scripts/unifdef.c

   1 /*
   2  * Copyright (c) 2002 - 2005 Tony Finch <dot@dotat.at>.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to Berkeley by Dave Yost.
   5  * It was rewritten to support ANSI C by Tony Finch. The original version of
   6  * unifdef carried the following copyright notice. None of its code remains
   7  * in this version (though some of the names remain).
   8  *
   9  * Copyright (c) 1985, 1993
  10  *      The Regents of the University of California.  All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include <sys/cdefs.h>
  35
  36 #ifndef lint
  37 #if 0
  38 static const char copyright[] =
  39 "@(#) Copyright (c) 1985, 1993\n\
  40         The Regents of the University of California.  All rights reserved.\n";
  41 #endif
  42 #ifdef __IDSTRING
  43 __IDSTRING(Berkeley, "@(#)unifdef.c     8.1 (Berkeley) 6/6/93");
  44 __IDSTRING(NetBSD, "$NetBSD: unifdef.c,v 1.8 2000/07/03 02:51:36 matt Exp $");
  45 __IDSTRING(dotat, "$dotat: things/unifdef.c,v 1.171 2005/03/08 12:38:48 fanf2 Exp $");
  46 #endif
  47 #endif /* not lint */
  48 #ifdef __FBSDID
  49 __FBSDID("$FreeBSD: /repoman/r/ncvs/src/usr.bin/unifdef/unifdef.c,v 1.20 2005/05/21 09:55:09 ru Exp $");
  50 #endif
  51
  52 /*
  53  * unifdef - remove ifdef'ed lines
  54  *
  55  *  Wishlist:
  56  *      provide an option which will append the name of the
  57  *        appropriate symbol after #else's and #endif's
  58  *      provide an option which will check symbols after
  59  *        #else's and #endif's to see that they match their
  60  *        corresponding #ifdef or #ifndef
  61  *
  62  *   The first two items above require better buffer handling, which would
  63  *     also make it possible to handle all "dodgy" directives correctly.
  64  */
  65
  66 #include <ctype.h>
  67 #include <err.h>
  68 #include <stdarg.h>
  69 #include <stdbool.h>
  70 #include <stdio.h>
  71 #include <stdlib.h>
  72 #include <string.h>
  73 #include <unistd.h>
  74
  75 size_t strlcpy(char *dst, const char *src, size_t siz);
  76
  77 /* types of input lines: */
  78 typedef enum {
  79         LT_TRUEI,               /* a true #if with ignore flag */
  80         LT_FALSEI,              /* a false #if with ignore flag */
  81         LT_IF,                  /* an unknown #if */
  82         LT_TRUE,                /* a true #if */
  83         LT_FALSE,               /* a false #if */
  84         LT_ELIF,                /* an unknown #elif */
  85         LT_ELTRUE,              /* a true #elif */
  86         LT_ELFALSE,             /* a false #elif */
  87         LT_ELSE,                /* #else */
  88         LT_ENDIF,               /* #endif */
  89         LT_DODGY,               /* flag: directive is not on one line */
  90         LT_DODGY_LAST = LT_DODGY + LT_ENDIF,
  91         LT_PLAIN,               /* ordinary line */
  92         LT_EOF,                 /* end of file */
  93         LT_COUNT
  94 } Linetype;
  95
  96 static char const * const linetype_name[] = {
  97         "TRUEI", "FALSEI", "IF", "TRUE", "FALSE",
  98         "ELIF", "ELTRUE", "ELFALSE", "ELSE", "ENDIF",
  99         "DODGY TRUEI", "DODGY FALSEI",
 100         "DODGY IF", "DODGY TRUE", "DODGY FALSE",
 101         "DODGY ELIF", "DODGY ELTRUE", "DODGY ELFALSE",
 102         "DODGY ELSE", "DODGY ENDIF",
 103         "PLAIN", "EOF"
 104 };
 105
 106 /* state of #if processing */
 107 typedef enum {
 108         IS_OUTSIDE,
 109         IS_FALSE_PREFIX,        /* false #if followed by false #elifs */
 110         IS_TRUE_PREFIX,         /* first non-false #(el)if is true */
 111         IS_PASS_MIDDLE,         /* first non-false #(el)if is unknown */
 112         IS_FALSE_MIDDLE,        /* a false #elif after a pass state */
 113         IS_TRUE_MIDDLE,         /* a true #elif after a pass state */
 114         IS_PASS_ELSE,           /* an else after a pass state */
 115         IS_FALSE_ELSE,          /* an else after a true state */
 116         IS_TRUE_ELSE,           /* an else after only false states */
 117         IS_FALSE_TRAILER,       /* #elifs after a true are false */
 118         IS_COUNT
 119 } Ifstate;
 120
 121 static char const * const ifstate_name[] = {
 122         "OUTSIDE", "FALSE_PREFIX", "TRUE_PREFIX",
 123         "PASS_MIDDLE", "FALSE_MIDDLE", "TRUE_MIDDLE",
 124         "PASS_ELSE", "FALSE_ELSE", "TRUE_ELSE",
 125         "FALSE_TRAILER"
 126 };
 127
 128 /* state of comment parser */
 129 typedef enum {
 130         NO_COMMENT = false,     /* outside a comment */
 131         C_COMMENT,              /* in a comment like this one */
 132         CXX_COMMENT,            /* between // and end of line */
 133         STARTING_COMMENT,       /* just after slash-backslash-newline */
 134         FINISHING_COMMENT,      /* star-backslash-newline in a C comment */
 135         CHAR_LITERAL,           /* inside '' */
 136         STRING_LITERAL          /* inside "" */
 137 } Comment_state;
 138
 139 static char const * const comment_name[] = {
 140         "NO", "C", "CXX", "STARTING", "FINISHING", "CHAR", "STRING"
 141 };
 142
 143 /* state of preprocessor line parser */
 144 typedef enum {
 145         LS_START,               /* only space and comments on this line */
 146         LS_HASH,                /* only space, comments, and a hash */
 147         LS_DIRTY                /* this line can't be a preprocessor line */
 148 } Line_state;
 149
 150 static char const * const linestate_name[] = {
 151         "START", "HASH", "DIRTY"
 152 };
 153
 154 /*
 155  * Minimum translation limits from ISO/IEC 9899:1999 5.2.4.1
 156  */
 157 #define MAXDEPTH        64                      /* maximum #if nesting */
 158 #define MAXLINE         4096                    /* maximum length of line */
 159 #define MAXSYMS         4096                    /* maximum number of symbols */
 160
 161 /*
 162  * Sometimes when editing a keyword the replacement text is longer, so
 163  * we leave some space at the end of the tline buffer to accommodate this.
