Quelle unifdef.c Sprache: C

/*
* Copyright (c) 2002 - 2011 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/types.h>
#include <sys/stat.h>

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

const char copyright[] =
    "@(#) $Version: unifdef-2.5 $\n"
    "@(#) $Author: Tony Finch (dot@dotat.at) $\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"
};

/* 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         4096   /* 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

/*
* For temporary filenames
*/
#define TEMPLATE        "unifdef.XXXXXX"

/*
* 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             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 FILE            *output;   /* output file pointer */
static const char      *ofilename;  /* output file name */
static bool             overwriting;  /* output overwrites input */
static char             tempname[FILENAME_MAX]; /* used when overwriting */

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

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             constexpression; /* constant #if expression */
static bool             zerosyms = true; /* to format symdepth output */
static bool             firstsym;  /* ditto */

static int              exitstat;  /* program exit status */

static void             addsym(bool, bool, char *);
static void             closeout(void);
static void             debug(const char *, ...);
static void             done(void);
static void             error(const char *);
static int              findsym(const char *);
static void             flushline(bool);
static Linetype         parseline(void);
static Linetype         ifeval(const char **);
static void             ignoreoff(void);
static void             ignoreon(void);
static void             keywordedit(const char *);
static void             nest(void);
static void             process(void);
static const char      *skipargs(const char *);
static const char      *skipcomment(const char *);
static const char      *skipsym(const char *);
static void             state(Ifstate);
static int              strlcmp(const char *, const char *, size_t);
static void             unnest(void);
static void             usage(void);
static void             version(void);

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

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

while ((opt = getopt(argc, argv, "i:D:U:I:o:bBcdeKklnsStV")) != -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')
    addsym(true, true, optarg);
   else if (opt == 'U')
    addsym(true, false, optarg);
   else
    usage();
   break;
  case 'D': /* define a symbol */
   addsym(false, true, optarg);
   break;
  case 'U': /* undef a symbol */
   addsym(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 'K': /* keep ambiguous #ifs */
   strictlogic = true;
   break;
  case 'k': /* process constant #ifs */
   killconsts = true;
   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': /* print version */
   version();
  default:
   usage();
  }
argc -= optind;
argv += optind;
if (compblank && lnblank)
  errx(2, "-B and -b are mutually exclusive");
if (argc > 1) {
  errx(2, "can only do one file");
} else if (argc == 1 && strcmp(*argv, "-") != 0) {
  filename = *argv;
  input = fopen(filename, "rb");
  if (input == NULL)
   err(2, "can't open %s", filename);
} else {
  filename = "[stdin]";
  input = stdin;
}
if (ofilename == NULL) {
  ofilename = "[stdout]";
  output = stdout;
} else {
  struct stat ist, ost;
  if (stat(ofilename, &ost) == 0 &&
      fstat(fileno(input), &ist) == 0)
   overwriting = (ist.st_dev == ost.st_dev
        && ist.st_ino == ost.st_ino);
  if (overwriting) {
   const char *dirsep;
   int ofd;

   dirsep = strrchr(ofilename, '/');
   if (dirsep != NULL)
    snprintf(tempname, sizeof(tempname),
        "%.*s/" TEMPLATE,
        (int)(dirsep - ofilename), ofilename);
   else
    snprintf(tempname, sizeof(tempname),
        TEMPLATE);
   ofd = mkstemp(tempname);
   if (ofd != -1)
    output = fdopen(ofd, "wb+");
   if (output == NULL)
    err(2, "can't create temporary file");
   fchmod(ofd, ist.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO));
  } else {
   output = fopen(ofilename, "wb");
   if (output == NULL)
    err(2, "can't open %s", ofilename);
  }
}
process();
abort(); /* bug */
}

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
usage(void)
{
fprintf(stderr, "usage: unifdef [-bBcdeKknsStV] [-Ipath]"
     " [-Dsym[=val]] [-Usym] [-iDsym[=val]] [-iUsym] ... [file]\n");
exit(2);
}

