/*
 * Copyright (c) 2002 - 2014 Tony Finch <dot@dotat.at>
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

/*
 * unifdef - remove ifdef'ed lines
 *
 * This code was derived from software contributed to Berkeley by Dave Yost.
 * It was rewritten to support ANSI C by Tony Finch. The original version
 * of unifdef carried the 4-clause BSD copyright licence. None of its code
 * remains in this version (though some of the names remain) so it now
 * carries a more liberal licence.
 *
 *  Wishlist:
 *      provide an option which will append the name of the
 *        appropriate symbol after #else's and #endif's
 *      provide an option which will check symbols after
 *        #else's and #endif's to see that they match their
 *        corresponding #ifdef or #ifndef
 *
 *   These require better buffer handling, which would also make
 *   it possible to handle all "dodgy" directives correctly.
 */

#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static const char copyright[] =
    #include "version.h"
    "@(#) $Author: deraadt $\n"
    "@(#) $URL: http://dotat.at/prog/unifdef $\n"
;

/* types of input lines: */
typedef enum {
        LT_TRUEI,               /* a true #if with ignore flag */
        LT_FALSEI,              /* a false #if with ignore flag */
        LT_IF,                  /* an unknown #if */
        LT_TRUE,                /* a true #if */
        LT_FALSE,               /* a false #if */
        LT_ELIF,                /* an unknown #elif */
        LT_ELTRUE,              /* a true #elif */
        LT_ELFALSE,             /* a false #elif */
        LT_ELSE,                /* #else */
        LT_ENDIF,               /* #endif */
        LT_DODGY,               /* flag: directive is not on one line */
        LT_DODGY_LAST = LT_DODGY + LT_ENDIF,
        LT_PLAIN,               /* ordinary line */
        LT_EOF,                 /* end of file */
        LT_ERROR,               /* unevaluable #if */
        LT_COUNT
} Linetype;

static char const * const linetype_name[] = {
        "TRUEI", "FALSEI", "IF", "TRUE", "FALSE",
        "ELIF", "ELTRUE", "ELFALSE", "ELSE", "ENDIF",
        "DODGY TRUEI", "DODGY FALSEI",
        "DODGY IF", "DODGY TRUE", "DODGY FALSE",
        "DODGY ELIF", "DODGY ELTRUE", "DODGY ELFALSE",
        "DODGY ELSE", "DODGY ENDIF",
        "PLAIN", "EOF", "ERROR"
};

#define linetype_if2elif(lt) ((Linetype)(lt - LT_IF + LT_ELIF))
#define linetype_2dodgy(lt) ((Linetype)(lt + LT_DODGY))

/* state of #if processing */
typedef enum {
        IS_OUTSIDE,
        IS_FALSE_PREFIX,        /* false #if followed by false #elifs */
        IS_TRUE_PREFIX,         /* first non-false #(el)if is true */
        IS_PASS_MIDDLE,         /* first non-false #(el)if is unknown */
        IS_FALSE_MIDDLE,        /* a false #elif after a pass state */
        IS_TRUE_MIDDLE,         /* a true #elif after a pass state */
        IS_PASS_ELSE,           /* an else after a pass state */
        IS_FALSE_ELSE,          /* an else after a true state */
        IS_TRUE_ELSE,           /* an else after only false states */
        IS_FALSE_TRAILER,       /* #elifs after a true are false */
        IS_COUNT
} Ifstate;

static char const * const ifstate_name[] = {
        "OUTSIDE", "FALSE_PREFIX", "TRUE_PREFIX",
        "PASS_MIDDLE", "FALSE_MIDDLE", "TRUE_MIDDLE",
        "PASS_ELSE", "FALSE_ELSE", "TRUE_ELSE",
        "FALSE_TRAILER"
};

/* state of comment parser */
typedef enum {
        NO_COMMENT = false,     /* outside a comment */
        C_COMMENT,              /* in a comment like this one */
        CXX_COMMENT,            /* between // and end of line */
        STARTING_COMMENT,       /* just after slash-backslash-newline */
        FINISHING_COMMENT,      /* star-backslash-newline in a C comment */
        CHAR_LITERAL,           /* inside '' */
        STRING_LITERAL          /* inside "" */
} Comment_state;

static char const * const comment_name[] = {
        "NO", "C", "CXX", "STARTING", "FINISHING", "CHAR", "STRING"
};

/* state of preprocessor line parser */
typedef enum {
        LS_START,               /* only space and comments on this line */
        LS_HASH,                /* only space, comments, and a hash */
        LS_DIRTY                /* this line can't be a preprocessor line */
} Line_state;

static char const * const linestate_name[] = {
        "START", "HASH", "DIRTY"
};

/*
 * Minimum translation limits from ISO/IEC 9899:1999 5.2.4.1
 */
#define MAXDEPTH        64                      /* maximum #if nesting */
#define MAXLINE         4096                    /* maximum length of line */
#define MAXSYMS         16384                   /* maximum number of symbols */

/*
 * Sometimes when editing a keyword the replacement text is longer, so
 * we leave some space at the end of the tline buffer to accommodate this.
 */
#define EDITSLOP        10

/*
 * Globals.
 */

static bool             compblank;              /* -B: compress blank lines */
static bool             lnblank;                /* -b: blank deleted lines */
static bool             complement;             /* -c: do the complement */
static bool             debugging;              /* -d: debugging reports */
static bool             inplace;                /* -m: modify in place */
static bool             iocccok;                /* -e: fewer IOCCC errors */
static bool             strictlogic;            /* -K: keep ambiguous #ifs */
static bool             killconsts;             /* -k: eval constant #ifs */
static bool             lnnum;                  /* -n: add #line directives */
static bool             symlist;                /* -s: output symbol list */
static bool             symdepth;               /* -S: output symbol depth */
static bool             text;                   /* -t: this is a text file */

static const char      *symname[MAXSYMS];       /* symbol name */
static const char      *value[MAXSYMS];         /* -Dsym=value */
static bool             ignore[MAXSYMS];        /* -iDsym or -iUsym */
static int              nsyms;                  /* number of symbols */

static FILE            *input;                  /* input file pointer */
static const char      *filename;               /* input file name */
static int              linenum;                /* current line number */
static const char      *linefile;               /* file name for #line */
static FILE            *output;                 /* output file pointer */
static const char      *ofilename;              /* output file name */
static const char      *backext;                /* backup extension */
static char            *tempname;               /* avoid splatting input */

static char             tline[MAXLINE+EDITSLOP];/* input buffer plus space */
static char            *keyword;                /* used for editing #elif's */