 164  */
 165 #define EDITSLOP        10
 166
 167 /*
 168  * Globals.
 169  */
 170
 171 static bool             complement;             /* -c: do the complement */
 172 static bool             debugging;              /* -d: debugging reports */
 173 static bool             iocccok;                /* -e: fewer IOCCC errors */
 174 static bool             killconsts;             /* -k: eval constant #ifs */
 175 static bool             lnblank;                /* -l: blank deleted lines */
 176 static bool             lnnum;                  /* -n: add #line directives */
 177 static bool             symlist;                /* -s: output symbol list */
 178 static bool             text;                   /* -t: this is a text file */
 179
 180 static const char      *symname[MAXSYMS];       /* symbol name */
 181 static const char      *value[MAXSYMS];         /* -Dsym=value */
 182 static bool             ignore[MAXSYMS];        /* -iDsym or -iUsym */
 183 static int              nsyms;                  /* number of symbols */
 184
 185 static FILE            *input;                  /* input file pointer */
 186 static const char      *filename;               /* input file name */
 187 static int              linenum;                /* current line number */
 188
 189 static char             tline[MAXLINE+EDITSLOP];/* input buffer plus space */
 190 static char            *keyword;                /* used for editing #elif's */
 191
 192 static Comment_state    incomment;              /* comment parser state */
 193 static Line_state       linestate;              /* #if line parser state */
 194 static Ifstate          ifstate[MAXDEPTH];      /* #if processor state */
 195 static bool             ignoring[MAXDEPTH];     /* ignore comments state */
 196 static int              stifline[MAXDEPTH];     /* start of current #if */
 197 static int              depth;                  /* current #if nesting */
 198 static int              delcount;               /* count of deleted lines */
 199 static bool             keepthis;               /* don't delete constant #if */
 200
 201 static int              exitstat;               /* program exit status */
 202
 203 static void             addsym(bool, bool, char *);
 204 static void             debug(const char *, ...);
 205 static void             done(void);
 206 static void             error(const char *);
 207 static int              findsym(const char *);
 208 static void             flushline(bool);
 209 static Linetype         get_line(void);
 210 static Linetype         ifeval(const char **);
 211 static void             ignoreoff(void);
 212 static void             ignoreon(void);
 213 static void             keywordedit(const char *);
 214 static void             nest(void);
 215 static void             process(void);
 216 static const char      *skipcomment(const char *);
 217 static const char      *skipsym(const char *);
 218 static void             state(Ifstate);
 219 static int              strlcmp(const char *, const char *, size_t);
 220 static void             unnest(void);
 221 static void             usage(void);
 222
 223 #define endsym(c) (!isalpha((unsigned char)c) && !isdigit((unsigned char)c) && c != '_')
 224
 225 /*
 226  * The main program.
 227  */
 228 int
 229 main(int argc, char *argv[])
 230 {
 231         int opt;
 232
 233         while ((opt = getopt(argc, argv, "i:D:U:I:cdeklnst")) != -1)
 234                 switch (opt) {
 235                 case 'i': /* treat stuff controlled by these symbols as text */
 236                         /*
 237                          * For strict backwards-compatibility the U or D
 238                          * should be immediately after the -i but it doesn't
 239                          * matter much if we relax that requirement.