/*
* 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;
}

/*
* Write a line to the output or not, according to command line options.
*/
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)
    printf("#line %d%s", linenum, newline);
   fputs(tline, output);
   delcount = 0;
   blankmax = blankcount = blankline ? blankcount + 1 : 0;
  }
} else {
  if (lnblank)
   fputs(newline, output);
  exitstat = 1;
  delcount += 1;
  blankcount = 0;
}
if (debugging)
  fflush(output);
}

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

/*
* Flush the output and handle errors.
*/
static void
closeout(void)
{
if (symdepth && !zerosyms)
  printf("\n");
if (fclose(output) == EOF) {
  warn("couldn't write to %s", ofilename);
  if (overwriting) {
   unlink(tempname);
   errx(2, "%s unchanged", filename);
  } else {
   exit(2);
  }
}
}

/*
* Clean up and exit.
*/
static void
done(void)
{
if (incomment)
  error("EOF in comment");
closeout();
if (overwriting && rename(tempname, ofilename) == -1) {
  warn("couldn't rename temporary file");
  unlink(tempname);
  errx(2, "%s unchanged", ofilename);
}
exit(exitstat);
}

/*
* 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;
int kwlen;
Linetype retval;
Comment_state wascomment;

linenum++;
if (fgets(tline, MAXLINE, input) == NULL)
  return (LT_EOF);
if (newline == NULL) {
  if (strrchr(tline, '\n') == strrchr(tline, '\r') + 1)
   newline = newline_crlf;
  else
   newline = newline_unix;
}
retval = LT_PLAIN;
wascomment = incomment;
cp = skipcomment(tline);
if (linestate == LS_START) {
  if (*cp == '#') {
   linestate = LS_HASH;
   firstsym = true;
   cp = skipcomment(cp + 1);
  } else if (*cp != '\0')
   linestate = LS_DIRTY;
}
if (!incomment && linestate == LS_HASH) {
  keyword = tline + (cp - tline);
  cp = skipsym(cp);
  kwlen = cp - 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();
  if (strlcmp("ifdef", keyword, kwlen) == 0 ||
      strlcmp("ifndef", keyword, kwlen) == 0) {
   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;
   }
   cp = skipsym(cp);
  } else if (strlcmp("if", keyword, kwlen) == 0)
   retval = ifeval(&cp);
  else if (strlcmp("elif", keyword, kwlen) == 0)
   retval = ifeval(&cp) - LT_IF + LT_ELIF;
  else if (strlcmp("else", keyword, kwlen) == 0)
   retval = LT_ELSE;
  else if (strlcmp("endif", keyword, kwlen) == 0)
   retval = LT_ENDIF;
  else {
   linestate = LS_DIRTY;
   retval = LT_PLAIN;
  }
  cp = skipcomment(cp);
  if (*cp != '\0') {
   linestate = LS_DIRTY;
   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;
  }
  if (retval != LT_PLAIN && (wascomment || incomment)) {
   retval += LT_DODGY;
   if (incomment)
    linestate = LS_DIRTY;
  }
  /* skipcomment normally changes the state, except
   if the last line of the file lacks a newline, or
   if there is too much whitespace in a directive */
  if (linestate == LS_HASH) {
   size_t len = cp - tline;
   if (fgets(tline + len, MAXLINE - len, input) == NULL) {
    /* append the missing newline */
    strcpy(tline + len, newline);
    cp += strlen(newline);
    linestate = LS_START;
   } else {
    linestate = LS_DIRTY;
   }
  }
}
if (linestate == LS_DIRTY) {
  while (*cp != '\0')
   cp = skipcomment(cp + 1);
}
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(int *p, int 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(int *p, Linetype at, int a, Linetype bt, int b) {
return op_strict(p, a < b, at, bt);
}
static Linetype op_gt(int *p, Linetype at, int a, Linetype bt, int b) {
return op_strict(p, a > b, at, bt);
}
static Linetype op_le(int *p, Linetype at, int a, Linetype bt, int b) {
return op_strict(p, a <= b, at, bt);
}
static Linetype op_ge(int *p, Linetype at, int a, Linetype bt, int b) {
return op_strict(p, a >= b, at, bt);
}
static Linetype op_eq(int *p, Linetype at, int a, Linetype bt, int b) {
return op_strict(p, a == b, at, bt);
}
static Linetype op_ne(int *p, Linetype at, int a, Linetype bt, int b) {
return op_strict(p, a != b, at, bt);
}
static Linetype op_or(int *p, Linetype at, int a, Linetype bt, int 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(int *p, Linetype at, int a, Linetype bt, int 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 *, int *, 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.
*/
static const struct ops {
eval_fn *inner;
struct op {
  const char *str;
  Linetype (*fn)(int *, Linetype, int, Linetype, int);
} op[5];
} 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 } } }
};