/*
 * When processing a file, the output's newline style will match the
 * input's, and unifdef correctly handles CRLF or LF endings whatever
 * the platform's native style. The stdio streams are opened in binary
 * mode to accommodate platforms whose native newline style is CRLF.
 * When the output isn't a processed input file (when it is error /
 * debug / diagnostic messages) then unifdef uses native line endings.
 */

static const char      *newline;                /* input file format */
static const char       newline_unix[] = "\n";
static const char       newline_crlf[] = "\r\n";

static Comment_state    incomment;              /* comment parser state */
static Line_state       linestate;              /* #if line parser state */
static Ifstate          ifstate[MAXDEPTH];      /* #if processor state */
static bool             ignoring[MAXDEPTH];     /* ignore comments state */
static int              stifline[MAXDEPTH];     /* start of current #if */
static int              depth;                  /* current #if nesting */
static int              delcount;               /* count of deleted lines */
static unsigned         blankcount;             /* count of blank lines */
static unsigned         blankmax;               /* maximum recent blankcount */
static bool             constexpr;              /* constant #if expression */
static bool             zerosyms;               /* to format symdepth output */
static bool             firstsym;               /* ditto */

static int              exitmode;               /* exit status mode */
static int              exitstat;               /* program exit status */

static void             addsym1(bool, bool, char *);
static void             addsym2(bool, const char *, const char *);
static char            *astrcat(const char *, const char *);
static void             cleantemp(void);
static void             closeio(void);
static void             debug(const char *, ...);
static void             debugsym(const char *, int);
static bool             defundef(void);
static void             defundefile(const char *);
static void             done(void);
static void             error(const char *);
static int              findsym(const char **);
static void             flushline(bool);
static void             hashline(void);
static void             help(void);
static Linetype         ifeval(const char **);
static void             ignoreoff(void);
static void             ignoreon(void);
static void             indirectsym(void);
static void             keywordedit(const char *);
static const char      *matchsym(const char *, const char *);
static void             nest(void);
static Linetype         parseline(void);
static void             process(void);
static void             processinout(const char *, const char *);
static const char      *skipargs(const char *);
static const char      *skipcomment(const char *);
static const char      *skiphash(void);
static const char      *skipline(const char *);
static const char      *skipsym(const char *);
static void             state(Ifstate);
static void             unnest(void);
static void             usage(void);
static void             version(void);
static const char      *xstrdup(const char *, const char *);
static FILE *           mktempmode(char *tmp, int mode);

#define endsym(c) (!isalnum((unsigned char)c) && c != '_')

/*
 * The main program.
 */
int
main(int argc, char *argv[])
{
        const char *errstr;
        int opt;

        if (pledge("stdio rpath wpath cpath fattr", NULL) == -1)
                err(1, "pledge");

        while ((opt = getopt(argc, argv, "i:D:U:f:I:M:o:x:bBcdehKklmnsStV")) != -1)
                switch (opt) {
                case 'i': /* treat stuff controlled by these symbols as text */
                        /*
                         * For strict backwards-compatibility the U or D
                         * should be immediately after the -i but it doesn't
                         * matter much if we relax that requirement.
                         */
                        opt = *optarg++;
                        if (opt == 'D')
                                addsym1(true, true, optarg);
                        else if (opt == 'U')
                                addsym1(true, false, optarg);
                        else
                                usage();
                        break;
                case 'D': /* define a symbol */
                        addsym1(false, true, optarg);
                        break;
                case 'U': /* undef a symbol */
                        addsym1(false, false, optarg);
                        break;
                case 'I': /* no-op for compatibility with cpp */
                        break;
                case 'b': /* blank deleted lines instead of omitting them */
                case 'l': /* backwards compatibility */
                        lnblank = true;
                        break;
                case 'B': /* compress blank lines around removed section */
                        compblank = true;
                        break;
                case 'c': /* treat -D as -U and vice versa */
                        complement = true;
                        break;
                case 'd':
                        debugging = true;
                        break;
                case 'e': /* fewer errors from dodgy lines */
                        iocccok = true;
                        break;
                case 'f': /* definitions file */
                        defundefile(optarg);
                        break;
                case 'h':
                        help();
                        break;
                case 'K': /* keep ambiguous #ifs */
                        strictlogic = true;
                        break;
                case 'k': /* process constant #ifs */
                        killconsts = true;
                        break;
                case 'm': /* modify in place */
                        inplace = true;
                        break;
                case 'M': /* modify in place and keep backup */
                        inplace = true;
                        backext = optarg;
                        break;
                case 'n': /* add #line directive after deleted lines */
                        lnnum = true;
                        break;
                case 'o': /* output to a file */
                        ofilename = optarg;
                        break;
                case 's': /* only output list of symbols that control #ifs */
                        symlist = true;
                        break;
                case 'S': /* list symbols with their nesting depth */
                        symlist = symdepth = true;
                        break;
                case 't': /* don't parse C comments */
                        text = true;
                        break;
                case 'V':
                        version();
                        break;
                case 'x':
                        exitmode = strtonum(optarg, 0, 2, &errstr);
                        if (errstr)
                                errx(1, "-x %s: %s", optarg, errstr);
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;
        if (compblank && lnblank)
                errx(2, "-B and -b are mutually exclusive");
        if (symlist && (ofilename != NULL || inplace || argc > 1))
                errx(2, "-s only works with one input file");
        if (argc > 1 && ofilename != NULL)
                errx(2, "-o cannot be used with multiple input files");
        if (argc > 1 && !inplace)
                errx(2, "multiple input files require -m or -M");
        if (argc == 0 && inplace)
                errx(2, "can't edit stdin in place");
        if (argc == 0)
                argc = 1;
        if (argc == 1 && !inplace && ofilename == NULL)
                ofilename = "-";
        indirectsym();

        atexit(cleantemp);
        if (ofilename != NULL)
                processinout(*argv, ofilename);
        else while (argc-- > 0) {
                processinout(*argv, *argv);
                argv++;
        }
        switch(exitmode) {
        case(0): exit(exitstat);
        case(1): exit(!exitstat);
        case(2): exit(0);
        default: abort(); /* bug */
        }
}