 240                          */
 241                         opt = *optarg++;
 242                         if (opt == 'D')
 243                                 addsym(true, true, optarg);
 244                         else if (opt == 'U')
 245                                 addsym(true, false, optarg);
 246                         else
 247                                 usage();
 248                         break;
 249                 case 'D': /* define a symbol */
 250                         addsym(false, true, optarg);
 251                         break;
 252                 case 'U': /* undef a symbol */
 253                         addsym(false, false, optarg);
 254                         break;
 255                 case 'I':
 256                         /* no-op for compatibility with cpp */
 257                         break;
 258                 case 'c': /* treat -D as -U and vice versa */
 259                         complement = true;
 260                         break;
 261                 case 'd':
 262                         debugging = true;
 263                         break;
 264                 case 'e': /* fewer errors from dodgy lines */
 265                         iocccok = true;
 266                         break;
 267                 case 'k': /* process constant #ifs */
 268                         killconsts = true;
 269                         break;
 270                 case 'l': /* blank deleted lines instead of omitting them */
 271                         lnblank = true;
 272                         break;
 273                 case 'n': /* add #line directive after deleted lines */
 274                         lnnum = true;
 275                         break;
 276                 case 's': /* only output list of symbols that control #ifs */
 277                         symlist = true;
 278                         break;
 279                 case 't': /* don't parse C comments */
 280                         text = true;
 281                         break;
 282                 default:
 283                         usage();
 284                 }
 285         argc -= optind;
 286         argv += optind;
 287         if (argc > 1) {
 288                 errx(2, "can only do one file");
 289         } else if (argc == 1 && strcmp(*argv, "-") != 0) {
 290                 filename = *argv;
 291                 input = fopen(filename, "r");
 292                 if (input == NULL)
 293                         err(2, "can't open %s", filename);
 294         } else {
 295                 filename = "[stdin]";
 296                 input = stdin;
 297         }
 298         process();
 299         abort(); /* bug */
 300 }
 301
 302 static void
 303 usage(void)
 304 {
 305         fprintf(stderr, "usage: unifdef [-cdeklnst] [-Ipath]"
 306             " [-Dsym[=val]] [-Usym] [-iDsym[=val]] [-iUsym] ... [file]\n");
 307         exit(2);
 308 }
 309
 310 /*
 311  * A state transition function alters the global #if processing state
 312  * in a particular way. The table below is indexed by the current
 313  * processing state and the type of the current line.
 314  *
 315  * Nesting is handled by keeping a stack of states; some transition
 316  * functions increase or decrease the depth. They also maintain the
 317  * ignore state on a stack. In some complicated cases they have to
 318  * alter the preprocessor directive, as follows.
 319  *
 320  * When we have processed a group that starts off with a known-false
 321  * #if/#elif sequence (which has therefore been deleted) followed by a
 322  * #elif that we don't understand and therefore must keep, we edit the
 323  * latter into a #if to keep the nesting correct.
 324  *
 325  * When we find a true #elif in a group, the following block will
 326  * always be kept and the rest of the sequence after the next #elif or
 327  * #else will be discarded. We edit the #elif into a #else and the
 328  * following directive to #endif since this has the desired behaviour.
 329  *
 330  * "Dodgy" directives are split across multiple lines, the most common
 331  * example being a multi-line comment hanging off the right of the
 332  * directive. We can handle them correctly only if there is no change
 333  * from printing to dropping (or vice versa) caused by that directive.
 334  * If the directive is the first of a group we have a choice between
 335  * failing with an error, or passing it through unchanged instead of
 336  * evaluating it. The latter is not the default to avoid questions from
 337  * users about unifdef unexpectedly leaving behind preprocessor directives.
 338  */
 339 typedef void state_fn(void);
 340
 341 /* report an error */
 342 static void Eelif (void) { error("Inappropriate #elif"); }
 343 static void Eelse (void) { error("Inappropriate #else"); }
 344 static void Eendif(void) { error("Inappropriate #endif"); }
 345 static void Eeof  (void) { error("Premature EOF"); }
 346 static void Eioccc(void) { error("Obfuscated preprocessor control line"); }
 347 /* plain line handling */
 348 static void print (void) { flushline(true); }
 349 static void drop  (void) { flushline(false); }
 350 /* output lacks group's start line */
 351 static void Strue (void) { drop();  ignoreoff(); state(IS_TRUE_PREFIX); }
 352 static void Sfalse(void) { drop();  ignoreoff(); state(IS_FALSE_PREFIX); }
