[4] : "", pmatch);
                free(pmatch);
                regfree(&re);
        }
        pbstr(getstring());
}

void
doregexp(const char *argv[], int argc)
{
        int error;
        regex_t re;
        regmatch_t *pmatch;
        const char *source;

        if (argc <= 3) {
                m4_warnx("Too few arguments to regexp");
                return;
        }
        /* special gnu case */
        if (argv[3][0] == '\0' && mimic_gnu) {
                if (argc == 4 || argv[4] == NULL)
                        return;
                else
                        pbstr(argv[4]);
        }
        source = mimic_gnu ? twiddle(argv[3]) : argv[3];
        error = regcomp(&re, source, REG_EXTENDED|REG_NEWLINE);
        if (error != 0)
                exit_regerror(error, &re, source);

        pmatch = xreallocarray(NULL, re.re_nsub+1, sizeof(regmatch_t), NULL);
        if (argc == 4 || argv[4] == NULL)
                do_regexpindex(argv[2], &re, source, pmatch);
        else
                do_regexp(argv[2], &re, source, argv[4], pmatch);
        free(pmatch);
        regfree(&re);
}

void
doformat(const char *argv[], int argc)
{
        const char *format = argv[2];
        int pos = 3;
        int left_padded;
        long width;
        size_t l;
        const char *thisarg;
        char temp[2];
        long extra;

        while (*format != 0) {
                if (*format != '%') {
                        addchar(*format++);
                        continue;
                }

                format++;
                if (*format == '%') {
                        addchar(*format++);
                        continue;
                }
                if (*format == 0) {
                        addchar('%');
                        break;
                }

                if (*format == '*') {
                        format++;
                        if (pos >= argc)
                                m4errx(1,
                                    "Format with too many format specifiers.");
                        width = strtol(argv[pos++], NULL, 10);
                } else {
                        width = strtol(format, (char **)&format, 10);
                }
                if (width < 0) {
                        left_padded = 1;
                        width = -width;
                } else {
                        left_padded = 0;
                }
                if (*format == '.') {
                        format++;
                        if (*format == '*') {
                                format++;
                                if (pos >= argc)
                                        m4errx(1,
                                            "Format with too many format specifiers.");
                                extra = strtol(argv[pos++], NULL, 10);
                        } else {
                                extra = strtol(format, (char **)&format, 10);
                        }
                } else {
                        extra = LONG_MAX;
                }
                if (pos >= argc)
                        m4errx(1, "Format with too many format specifiers.");
                switch(*format) {
                case 's':
                        thisarg = argv[pos++];
                        break;
                case 'c':
                        temp[0] = strtoul(argv[pos++], NULL, 10);
                        temp[1] = 0;
                        thisarg = temp;
                        break;
                default:
                        m4errx(1, "Unsupported format specification: %s.",
                            argv[2]);
                }
                format++;
                l = strlen(thisarg);
                if (l > extra)
                        l = extra;
                if (!left_padded) {
                        while (l < width--)
                                addchar(' ');
                }
                addchars(thisarg, l);
                if (left_padded) {
                        while (l < width--)
                                addchar(' ');
                }
        }
        pbstr(getstring());
}

void
doesyscmd(const char *cmd)
{
        int p[2];
        pid_t cpid;
        char *argv[4];
        int cc;
        int status;

        /* Follow gnu m4 documentation: first flush buffers. */
        fflush(NULL);

        argv[0] = "sh";
        argv[1] = "-c";
        argv[2] = (char *)cmd;
        argv[3] = NULL;

        /* Just set up standard output, share stderr and stdin with m4 */
        if (pipe(p) == -1)
                err(1, "bad pipe");
        switch(cpid = fork()) {
        case -1:
                err(1, "bad fork");
                /* NOTREACHED */
        case 0:
                (void) close(p[0]);
                (void) dup2(p[1], 1);
                (void) close(p[1]);
                execv(_PATH_BSHELL, argv);
                exit(1);
        default:
                /* Read result in two stages, since m4's buffer is
                 * pushback-only. */
                (void) close(p[1]);
                do {
                        char result[BUFSIZE];
                        cc = read(p[0], result, sizeof result);
                        if (cc > 0)
                                addchars(result, cc);
                } while (cc > 0 || (cc == -1 && errno == EINTR));

                (void) close(p[0]);
                while (waitpid(cpid, &status, 0) == -1) {
                        if (errno != EINTR)
                                break;
                }
                pbstr(getstring());
        }
}

void
getdivfile(const char *name)
{
        FILE *f;
        int c;

        f = fopen(name, "r");
        if (!f)
                return;

        while ((c = getc(f))!= EOF)
                putc(c, active);
        (void) fclose(f);
}