/*
 * File logistics.
 */
static void
processinout(const char *ifn, const char *ofn)
{
        struct stat st;

        if (ifn == NULL || strcmp(ifn, "-") == 0) {
                filename = "[stdin]";
                linefile = NULL;
                input = stdin;
        } else {
                filename = ifn;
                linefile = ifn;
                input = fopen(ifn, "rb");
                if (input == NULL)
                        err(2, "can't open %s", ifn);
        }
        if (strcmp(ofn, "-") == 0) {
                output = stdout;
                process();
                return;
        }
        if (stat(ofn, &st) == -1) {
                output = fopen(ofn, "wb");
                if (output == NULL)
                        err(2, "can't create %s", ofn);
                process();
                return;
        }

        tempname = astrcat(ofn, ".XXXXXX");
        output = mktempmode(tempname, st.st_mode);
        if (output == NULL)
                err(2, "can't create %s", tempname);

        process();

        if (backext != NULL && *backext != '\0') {
                char *backname = astrcat(ofn, backext);
                if (rename(ofn, backname) == -1)
                        err(2, "can't rename \"%s\" to \"%s\"", ofn, backname);
                free(backname);
        }
        if (rename(tempname, ofn) == -1)
                err(2, "can't rename \"%s\" to \"%s\"", tempname, ofn);
        free(tempname);
        tempname = NULL;
}

/*
 * For cleaning up if there is an error.
 */
static void
cleantemp(void)
{
        if (tempname != NULL)
                remove(tempname);
}

/*
 * Self-identification functions.
 */

static void
version(void)
{
        const char *c = copyright;
        for (;;) {
                while (*++c != '$')
                        if (*c == '\0')
                                exit(0);
                while (*++c != '$')
                        putc(*c, stderr);
                putc('\n', stderr);
        }
}

static void
synopsis(FILE *fp)
{
        fprintf(fp,
            "usage:     unifdef [-BbcdehKkmnSstV] [-[i]Dsym[=val]] [-[i]Usym] [-f defile]\n"
            "           [-M backext] [-o outfile] [-x 0 | 1 | 2] file ...\n");
}

static void
usage(void)
{
        synopsis(stderr);
        exit(2);
}

static void
help(void)
{
        synopsis(stdout);
        printf(
            "   -Dsym=val  define preprocessor symbol with given value\n"
            "   -Dsym      define preprocessor symbol with value 1\n"
            "   -Usym      preprocessor symbol is undefined\n"
            "   -iDsym=val \\  ignore C strings and comments\n"
            "   -iDsym      ) in sections controlled by these\n"
            "   -iUsym     /  preprocessor symbols\n"
            "   -fpath  file containing #define and #undef directives\n"
            "   -b      blank lines instead of deleting them\n"
            "   -B      compress blank lines around deleted section\n"
            "   -c      complement (invert) keep vs. delete\n"
            "   -d      debugging mode\n"
            "   -e      ignore multiline preprocessor directives\n"
            "   -h      print help\n"
            "   -Ipath  extra include file path (ignored)\n"
            "   -K      disable && and || short-circuiting\n"
            "   -k      process constant #if expressions\n"
            "   -Mext   modify in place and keep backups\n"
            "   -m      modify input files in place\n"
            "   -n      add #line directives to output\n"
            "   -opath  output file name\n"
            "   -S      list #if control symbols with nesting\n"
            "   -s      list #if control symbols\n"
            "   -t      ignore C strings and comments\n"
            "   -V      print version\n"
            "   -x{012} exit status mode\n"
        );
        exit(0);
}

/*
 * A state transition function alters the global #if processing state
 * in a particular way. The table below is indexed by the current
 * processing state and the type of the current line.
 *
 * Nesting is handled by keeping a stack of states; some transition
 * functions increase or decrease the depth. They also maintain the
 * ignore state on a stack. In some complicated cases they have to
 * alter the preprocessor directive, as follows.
 *
 * When we have processed a group that starts off with a known-false
 * #if/#elif sequence (which has therefore been deleted) followed by a
 * #elif that we don't understand and therefore must keep, we edit the
 * latter into a #if to keep the nesting correct. We use memcpy() to
 * overwrite the 4 byte token "elif" with "if  " without a '\0' byte.
 *
 * When we find a true #elif in a group, the following block will
 * always be kept and the rest of the sequence after the next #elif or
 * #else will be discarded. We edit the #elif into a #else and the
 * following directive to #endif since this has the desired behaviour.
 *
 * "Dodgy" directives are split across multiple lines, the most common
 * example being a multi-line comment hanging off the right of the
 * directive. We can handle them correctly only if there is no change
 * from printing to dropping (or vice versa) caused by that directive.
 * If the directive is the first of a group we have a choice between
 * failing with an error, or passing it through unchanged instead of
 * evaluating it. The latter is not the default to avoid questions from
 * users about unifdef unexpectedly leaving behind preprocessor directives.
 */
typedef void state_fn(void);

/* report an error */
static void Eelif (void) { error("Inappropriate #elif"); }
static void Eelse (void) { error("Inappropriate #else"); }
static void Eendif(void) { error("Inappropriate #endif"); }
static void Eeof  (void) { error("Premature EOF"); }
static void Eioccc(void) { error("Obfuscated preprocessor control line"); }
/* plain line handling */
static void print (void) { flushline(true); }
static void drop  (void) { flushline(false); }
/* output lacks group's start line */
static void Strue (void) { drop();  ignoreoff(); state(IS_TRUE_PREFIX); }
static void Sfalse(void) { drop();  ignoreoff(); state(IS_FALSE_PREFIX); }
static void Selse (void) { drop();               state(IS_TRUE_ELSE); }
/* print/pass this block */
static void Pelif (void) { print(); ignoreoff(); state(IS_PASS_MIDDLE); }
static void Pelse (void) { print();              state(IS_PASS_ELSE); }
static void Pendif(void) { print(); unnest(); }
/* discard this block */
static void Dfalse(void) { drop();  ignoreoff(); state(IS_FALSE_TRAILER); }
static void Delif (void) { drop();  ignoreoff(); state(IS_FALSE_MIDDLE); }
static void Delse (void) { drop();               state(IS_FALSE_ELSE); }
static void Dendif(void) { drop();  unnest(); }
/* first line of group */
static void Fdrop (void) { nest();  Dfalse(); }
static void Fpass (void) { nest();  Pelif(); }
static void Ftrue (void) { nest();  Strue(); }
static void Ffalse(void) { nest();  Sfalse(); }
/* variable pedantry for obfuscated lines */
static void Oiffy (void) { if (!iocccok) Eioccc(); Fpass(); ignoreon(); }
static void Oif   (void) { if (!iocccok) Eioccc(); Fpass(); }
static void Oelif (void) { if (!iocccok) Eioccc(); Pelif(); }
/* ignore comments in this block */
static void Idrop (void) { Fdrop();  ignoreon(); }
static void Itrue (void) { Ftrue();  ignoreon(); }
static void Ifalse(void) { Ffalse(); ignoreon(); }
/* modify this line */
static void Mpass (void) { memcpy(keyword, "if  ", 4); Pelif(); }
static void Mtrue (void) { keywordedit("else");  state(IS_TRUE_MIDDLE); }
static void Melif (void) { keywordedit("endif"); state(IS_FALSE_TRAILER); }
static void Melse (void) { keywordedit("endif"); state(IS_FALSE_ELSE); }