 353 static void Selse (void) { drop();               state(IS_TRUE_ELSE); }
 354 /* print/pass this block */
 355 static void Pelif (void) { print(); ignoreoff(); state(IS_PASS_MIDDLE); }
 356 static void Pelse (void) { print();              state(IS_PASS_ELSE); }
 357 static void Pendif(void) { print(); unnest(); }
 358 /* discard this block */
 359 static void Dfalse(void) { drop();  ignoreoff(); state(IS_FALSE_TRAILER); }
 360 static void Delif (void) { drop();  ignoreoff(); state(IS_FALSE_MIDDLE); }
 361 static void Delse (void) { drop();               state(IS_FALSE_ELSE); }
 362 static void Dendif(void) { drop();  unnest(); }
 363 /* first line of group */
 364 static void Fdrop (void) { nest();  Dfalse(); }
 365 static void Fpass (void) { nest();  Pelif(); }
 366 static void Ftrue (void) { nest();  Strue(); }
 367 static void Ffalse(void) { nest();  Sfalse(); }
 368 /* variable pedantry for obfuscated lines */
 369 static void Oiffy (void) { if (!iocccok) Eioccc(); Fpass(); ignoreon(); }
 370 static void Oif   (void) { if (!iocccok) Eioccc(); Fpass(); }
 371 static void Oelif (void) { if (!iocccok) Eioccc(); Pelif(); }
 372 /* ignore comments in this block */
 373 static void Idrop (void) { Fdrop();  ignoreon(); }
 374 static void Itrue (void) { Ftrue();  ignoreon(); }
 375 static void Ifalse(void) { Ffalse(); ignoreon(); }
 376 /* edit this line */
 377 static void Mpass (void) { strncpy(keyword, "if  ", 4); Pelif(); }
 378 static void Mtrue (void) { keywordedit("else\n");  state(IS_TRUE_MIDDLE); }
 379 static void Melif (void) { keywordedit("endif\n"); state(IS_FALSE_TRAILER); }
 380 static void Melse (void) { keywordedit("endif\n"); state(IS_FALSE_ELSE); }
 381
 382 static state_fn * const trans_table[IS_COUNT][LT_COUNT] = {
 383 /* IS_OUTSIDE */
 384 { Itrue, Ifalse,Fpass, Ftrue, Ffalse,Eelif, Eelif, Eelif, Eelse, Eendif,
 385   Oiffy, Oiffy, Fpass, Oif,   Oif,   Eelif, Eelif, Eelif, Eelse, Eendif,
 386   print, done },
 387 /* IS_FALSE_PREFIX */
 388 { Idrop, Idrop, Fdrop, Fdrop, Fdrop, Mpass, Strue, Sfalse,Selse, Dendif,
 389   Idrop, Idrop, Fdrop, Fdrop, Fdrop, Mpass, Eioccc,Eioccc,Eioccc,Eioccc,
 390   drop,  Eeof },
 391 /* IS_TRUE_PREFIX */
 392 { Itrue, Ifalse,Fpass, Ftrue, Ffalse,Dfalse,Dfalse,Dfalse,Delse, Dendif,
 393   Oiffy, Oiffy, Fpass, Oif,   Oif,   Eioccc,Eioccc,Eioccc,Eioccc,Eioccc,
 394   print, Eeof },
 395 /* IS_PASS_MIDDLE */
 396 { Itrue, Ifalse,Fpass, Ftrue, Ffalse,Pelif, Mtrue, Delif, Pelse, Pendif,
 397   Oiffy, Oiffy, Fpass, Oif,   Oif,   Pelif, Oelif, Oelif, Pelse, Pendif,
 398   print, Eeof },
 399 /* IS_FALSE_MIDDLE */
 400 { Idrop, Idrop, Fdrop, Fdrop, Fdrop, Pelif, Mtrue, Delif, Pelse, Pendif,
 401   Idrop, Idrop, Fdrop, Fdrop, Fdrop, Eioccc,Eioccc,Eioccc,Eioccc,Eioccc,
 402   drop,  Eeof },
 403 /* IS_TRUE_MIDDLE */
 404 { Itrue, Ifalse,Fpass, Ftrue, Ffalse,Melif, Melif, Melif, Melse, Pendif,
 405   Oiffy, Oiffy, Fpass, Oif,   Oif,   Eioccc,Eioccc,Eioccc,Eioccc,Pendif,
 406   print, Eeof },
 407 /* IS_PASS_ELSE */
 408 { Itrue, Ifalse,Fpass, Ftrue, Ffalse,Eelif, Eelif, Eelif, Eelse, Pendif,
 409   Oiffy, Oiffy, Fpass, Oif,   Oif,   Eelif, Eelif, Eelif, Eelse, Pendif,
 410   print, Eeof },
 411 /* IS_FALSE_ELSE */
 412 { Idrop, Idrop, Fdrop, Fdrop, Fdrop, Eelif, Eelif, Eelif, Eelse, Dendif,
 413   Idrop, Idrop, Fdrop, Fdrop, Fdrop, Eelif, Eelif, Eelif, Eelse, Eioccc,
 414   drop,  Eeof },
 415 /* IS_TRUE_ELSE */
 416 { Itrue, Ifalse,Fpass, Ftrue, Ffalse,Eelif, Eelif, Eelif, Eelse, Dendif,
 417   Oiffy, Oiffy, Fpass, Oif,   Oif,   Eelif, Eelif, Eelif, Eelse, Eioccc,
 418   print, Eeof },
 419 /* IS_FALSE_TRAILER */
 420 { Idrop, Idrop, Fdrop, Fdrop, Fdrop, Dfalse,Dfalse,Dfalse,Delse, Dendif,
 421   Idrop, Idrop, Fdrop, Fdrop, Fdrop, Dfalse,Dfalse,Dfalse,Delse, Eioccc,
 422   drop,  Eeof }
 423 /*TRUEI  FALSEI IF     TRUE   FALSE  ELIF   ELTRUE ELFALSE ELSE  ENDIF
 424   TRUEI  FALSEI IF     TRUE   FALSE  ELIF   ELTRUE ELFALSE ELSE  ENDIF (DODGY)
 425   PLAIN  EOF */
 426 };
 427
 428 /*
 429  * State machine utility functions
 430  */
 431 static void
 432 done(void)
 433 {
 434         if (incomment)
 435                 error("EOF in comment");
 436         exit(exitstat);
 437 }
 438 static void
 439 ignoreoff(void)
 440 {
 441         if (depth == 0)
 442                 abort(); /* bug */
 443         ignoring[depth] = ignoring[depth-1];
 444 }
 445 static void
 446 ignoreon(void)
 447 {
 448         ignoring[depth] = true;
 449 }
 450 static void
 451 keywordedit(const char *replacement)
 452 {
 453         size_t size = tline + sizeof(tline) - keyword;
 454         char *dst = keyword;
 455         const char *src = replacement;
 456         if (size != 0) {
 457                 while ((--size != 0) && (*src != '\0'))
 458                         *dst++ = *src++;
 459                 *dst = '\0';
 460         }
 461         print();
 462 }
 463 static void
 464 nest(void)
 465 {
 466         depth += 1;
 467         if (depth >= MAXDEPTH)
 468                 error("Too many levels of nesting");
 469         stifline[depth] = linenum;
 470 }
 471 static void
 472 unnest(void)
 473 {
 474         if (depth == 0)
 475                 abort(); /* bug */
 476         depth -= 1;
 477 }
 478 static void
 479 state(Ifstate is)
 480 {
 481         ifstate[depth] = is;
 482 }
 483
 484 /*
 485  * Write a line to the output or not, according to command line options.