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

cp = skipcomment(*cpp);
if (*cp == '!') {
  debug("eval%d !", ops - eval_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 (", ops - eval_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", ops - eval_ops);
  *valp = strtol(cp, &ep, 0);
  if (ep == cp)
   return (LT_ERROR);
  lt = *valp ? LT_TRUE : LT_FALSE;
  cp = skipsym(cp);
} else if (strncmp(cp, "defined", 7) == 0 && endsym(cp[7])) {
  cp = skipcomment(cp+7);
  debug("eval%d defined", ops - eval_ops);
  if (*cp == '(') {
   cp = skipcomment(cp+1);
   defparen = true;
  } else {
   defparen = false;
  }
  sym = findsym(cp);
  if (sym < 0) {
   lt = LT_IF;
  } else {
   *valp = (value[sym] != NULL);
   lt = *valp ? LT_TRUE : LT_FALSE;
  }
  cp = skipsym(cp);
  cp = skipcomment(cp);
  if (defparen && *cp++ != ')')
   return (LT_ERROR);
  constexpression = false;
} else if (!endsym(*cp)) {
  debug("eval%d symbol", ops - eval_ops);
  sym = findsym(cp);
  cp = skipsym(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);
  }
  constexpression = false;
} else {
  debug("eval%d bad expr", ops - eval_ops);
  return (LT_ERROR);
}

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

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

debug("eval%d", ops - eval_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", ops - eval_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", ops - eval_ops, *valp);
debug("eval%d lt = %s", ops - eval_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)
{
int ret;
int val = 0;

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

/*
* 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);
}

/*
* 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 *str)
{
const char *cp;
int symind;

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

/*
* Add a symbol to the symbol table.
*/
static void
addsym(bool ignorethis, bool definethis, char *sym)
{
int symind;
char *val;

symind = findsym(sym);
if (symind < 0) {
  if (nsyms >= MAXSYMS)
   errx(2, "too many symbols");
  symind = nsyms++;
}
symname[symind] = sym;
ignore[symind] = ignorethis;
val = sym + (skipsym(sym) - sym);
if (definethis) {
  if (*val == '=') {
   value[symind] = val+1;
   *val = '\0';
  } else if (*val == '\0')
   value[symind] = "1";
  else
   usage();
} else {
  if (*val != '\0')
   usage();
  value[symind] = NULL;
}
debug("addsym %s=%s", symname[symind],
     value[symind] ? value[symind] : "undef");
}

/*
* Compare s with n characters of t.
* The same as strncmp() except that it checks that s[n] == '\0'.
*/
static int
strlcmp(const char *s, const char *t, size_t n)
{
while (n-- && *t != '\0')
  if (*s != *t)
   return ((unsigned char)*s - (unsigned char)*t);
  else
   ++s, ++t;
return ((unsigned char)*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);
closeout();
errx(2, "output may be truncated");
}

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