static state_fn * const trans_table[IS_COUNT][LT_COUNT] = {
/* IS_OUTSIDE */
{ Itrue, Ifalse,Fpass, Ftrue, Ffalse,Eelif, Eelif, Eelif, Eelse, Eendif,
  Oiffy, Oiffy, Fpass, Oif,   Oif,   Eelif, Eelif, Eelif, Eelse, Eendif,
  print, done,  abort },
/* IS_FALSE_PREFIX */
{ Idrop, Idrop, Fdrop, Fdrop, Fdrop, Mpass, Strue, Sfalse,Selse, Dendif,
  Idrop, Idrop, Fdrop, Fdrop, Fdrop, Mpass, Eioccc,Eioccc,Eioccc,Eioccc,
  drop,  Eeof,  abort },
/* IS_TRUE_PREFIX */
{ Itrue, Ifalse,Fpass, Ftrue, Ffalse,Dfalse,Dfalse,Dfalse,Delse, Dendif,
  Oiffy, Oiffy, Fpass, Oif,   Oif,   Eioccc,Eioccc,Eioccc,Eioccc,Eioccc,
  print, Eeof,  abort },
/* IS_PASS_MIDDLE */
{ Itrue, Ifalse,Fpass, Ftrue, Ffalse,Pelif, Mtrue, Delif, Pelse, Pendif,
  Oiffy, Oiffy, Fpass, Oif,   Oif,   Pelif, Oelif, Oelif, Pelse, Pendif,
  print, Eeof,  abort },
/* IS_FALSE_MIDDLE */
{ Idrop, Idrop, Fdrop, Fdrop, Fdrop, Pelif, Mtrue, Delif, Pelse, Pendif,
  Idrop, Idrop, Fdrop, Fdrop, Fdrop, Eioccc,Eioccc,Eioccc,Eioccc,Eioccc,
  drop,  Eeof,  abort },
/* IS_TRUE_MIDDLE */
{ Itrue, Ifalse,Fpass, Ftrue, Ffalse,Melif, Melif, Melif, Melse, Pendif,
  Oiffy, Oiffy, Fpass, Oif,   Oif,   Eioccc,Eioccc,Eioccc,Eioccc,Pendif,
  print, Eeof,  abort },
/* IS_PASS_ELSE */
{ Itrue, Ifalse,Fpass, Ftrue, Ffalse,Eelif, Eelif, Eelif, Eelse, Pendif,
  Oiffy, Oiffy, Fpass, Oif,   Oif,   Eelif, Eelif, Eelif, Eelse, Pendif,
  print, Eeof,  abort },
/* IS_FALSE_ELSE */
{ Idrop, Idrop, Fdrop, Fdrop, Fdrop, Eelif, Eelif, Eelif, Eelse, Dendif,
  Idrop, Idrop, Fdrop, Fdrop, Fdrop, Eelif, Eelif, Eelif, Eelse, Eioccc,
  drop,  Eeof,  abort },
/* IS_TRUE_ELSE */
{ Itrue, Ifalse,Fpass, Ftrue, Ffalse,Eelif, Eelif, Eelif, Eelse, Dendif,
  Oiffy, Oiffy, Fpass, Oif,   Oif,   Eelif, Eelif, Eelif, Eelse, Eioccc,
  print, Eeof,  abort },
/* IS_FALSE_TRAILER */
{ Idrop, Idrop, Fdrop, Fdrop, Fdrop, Dfalse,Dfalse,Dfalse,Delse, Dendif,
  Idrop, Idrop, Fdrop, Fdrop, Fdrop, Dfalse,Dfalse,Dfalse,Delse, Eioccc,
  drop,  Eeof,  abort }
/*TRUEI  FALSEI IF     TRUE   FALSE  ELIF   ELTRUE ELFALSE ELSE  ENDIF
  TRUEI  FALSEI IF     TRUE   FALSE  ELIF   ELTRUE ELFALSE ELSE  ENDIF (DODGY)
  PLAIN  EOF    ERROR */
};

/*
 * State machine utility functions
 */
static void
ignoreoff(void)
{
        if (depth == 0)
                abort(); /* bug */
        ignoring[depth] = ignoring[depth-1];
}
static void
ignoreon(void)
{
        ignoring[depth] = true;
}
static void
keywordedit(const char *replacement)
{
        snprintf(keyword, tline + sizeof(tline) - keyword,
            "%s%s", replacement, newline);
        print();
}
static void
nest(void)
{
        if (depth > MAXDEPTH-1)
                abort(); /* bug */
        if (depth == MAXDEPTH-1)
                error("Too many levels of nesting");
        depth += 1;
        stifline[depth] = linenum;
}
static void
unnest(void)
{
        if (depth == 0)
                abort(); /* bug */
        depth -= 1;
}
static void
state(Ifstate is)
{
        ifstate[depth] = is;
}

/*
 * The last state transition function. When this is called,
 * lineval == LT_EOF, so the process() loop will terminate.
 */
static void
done(void)
{
        if (incomment)
                error("EOF in comment");
        closeio();
}

/*
 * Write a line to the output or not, according to command line options.
 * If writing fails, closeio() will print the error and exit.
 */
static void
flushline(bool keep)
{
        if (symlist)
                return;
        if (keep ^ complement) {
                bool blankline = tline[strspn(tline, " \t\r\n")] == '\0';
                if (blankline && compblank && blankcount != blankmax) {
                        delcount += 1;
                        blankcount += 1;
                } else {
                        if (lnnum && delcount > 0)
                                hashline();
                        if (fputs(tline, output) == EOF)
                                closeio();
                        delcount = 0;
                        blankmax = blankcount = blankline ? blankcount + 1 : 0;
                }
        } else {
                if (lnblank && fputs(newline, output) == EOF)
                        closeio();
                exitstat = 1;
                delcount += 1;
                blankcount = 0;
        }
        if (debugging && fflush(output) == EOF)
                closeio();
}