 486  */
 487 static void
 488 flushline(bool keep)
 489 {
 490         if (symlist)
 491                 return;
 492         if (keep ^ complement) {
 493                 if (lnnum && delcount > 0)
 494                         printf("#line %d\n", linenum);
 495                 fputs(tline, stdout);
 496                 delcount = 0;
 497         } else {
 498                 if (lnblank)
 499                         putc('\n', stdout);
 500                 exitstat = 1;
 501                 delcount += 1;
 502         }
 503 }
 504
 505 /*
 506  * The driver for the state machine.
 507  */
 508 static void
 509 process(void)
 510 {
 511         Linetype lineval;
 512
 513         for (;;) {
 514                 linenum++;
 515                 lineval = get_line();
 516                 trans_table[ifstate[depth]][lineval]();
 517                 debug("process %s -> %s depth %d",
 518                     linetype_name[lineval],
 519                     ifstate_name[ifstate[depth]], depth);
 520         }
 521 }
 522
 523 /*
 524  * Parse a line and determine its type. We keep the preprocessor line
 525  * parser state between calls in the global variable linestate, with
 526  * help from skipcomment().
 527  */
 528 static Linetype
 529 get_line(void)
 530 {
 531         const char *cp;
 532         int cursym;
 533         int kwlen;
 534         Linetype retval;
 535         Comment_state wascomment;
 536
 537         if (fgets(tline, MAXLINE, input) == NULL)
 538                 return (LT_EOF);
 539         retval = LT_PLAIN;
 540         wascomment = incomment;
 541         cp = skipcomment(tline);
 542         if (linestate == LS_START) {
 543                 if (*cp == '#') {
 544                         linestate = LS_HASH;
 545                         cp = skipcomment(cp + 1);
 546                 } else if (*cp != '\0')
 547                         linestate = LS_DIRTY;
 548         }
 549         if (!incomment && linestate == LS_HASH) {
 550                 keyword = tline + (cp - tline);
 551                 cp = skipsym(cp);
 552                 kwlen = cp - keyword;
 553                 /* no way can we deal with a continuation inside a keyword */
 554                 if (strncmp(cp, "\\\n", 2) == 0)
 555                         Eioccc();
 556                 if (strlcmp("ifdef", keyword, kwlen) == 0 ||
 557                     strlcmp("ifndef", keyword, kwlen) == 0) {
 558                         cp = skipcomment(cp);
 559                         if ((cursym = findsym(cp)) < 0)
 560                                 retval = LT_IF;
 561                         else {
 562                                 retval = (keyword[2] == 'n')
 563                                     ? LT_FALSE : LT_TRUE;
 564                                 if (value[cursym] == NULL)
 565                                         retval = (retval == LT_TRUE)
 566                                             ? LT_FALSE : LT_TRUE;
 567                                 if (ignore[cursym])
 568                                         retval = (retval == LT_TRUE)
 569                                             ? LT_TRUEI : LT_FALSEI;
 570                         }
 571                         cp = skipsym(cp);
 572                 } else if (strlcmp("if", keyword, kwlen) == 0)
 573                         retval = ifeval(&cp);
 574                 else if (strlcmp("elif", keyword, kwlen) == 0)
 575                         retval = ifeval(&cp) - LT_IF + LT_ELIF;
 576                 else if (strlcmp("else", keyword, kwlen) == 0)
 577                         retval = LT_ELSE;
 578                 else if (strlcmp("endif", keyword, kwlen) == 0)
 579                         retval = LT_ENDIF;
 580                 else {
 581                         linestate = LS_DIRTY;
 582                         retval = LT_PLAIN;
 583                 }
 584                 cp = skipcomment(cp);
 585                 if (*cp != '\0') {
 586                         linestate = LS_DIRTY;
 587                         if (retval == LT_TRUE || retval == LT_FALSE ||
 588                             retval == LT_TRUEI || retval == LT_FALSEI)
 589                                 retval = LT_IF;
 590                         if (retval == LT_ELTRUE || retval == LT_ELFALSE)
 591                                 retval = LT_ELIF;
 592                 }
 593                 if (retval != LT_PLAIN && (wascomment || incomment)) {
 594                         retval += LT_DODGY;
 595                         if (incomment)
 596                                 linestate = LS_DIRTY;
 597                 }
 598                 /* skipcomment should have changed the state */
 599                 if (linestate == LS_HASH)
 600                         abort(); /* bug */
 601         }
 602         if (linestate == LS_DIRTY) {
 603                 while (*cp != '\0')
 604                         cp = skipcomment(cp + 1);
 605         }
 606         debug("parser %s comment %s line",
 607             comment_name[incomment], linestate_name[linestate]);
 608         return (retval);
 609 }
 610
 611 /*
 612  * These are the binary operators that are supported by the expression
 613  * evaluator. Note that if support for division is added then we also
 614  * need short-circuiting booleans because of divide-by-zero.