/*
 * Format of #line directives depends on whether we know the input filename.
 */
static void
hashline(void)
{
        int e;

        if (linefile == NULL)
                e = fprintf(output, "#line %d%s", linenum, newline);
        else
                e = fprintf(output, "#line %d \"%s\"%s",
                    linenum, linefile, newline);
        if (e < 0)
                closeio();
}

/*
 * Flush the output and handle errors.
 */
static void
closeio(void)
{
        /* Tidy up after findsym(). */
        if (symdepth && !zerosyms)
                printf("\n");
        if (output != NULL && (ferror(output) || fclose(output) == EOF))
                        err(2, "%s: can't write to output", filename);
        fclose(input);
}

/*
 * The driver for the state machine.
 */
static void
process(void)
{
        Linetype lineval = LT_PLAIN;
        /* When compressing blank lines, act as if the file
           is preceded by a large number of blank lines. */
        blankmax = blankcount = 1000;
        zerosyms = true;
        newline = NULL;
        linenum = 0;
        while (lineval != LT_EOF) {
                lineval = parseline();
                trans_table[ifstate[depth]][lineval]();
                debug("process line %d %s -> %s depth %d",
                    linenum, linetype_name[lineval],
                    ifstate_name[ifstate[depth]], depth);
        }
}

/*
 * Parse a line and determine its type. We keep the preprocessor line
 * parser state between calls in the global variable linestate, with
 * help from skipcomment().
 */
static Linetype
parseline(void)
{
        const char *cp;
        int cursym;
        Linetype retval;
        Comment_state wascomment;

        wascomment = incomment;
        cp = skiphash();
        if (cp == NULL)
                return (LT_EOF);
        if (newline == NULL) {
                if (strrchr(tline, '\n') == strrchr(tline, '\r') + 1)
                        newline = newline_crlf;
                else
                        newline = newline_unix;
        }
        if (*cp == '\0') {
                retval = LT_PLAIN;
                goto done;
        }
        keyword = tline + (cp - tline);
        if ((cp = matchsym("ifdef", keyword)) != NULL ||
            (cp = matchsym("ifndef", keyword)) != NULL) {
                cp = skipcomment(cp);
                if ((cursym = findsym(&cp)) < 0)
                        retval = LT_IF;
                else {
                        retval = (keyword[2] == 'n')
                            ? LT_FALSE : LT_TRUE;
                        if (value[cursym] == NULL)
                                retval = (retval == LT_TRUE)
                                    ? LT_FALSE : LT_TRUE;
                        if (ignore[cursym])
                                retval = (retval == LT_TRUE)
                                    ? LT_TRUEI : LT_FALSEI;
                }
        } else if ((cp = matchsym("if", keyword)) != NULL)
                retval = ifeval(&cp);
        else if ((cp = matchsym("elif", keyword)) != NULL)
                retval = linetype_if2elif(ifeval(&cp));
        else if ((cp = matchsym("else", keyword)) != NULL)
                retval = LT_ELSE;
        else if ((cp = matchsym("endif", keyword)) != NULL)
                retval = LT_ENDIF;
        else {
                cp = skipsym(keyword);
                /* no way can we deal with a continuation inside a keyword */
                if (strncmp(cp, "\\\r\n", 3) == 0 ||
                    strncmp(cp, "\\\n", 2) == 0)
                        Eioccc();
                cp = skipline(cp);
                retval = LT_PLAIN;
                goto done;
        }
        cp = skipcomment(cp);
        if (*cp != '\0') {
                cp = skipline(cp);
                if (retval == LT_TRUE || retval == LT_FALSE ||
                    retval == LT_TRUEI || retval == LT_FALSEI)
                        retval = LT_IF;
                if (retval == LT_ELTRUE || retval == LT_ELFALSE)
                        retval = LT_ELIF;
        }
        /* the following can happen if the last line of the file lacks a
           newline or if there is too much whitespace in a directive */
        if (linestate == LS_HASH) {
                long len = cp - tline;
                if (fgets(tline + len, MAXLINE - len, input) == NULL) {
                        if (ferror(input))
                                err(2, "can't read %s", filename);
                        /* append the missing newline at eof */
                        strlcpy(tline + len, newline, sizeof(tline) - len);
                        cp += strlen(newline);
                        linestate = LS_START;
                } else {
                        linestate = LS_DIRTY;
                }
        }
        if (retval != LT_PLAIN && (wascomment || linestate != LS_START)) {
                retval = linetype_2dodgy(retval);
                linestate = LS_DIRTY;
        }
done:
        debug("parser line %d state %s comment %s line", linenum,
            comment_name[incomment], linestate_name[linestate]);
        return (retval);
}

/*
 * These are the binary operators that are supported by the expression
 * evaluator.
 */
static Linetype op_strict(long *p, long v, Linetype at, Linetype bt) {
        if(at == LT_IF || bt == LT_IF) return (LT_IF);
        return (*p = v, v ? LT_TRUE : LT_FALSE);
}
static Linetype op_lt(long *p, Linetype at, long a, Linetype bt, long b) {
        return op_strict(p, a < b, at, bt);
}
static Linetype op_gt(long *p, Linetype at, long a, Linetype bt, long b) {
        return op_strict(p, a > b, at, bt);
}
static Linetype op_le(long *p, Linetype at, long a, Linetype bt, long b) {
        return op_strict(p, a <= b, at, bt);
}
static Linetype op_ge(long *p, Linetype at, long a, Linetype bt, long b) {
        return op_strict(p, a >= b, at, bt);
}
static Linetype op_eq(long *p, Linetype at, long a, Linetype bt, long b) {
        return op_strict(p, a == b, at, bt);
}
static Linetype op_ne(long *p, Linetype at, long a, Linetype bt, long b) {
        return op_strict(p, a != b, at, bt);
}
static Linetype op_or(long *p, Linetype at, long a, Linetype bt, long b) {
        if (!strictlogic && (at == LT_TRUE || bt == LT_TRUE))
                return (*p = 1, LT_TRUE);
        return op_strict(p, a || b, at, bt);
}
static Linetype op_and(long *p, Linetype at, long a, Linetype bt, long b) {
        if (!strictlogic && (at == LT_FALSE || bt == LT_FALSE))
                return (*p = 0, LT_FALSE);
        return op_strict(p, a && b, at, bt);
}