 615  */
 616 static int op_lt(int a, int b) { return (a < b); }
 617 static int op_gt(int a, int b) { return (a > b); }
 618 static int op_le(int a, int b) { return (a <= b); }
 619 static int op_ge(int a, int b) { return (a >= b); }
 620 static int op_eq(int a, int b) { return (a == b); }
 621 static int op_ne(int a, int b) { return (a != b); }
 622 static int op_or(int a, int b) { return (a || b); }
 623 static int op_and(int a, int b) { return (a && b); }
 624
 625 /*
 626  * An evaluation function takes three arguments, as follows: (1) a pointer to
 627  * an element of the precedence table which lists the operators at the current
 628  * level of precedence; (2) a pointer to an integer which will receive the
 629  * value of the expression; and (3) a pointer to a char* that points to the
 630  * expression to be evaluated and that is updated to the end of the expression
 631  * when evaluation is complete. The function returns LT_FALSE if the value of
 632  * the expression is zero, LT_TRUE if it is non-zero, or LT_IF if the
 633  * expression could not be evaluated.
 634  */
 635 struct ops;
 636
 637 typedef Linetype eval_fn(const struct ops *, int *, const char **);
 638
 639 static eval_fn eval_table, eval_unary;
 640
 641 /*
 642  * The precedence table. Expressions involving binary operators are evaluated
 643  * in a table-driven way by eval_table. When it evaluates a subexpression it
 644  * calls the inner function with its first argument pointing to the next
 645  * element of the table. Innermost expressions have special non-table-driven
 646  * handling.
 647  */
 648 static const struct ops {
 649         eval_fn *inner;
 650         struct op {
 651                 const char *str;
 652                 int (*fn)(int, int);
 653         } op[5];
 654 } eval_ops[] = {
 655         { eval_table, { { "||", op_or } } },
 656         { eval_table, { { "&&", op_and } } },
 657         { eval_table, { { "==", op_eq },
 658                         { "!=", op_ne } } },
 659         { eval_unary, { { "<=", op_le },
 660                         { ">=", op_ge },
 661                         { "<", op_lt },
 662                         { ">", op_gt } } }
 663 };
 664
 665 /*
 666  * Function for evaluating the innermost parts of expressions,
 667  * viz. !expr (expr) defined(symbol) symbol number
 668  * We reset the keepthis flag when we find a non-constant subexpression.
 669  */
 670 static Linetype
 671 eval_unary(const struct ops *ops, int *valp, const char **cpp)
 672 {
 673         const char *cp;
 674         char *ep;
 675         int sym;
 676
 677         cp = skipcomment(*cpp);
 678         if (*cp == '!') {
 679                 debug("eval%d !", ops - eval_ops);
 680                 cp++;
 681                 if (eval_unary(ops, valp, &cp) == LT_IF)
 682                         return (LT_IF);
 683                 *valp = !*valp;
 684         } else if (*cp == '(') {
 685                 cp++;
 686                 debug("eval%d (", ops - eval_ops);
 687                 if (eval_table(eval_ops, valp, &cp) == LT_IF)
 688                         return (LT_IF);
 689                 cp = skipcomment(cp);
 690                 if (*cp++ != ')')
 691                         return (LT_IF);
 692         } else if (isdigit((unsigned char)*cp)) {
 693                 debug("eval%d number", ops - eval_ops);
 694                 *valp = strtol(cp, &ep, 0);
 695                 cp = skipsym(cp);
 696         } else if (strncmp(cp, "defined", 7) == 0 && endsym(cp[7])) {
 697                 cp = skipcomment(cp+7);
 698                 debug("eval%d defined", ops - eval_ops);
 699                 if (*cp++ != '(')
 700                         return (LT_IF);
 701                 cp = skipcomment(cp);
 702                 sym = findsym(cp);
 703                 if (sym < 0)
 704                         return (LT_IF);
 705                 *valp = (value[sym] != NULL);
 706                 cp = skipsym(cp);
 707                 cp = skipcomment(cp);
 708                 if (*cp++ != ')')
 709                         return (LT_IF);
 710                 keepthis = false;
 711         } else if (!endsym(*cp)) {
 712                 debug("eval%d symbol", ops - eval_ops);
 713                 sym = findsym(cp);
 714                 if (sym < 0)
 715                         return (LT_IF);
 716                 if (value[sym] == NULL)
 717                         *valp = 0;
 718                 else {
 719                         *valp = strtol(value[sym], &ep, 0);
 720                         if (*ep != '\0' || ep == value[sym])
 721                                 return (LT_IF);
 722                 }
 723                 cp = skipsym(cp);
 724                 keepthis = false;
 725         } else {
 726                 debug("eval%d bad expr", ops - eval_ops);
 727                 return (LT_IF);
 728         }
 729
 730         *cpp = cp;
 731         debug("eval%d = %d", ops - eval_ops, *valp);
 732         return (*valp ? LT_TRUE : LT_FALSE);
 733 }
 734
 735 /*
 736  * Table-driven evaluation of binary operators.
 737  */
 738 static Linetype
 739 eval_table(const struct ops *ops, int *valp, const char **cpp)
 740 {
 741         const struct op *op;
 742         const char *cp;
 743         int val;
 744
 745         debug("eval%d", ops - eval_ops);
 746         cp = *cpp;
 747         if (ops->inner(ops+1, valp, &cp) == LT_IF)
 748                 return (LT_IF);
 749         for (;;) {
 750                 cp = skipcomment(cp);
 751                 for (op = ops->op; op->str != NULL; op++)
 752                         if (strncmp(cp, op->str, strlen(op->str)) == 0)
 753                                 break;
 754                 if (op->str == NULL)
 755                         break;
 756                 cp += strlen(op->str);
 757                 debug("eval%d %s", ops - eval_ops, op->str);
 758                 if (ops->inner(ops+1, &val, &cp) == LT_IF)
 759                         return (LT_IF);
 760                 *valp = op->fn(*valp, val);
 761         }
 762
 763         *cpp = cp;
 764         debug("eval%d = %d", ops - eval_ops, *valp);
 765         return (*valp ? LT_TRUE : LT_FALSE);
 766 }
 767
 768 /*
 769  * Evaluate the expression on a #if or #elif line. If we can work out
 770  * the result we return LT_TRUE or LT_FALSE accordingly, otherwise we
 771  * return just a generic LT_IF.
 772  */
 773 static Linetype
 774 ifeval(const char **cpp)
 775 {
 776         int ret;
 777         int val;
 778
 779         debug("eval %s", *cpp);
 780         keepthis = killconsts ? false : true;
 781         ret = eval_table(eval_ops, &val, cpp);
 782         debug("eval = %d", val);
 783         return (keepthis ? LT_IF : ret);
 784 }
 785
 786 /*
 787  * Skip over comments, strings, and character literals and stop at the
 788  * next character position that is not whitespace. Between calls we keep
 789  * the comment state in the global variable incomment, and we also adjust
 790  * the global variable linestate when we see a newline.
 791  * XXX: doesn't cope with the buffer splitting inside a state transition.
 792  */
 793 static const char *
 794 skipcomment(const char *cp)
 795 {
 796         if (text || ignoring[depth]) {
 797                 for (; isspace((unsigned char)*cp); cp++)
 798                         if (*cp == '\n')
 799                                 linestate = LS_START;
 800                 return (cp);
 801         }
 802         while (*cp != '\0')
 803                 /* don't reset to LS_START after a line continuation */
 804                 if (strncmp(cp, "\\\n", 2) == 0)
 805                         cp += 2;
 806                 else switch (incomment) {
 807                 case NO_COMMENT:
 808                         if (strncmp(cp, "/\\\n", 3) == 0) {
 809                                 incomment = STARTING_COMMENT;
 810                                 cp += 3;
 811                         } else if (strncmp(cp, "/*", 2) == 0) {
 812                                 incomment = C_COMMENT;
 813                                 cp += 2;
 814                         } else if (strncmp(cp, "//", 2) == 0) {
 815                                 incomment = CXX_COMMENT;
 816                                 cp += 2;
 817                         } else if (strncmp(cp, "\'", 1) == 0) {
 818                                 incomment = CHAR_LITERAL;
 819                                 linestate = LS_DIRTY;
 820                                 cp += 1;
 821                         } else if (strncmp(cp, "\"", 1) == 0) {
 822                                 incomment = STRING_LITERAL;
 823                                 linestate = LS_DIRTY;
 824                                 cp += 1;
 825                         } else if (strncmp(cp, "\n", 1) == 0) {
 826                                 linestate = LS_START;
 827                                 cp += 1;
 828                         } else if (strchr(" \t", *cp) != NULL) {
 829                                 cp += 1;
 830                         } else
 831                                 return (cp);
 832                         continue;
 833                 case CXX_COMMENT:
 834                         if (strncmp(cp, "\n", 1) == 0) {
 835                                 incomment = NO_COMMENT;
 836                                 linestate = LS_START;
 837                         }
 838                         cp += 1;
 839                         continue;
 840                 case CHAR_LITERAL:
 841                 case STRING_LITERAL:
 842                         if ((incomment == CHAR_LITERAL && cp[0] == '\'') ||
 843                             (incomment == STRING_LITERAL && cp[0] == '\"')) {
 844                                 incomment = NO_COMMENT;
 845                                 cp += 1;
 846                         } else if (cp[0] == '\\') {
 847                                 if (cp[1] == '\0')
 848                                         cp += 1;
 849                                 else
 850                                         cp += 2;
 851                         } else if (strncmp(cp, "\n", 1) == 0) {
 852                                 if (incomment == CHAR_LITERAL)