/*
 * An evaluation function takes three arguments, as follows: (1) a pointer to
 * an element of the precedence table which lists the operators at the current
 * level of precedence; (2) a pointer to an integer which will receive the
 * value of the expression; and (3) a pointer to a char* that points to the
 * expression to be evaluated and that is updated to the end of the expression
 * when evaluation is complete. The function returns LT_FALSE if the value of
 * the expression is zero, LT_TRUE if it is non-zero, LT_IF if the expression
 * depends on an unknown symbol, or LT_ERROR if there is a parse failure.
 */
struct ops;

typedef Linetype eval_fn(const struct ops *, long *, const char **);

static eval_fn eval_table, eval_unary;

/*
 * The precedence table. Expressions involving binary operators are evaluated
 * in a table-driven way by eval_table. When it evaluates a subexpression it
 * calls the inner function with its first argument pointing to the next
 * element of the table. Innermost expressions have special non-table-driven
 * handling.
 */
struct op {
        const char *str;
        Linetype (*fn)(long *, Linetype, long, Linetype, long);
};
struct ops {
        eval_fn *inner;
        struct op op[5];
};
static const struct ops eval_ops[] = {
        { eval_table, { { "||", op_or } } },
        { eval_table, { { "&&", op_and } } },
        { eval_table, { { "==", op_eq },
                        { "!=", op_ne } } },
        { eval_unary, { { "<=", op_le },
                        { ">=", op_ge },
                        { "<", op_lt },
                        { ">", op_gt } } }
};

/* Current operator precedence level */
static long prec(const struct ops *ops)
{
        return (ops - eval_ops);
}

/*
 * Function for evaluating the innermost parts of expressions,
 * viz. !expr (expr) number defined(symbol) symbol
 * We reset the constexpr flag in the last two cases.
 */
static Linetype
eval_unary(const struct ops *ops, long *valp, const char **cpp)
{
        const char *cp;
        char *ep;
        int sym;
        bool defparen;
        Linetype lt;

        cp = skipcomment(*cpp);
        if (*cp == '!') {
                debug("eval%d !", prec(ops));
                cp++;
                lt = eval_unary(ops, valp, &cp);
                if (lt == LT_ERROR)
                        return (LT_ERROR);
                if (lt != LT_IF) {
                        *valp = !*valp;
                        lt = *valp ? LT_TRUE : LT_FALSE;
                }
        } else if (*cp == '(') {
                cp++;
                debug("eval%d (", prec(ops));
                lt = eval_table(eval_ops, valp, &cp);
                if (lt == LT_ERROR)
                        return (LT_ERROR);
                cp = skipcomment(cp);
                if (*cp++ != ')')
                        return (LT_ERROR);
        } else if (isdigit((unsigned char)*cp)) {
                debug("eval%d number", prec(ops));
                *valp = strtol(cp, &ep, 0);
                if (ep == cp)
                        return (LT_ERROR);
                lt = *valp ? LT_TRUE : LT_FALSE;
                cp = ep;
        } else if (matchsym("defined", cp) != NULL) {
                cp = skipcomment(cp+7);
                if (*cp == '(') {
                        cp = skipcomment(cp+1);
                        defparen = true;
                } else {
                        defparen = false;
                }
                sym = findsym(&cp);
                cp = skipcomment(cp);
                if (defparen && *cp++ != ')') {
                        debug("eval%d defined missing ')'", prec(ops));
                        return (LT_ERROR);
                }
                if (sym < 0) {
                        debug("eval%d defined unknown", prec(ops));
                        lt = LT_IF;
                } else {
                        debug("eval%d defined %s", prec(ops), symname[sym]);
                        *valp = (value[sym] != NULL);
                        lt = *valp ? LT_TRUE : LT_FALSE;
                }
                constexpr = false;
        } else if (!endsym(*cp)) {
                debug("eval%d symbol", prec(ops));
                sym = findsym(&cp);
                if (sym < 0) {
                        lt = LT_IF;
                        cp = skipargs(cp);
                } else if (value[sym] == NULL) {
                        *valp = 0;
                        lt = LT_FALSE;
                } else {
                        *valp = strtol(value[sym], &ep, 0);
                        if (*ep != '\0' || ep == value[sym])
                                return (LT_ERROR);
                        lt = *valp ? LT_TRUE : LT_FALSE;
                        cp = skipargs(cp);
                }
                constexpr = false;
        } else {
                debug("eval%d bad expr", prec(ops));
                return (LT_ERROR);
        }

        *cpp = cp;
        debug("eval%d = %d", prec(ops), *valp);
        return (lt);
}

/*
 * Table-driven evaluation of binary operators.
 */
static Linetype
eval_table(const struct ops *ops, long *valp, const char **cpp)
{
        const struct op *op;
        const char *cp;
        long val;
        Linetype lt, rt;

        debug("eval%d", prec(ops));
        cp = *cpp;
        lt = ops->inner(ops+1, valp, &cp);
        if (lt == LT_ERROR)
                return (LT_ERROR);
        for (;;) {
                cp = skipcomment(cp);
                for (op = ops->op; op->str != NULL; op++)
                        if (strncmp(cp, op->str, strlen(op->str)) == 0)
                                break;
                if (op->str == NULL)
                        break;
                cp += strlen(op->str);
                debug("eval%d %s", prec(ops), op->str);
                rt = ops->inner(ops+1, &val, &cp);
                if (rt == LT_ERROR)
                        return (LT_ERROR);
                lt = op->fn(valp, lt, *valp, rt, val);
        }

        *cpp = cp;
        debug("eval%d = %d", prec(ops), *valp);
        debug("eval%d lt = %s", prec(ops), linetype_name[lt]);
        return (lt);
}

/*
 * Evaluate the expression on a #if or #elif line. If we can work out
 * the result we return LT_TRUE or LT_FALSE accordingly, otherwise we
 * return just a generic LT_IF.
 */
static Linetype
ifeval(const char **cpp)
{
        Linetype ret;
        long val = 0;

        debug("eval %s", *cpp);
        constexpr = killconsts ? false : true;
        ret = eval_table(eval_ops, &val, cpp);
        debug("eval = %d", val);
        return (constexpr ? LT_IF : ret == LT_ERROR ? LT_IF : ret);
}

/*
 * Read a line and examine its initial part to determine if it is a
 * preprocessor directive. Returns NULL on EOF, or a pointer to a
 * preprocessor directive name, or a pointer to the zero byte at the
 * end of the line.
 */
static const char *
skiphash(void)
{
        const char *cp;

        linenum++;
        if (fgets(tline, MAXLINE, input) == NULL) {
                if (ferror(input))
                        err(2, "can't read %s", filename);
                else
                        return (NULL);
        }
        cp = skipcomment(tline);
        if (linestate == LS_START && *cp == '#') {
                linestate = LS_HASH;
                return (skipcomment(cp + 1));
        } else if (*cp == '\0') {
                return (cp);
        } else {
                return (skipline(cp));
        }
}

/*
 * Mark a line dirty and consume the rest of it, keeping track of the
 * lexical state.
 */
static const char *
skipline(const char *cp)
{
        const char *pcp;
        if (*cp != '\0')
                linestate = LS_DIRTY;
        while (*cp != '\0') {
                cp = skipcomment(pcp = cp);
                if (pcp == cp)
                        cp++;
        }
        return (cp);
}

/*
 * Skip over comments, strings, and character literals and stop at the
 * next character position that is not whitespace. Between calls we keep
 * the comment state in the global variable incomment, and we also adjust
 * the global variable linestate when we see a newline.
 * XXX: doesn't cope with the buffer splitting inside a state transition.
 */
static const char *
skipcomment(const char *cp)
{
        if (text || ignoring[depth]) {
                for (; isspace((unsigned char)*cp); cp++)
                        if (*cp == '\n')
                                linestate = LS_START;
                return (cp);
        }
        while (*cp != '\0')
                /* don't reset to LS_START after a line continuation */
                if (strncmp(cp, "\\\r\n", 3) == 0)
                        cp += 3;
                else if (strncmp(cp, "\\\n", 2) == 0)
                        cp += 2;
                else switch (incomment) {
                case NO_COMMENT:
                        if (strncmp(cp, "/\\\r\n", 4) == 0) {
                                incomment = STARTING_COMMENT;
                                cp += 4;
                        } else if (strncmp(cp, "/\\\n", 3) == 0) {
                                incomment = STARTING_COMMENT;
                                cp += 3;
                        } else if (strncmp(cp, "/*", 2) == 0) {
                                incomment = C_COMMENT;
                                cp += 2;
                        } else if (strncmp(cp, "//", 2) == 0) {
                                incomment = CXX_COMMENT;
                                cp += 2;
                        } else if (strncmp(cp, "\'", 1) == 0) {
                                incomment = CHAR_LITERAL;
                                linestate = LS_DIRTY;
                                cp += 1;
                        } else if (strncmp(cp, "\"", 1) == 0) {
                                incomment = STRING_LITERAL;
                                linestate = LS_DIRTY;
                                cp += 1;
                        } else if (strncmp(cp, "\n", 1) == 0) {
                                linestate = LS_START;
                                cp += 1;
                        } else if (strchr(" \r\t", *cp) != NULL) {
                                cp += 1;
                        } else
                                return (cp);
                        continue;
                case CXX_COMMENT:
                        if (strncmp(cp, "\n", 1) == 0) {
                                incomment = NO_COMMENT;
                                linestate = LS_START;
                        }
                        cp += 1;
                        continue;
                case CHAR_LITERAL:
                case STRING_LITERAL:
                        if ((incomment == CHAR_LITERAL && cp[0] == '\'') ||
                            (incomment == STRING_LITERAL && cp[0] == '\"')) {
                                incomment = NO_COMMENT;
                                cp += 1;
                        } else if (cp[0] == '\\') {
                                if (cp[1] == '\0')
                                        cp += 1;
                                else
                                        cp += 2;
                        } else if (strncmp(cp, "\n", 1) == 0) {
                                if (incomment == CHAR_LITERAL)
                                        error("Unterminated char literal");
                                else
                                        error("Unterminated string literal");
                        } else
                                cp += 1;
                        continue;
                case C_COMMENT:
                        if (strncmp(cp, "*\\\r\n", 4) == 0) {
                                incomment = FINISHING_COMMENT;
                                cp += 4;
                        } else if (strncmp(cp, "*\\\n", 3) == 0) {
                                incomment = FINISHING_COMMENT;
                                cp += 3;
                        } else if (strncmp(cp, "*/", 2) == 0) {
                                incomment = NO_COMMENT;
                                cp += 2;
                        } else
                                cp += 1;
                        continue;
                case STARTING_COMMENT:
                        if (*cp == '*') {
                                incomment = C_COMMENT;
                                cp += 1;
                        } else if (*cp == '/') {
                                incomment = CXX_COMMENT;
                                cp += 1;
                        } else {
                                incomment = NO_COMMENT;
                                linestate = LS_DIRTY;
                        }
                        continue;
                case FINISHING_COMMENT:
                        if (*cp == '/') {
                                incomment = NO_COMMENT;
                                cp += 1;
                        } else
                                incomment = C_COMMENT;
                        continue;
                default:
                        abort(); /* bug */
                }
        return (cp);
}

/*
 * Skip macro arguments.
 */
static const char *
skipargs(const char *cp)
{
        const char *ocp = cp;
        int level = 0;
        cp = skipcomment(cp);
        if (*cp != '(')
                return (cp);
        do {
                if (*cp == '(')
                        level++;
                if (*cp == ')')
                        level--;
                cp = skipcomment(cp+1);
        } while (level != 0 && *cp != '\0');
        if (level == 0)
                return (cp);
        else
        /* Rewind and re-detect the syntax error later. */
                return (ocp);
}

/*
 * Skip over an identifier.
 */
static const char *
skipsym(const char *cp)
{
        while (!endsym(*cp))
                ++cp;
        return (cp);
}

/*
 * Skip whitespace and take a copy of any following identifier.
 */
static const char *
getsym(const char **cpp)
{
        const char *cp = *cpp, *sym;

        cp = skipcomment(cp);
        cp = skipsym(sym = cp);
        if (cp == sym)
                return NULL;
        *cpp = cp;
        return (xstrdup(sym, cp));
}