 853                                         error("unterminated char literal");
 854                                 else
 855                                         error("unterminated string literal");
 856                         } else
 857                                 cp += 1;
 858                         continue;
 859                 case C_COMMENT:
 860                         if (strncmp(cp, "*\\\n", 3) == 0) {
 861                                 incomment = FINISHING_COMMENT;
 862                                 cp += 3;
 863                         } else if (strncmp(cp, "*/", 2) == 0) {
 864                                 incomment = NO_COMMENT;
 865                                 cp += 2;
 866                         } else
 867                                 cp += 1;
 868                         continue;
 869                 case STARTING_COMMENT:
 870                         if (*cp == '*') {
 871                                 incomment = C_COMMENT;
 872                                 cp += 1;
 873                         } else if (*cp == '/') {
 874                                 incomment = CXX_COMMENT;
 875                                 cp += 1;
 876                         } else {
 877                                 incomment = NO_COMMENT;
 878                                 linestate = LS_DIRTY;
 879                         }
 880                         continue;
 881                 case FINISHING_COMMENT:
 882                         if (*cp == '/') {
 883                                 incomment = NO_COMMENT;
 884                                 cp += 1;
 885                         } else
 886                                 incomment = C_COMMENT;
 887                         continue;
 888                 default:
 889                         abort(); /* bug */
 890                 }
 891         return (cp);
 892 }
 893
 894 /*
 895  * Skip over an identifier.
 896  */
 897 static const char *
 898 skipsym(const char *cp)
 899 {
 900         while (!endsym(*cp))
 901                 ++cp;
 902         return (cp);
 903 }
 904
 905 /*
 906  * Look for the symbol in the symbol table. If is is found, we return
 907  * the symbol table index, else we return -1.
 908  */
 909 static int
 910 findsym(const char *str)
 911 {
 912         const char *cp;
 913         int symind;
 914
 915         cp = skipsym(str);
 916         if (cp == str)
 917                 return (-1);
 918         if (symlist) {
 919                 printf("%.*s\n", (int)(cp-str), str);
 920                 /* we don't care about the value of the symbol */
 921                 return (0);
 922         }
 923         for (symind = 0; symind < nsyms; ++symind) {
 924                 if (strlcmp(symname[symind], str, cp-str) == 0) {
 925                         debug("findsym %s %s", symname[symind],
 926                             value[symind] ? value[symind] : "");
 927                         return (symind);
 928                 }
 929         }
 930         return (-1);
 931 }
 932
 933 /*
 934  * Add a symbol to the symbol table.
 935  */
 936 static void
 937 addsym(bool ignorethis, bool definethis, char *sym)
 938 {
 939         int symind;
 940         char *val;
 941
 942         symind = findsym(sym);
 943         if (symind < 0) {
 944                 if (nsyms >= MAXSYMS)
 945                         errx(2, "too many symbols");
 946                 symind = nsyms++;
 947         }
 948         symname[symind] = sym;
 949         ignore[symind] = ignorethis;
 950         val = sym + (skipsym(sym) - sym);
 951         if (definethis) {
 952                 if (*val == '=') {
 953                         value[symind] = val+1;
 954                         *val = '\0';
 955                 } else if (*val == '\0')
 956                         value[symind] = "";
 957                 else
 958                         usage();
 959         } else {
 960                 if (*val != '\0')
 961                         usage();
 962                 value[symind] = NULL;
 963         }
 964 }
 965
 966 /*
 967  * Compare s with n characters of t.
 968  * The same as strncmp() except that it checks that s[n] == '\0'.
 969  */
 970 static int
 971 strlcmp(const char *s, const char *t, size_t n)
 972 {
 973         while (n-- && *t != '\0')
 974                 if (*s != *t)
 975                         return ((unsigned char)*s - (unsigned char)*t);
 976                 else
 977                         ++s, ++t;
 978         return ((unsigned char)*s);
 979 }
 980
 981 /*
 982  * Diagnostics.
 983  */
 984 static void
 985 debug(const char *msg, ...)
 986 {
 987         va_list ap;
 988
 989         if (debugging) {
 990                 va_start(ap, msg);
 991                 vwarnx(msg, ap);
 992                 va_end(ap);
 993         }
 994 }
 995
 996 static void
 997 error(const char *msg)
 998 {
 999         if (depth == 0)
1000                 warnx("%s: %d: %s", filename, linenum, msg);
1001         else
1002                 warnx("%s: %d: %s (#if line %d depth %d)",
1003                     filename, linenum, msg, stifline[depth], depth);
1004         errx(2, "output may be truncated");
1005 }