/*
 * Check that s (a symbol) matches the start of t, and that the
 * following character in t is not a symbol character. Returns a
 * pointer to the following character in t if there is a match,
 * otherwise NULL.
 */
static const char *
matchsym(const char *s, const char *t)
{
        while (*s != '\0' && *t != '\0')
                if (*s != *t)
                        return (NULL);
                else
                        ++s, ++t;
        if (*s == '\0' && endsym(*t))
                return(t);
        else
                return(NULL);
}

/*
 * Look for the symbol in the symbol table. If it is found, we return
 * the symbol table index, else we return -1.
 */
static int
findsym(const char **strp)
{
        const char *str;
        int symind;

        str = *strp;
        *strp = skipsym(str);
        if (symlist) {
                if (*strp == str)
                        return (-1);
                if (symdepth && firstsym)
                        printf("%s%3d", zerosyms ? "" : "\n", depth);
                firstsym = zerosyms = false;
                printf("%s%.*s%s",
                       symdepth ? " " : "",
                       (int)(*strp-str), str,
                       symdepth ? "" : "\n");
                /* we don't care about the value of the symbol */
                return (0);
        }
        for (symind = 0; symind < nsyms; ++symind) {
                if (matchsym(symname[symind], str) != NULL) {
                        debugsym("findsym", symind);
                        return (symind);
                }
        }
        return (-1);
}

/*
 * Resolve indirect symbol values to their final definitions.
 */
static void
indirectsym(void)
{
        const char *cp;
        int changed, sym, ind;

        do {
                changed = 0;
                for (sym = 0; sym < nsyms; ++sym) {
                        if (value[sym] == NULL)
                                continue;
                        cp = value[sym];
                        ind = findsym(&cp);
                        if (ind == -1 || ind == sym ||
                            *cp != '\0' ||
                            value[ind] == NULL ||
                            value[ind] == value[sym])
                                continue;
                        debugsym("indir...", sym);
                        value[sym] = value[ind];
                        debugsym("...ectsym", sym);
                        changed++;
                }
        } while (changed);
}

/*
 * Add a symbol to the symbol table, specified with the format sym=val
 */
static void
addsym1(bool ignorethis, bool definethis, char *symval)
{
        const char *sym, *val;

        sym = symval;
        val = skipsym(sym);
        if (definethis && *val == '=') {
                symval[val - sym] = '\0';
                val = val + 1;
        } else if (*val == '\0') {
                val = definethis ? "1" : NULL;
        } else {
                usage();
        }
        addsym2(ignorethis, sym, val);
}

/*
 * Add a symbol to the symbol table.
 */
static void
addsym2(bool ignorethis, const char *sym, const char *val)
{
        const char *cp = sym;
        int symind;

        symind = findsym(&cp);
        if (symind < 0) {
                if (nsyms >= MAXSYMS)
                        errx(2, "too many symbols");
                symind = nsyms++;
        }
        ignore[symind] = ignorethis;
        symname[symind] = sym;
        value[symind] = val;
        debugsym("addsym", symind);
}

static void
debugsym(const char *why, int symind)
{
        debug("%s %s%c%s", why, symname[symind],
            value[symind] ? '=' : ' ',
            value[symind] ? value[symind] : "undef");
}

/*
 * Add symbols to the symbol table from a file containing
 * #define and #undef preprocessor directives.
 */
static void
defundefile(const char *fn)
{
        filename = fn;
        input = fopen(fn, "rb");
        if (input == NULL)
                err(2, "can't open %s", fn);
        linenum = 0;
        while (defundef())
                ;
        if (ferror(input))
                err(2, "can't read %s", filename);
        else
                fclose(input);
        if (incomment)
                error("EOF in comment");
}

/*
 * Read and process one #define or #undef directive
 */
static bool
defundef(void)
{
        const char *cp, *kw, *sym, *val, *end;

        cp = skiphash();
        if (cp == NULL)
                return (false);
        if (*cp == '\0')
                goto done;
        /* strip trailing whitespace, and do a fairly rough check to
           avoid unsupported multi-line preprocessor directives */
        end = cp + strlen(cp);
        while (end > tline && strchr(" \t\n\r", end[-1]) != NULL)
                --end;
        if (end > tline && end[-1] == '\\')
                Eioccc();

        kw = cp;
        if ((cp = matchsym("define", kw)) != NULL) {
                sym = getsym(&cp);
                if (sym == NULL)
                        error("Missing macro name in #define");
                if (*cp == '(') {
                        val = "1";
                } else {
                        cp = skipcomment(cp);
                        val = (cp < end) ? xstrdup(cp, end) : "";
                }
                debug("#define");
                addsym2(false, sym, val);
        } else if ((cp = matchsym("undef", kw)) != NULL) {
                sym = getsym(&cp);
                if (sym == NULL)
                        error("Missing macro name in #undef");
                cp = skipcomment(cp);
                debug("#undef");
                addsym2(false, sym, NULL);
        } else {
                error("Unrecognized preprocessor directive");
        }
        skipline(cp);
done:
        debug("parser line %d state %s comment %s line", linenum,
            comment_name[incomment], linestate_name[linestate]);
        return (true);
}

/*
 * Concatenate two strings into new memory, checking for failure.
 */
static char *
astrcat(const char *s1, const char *s2)
{
        char *s;

        if (asprintf(&s, "%s%s", s1, s2) == -1)
                err(2, "asprintf");
        return (s);
}

/*
 * Duplicate a segment of a string, checking for failure.
 */
static const char *
xstrdup(const char *start, const char *end)
{
        size_t n;
        char *s;

        if (end < start) abort(); /* bug */
        n = (size_t)(end - start) + 1;
        s = (char *)malloc(n);
        if (s == NULL)
                err(2, "malloc");
        snprintf(s, n, "%s", start);
        return (s);
}

/*
 * Diagnostics.
 */
static void
debug(const char *msg, ...)
{
        va_list ap;

        if (debugging) {
                va_start(ap, msg);
                vwarnx(msg, ap);
                va_end(ap);
        }
}

static void
error(const char *msg)
{
        if (depth == 0)
                warnx("%s: %d: %s", filename, linenum, msg);
        else
                warnx("%s: %d: %s (#if line %d depth %d)",
                    filename, linenum, msg, stifline[depth], depth);
        closeio();
        errx(2, "Output may be truncated");
}

static FILE *
mktempmode(char *tmp, int mode)
{
        int fd = mkstemp(tmp);
        if (fd == -1)
                return (NULL);
        fchmod(fd, mode & (S_IRWXU|S_IRWXG|S_IRWXO));
        return (fdopen(fd, "wb"));
}