gcc/cppexp.c

   1 /* Parse C expressions for cpplib.
   2    Copyright (C) 1987, 1992, 1994, 1995, 1997, 1998, 1999, 2000, 2001,
   3    2002 Free Software Foundation.
   4    Contributed by Per Bothner, 1994.
   5
   6 This program is free software; you can redistribute it and/or modify it
   7 under the terms of the GNU General Public License as published by the
   8 Free Software Foundation; either version 2, or (at your option) any
   9 later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "cpplib.h"
  24 #include "cpphash.h"
  25
  26 /* Yield nonzero if adding two numbers with A's and B's signs can yield a
  27    number with SUM's sign, where A, B, and SUM are all C integers.  */
  28 #define possible_sum_sign(a, b, sum) ((((a) ^ (b)) | ~ ((a) ^ (sum))) < 0)
  29
  30 static void integer_overflow PARAMS ((cpp_reader *));
  31 static HOST_WIDEST_INT left_shift PARAMS ((cpp_reader *, HOST_WIDEST_INT,
  32                                            unsigned int,
  33                                            unsigned HOST_WIDEST_INT));
  34 static HOST_WIDEST_INT right_shift PARAMS ((cpp_reader *, HOST_WIDEST_INT,
  35                                             unsigned int,
  36                                             unsigned HOST_WIDEST_INT));
  37 static struct op parse_number PARAMS ((cpp_reader *, const cpp_token *));
  38 static struct op parse_defined PARAMS ((cpp_reader *));
  39 static struct op eval_token PARAMS ((cpp_reader *, const cpp_token *));
  40 static struct op *reduce PARAMS ((cpp_reader *, struct op *, enum cpp_ttype));
  41
  42 struct op
  43 {
  44   enum cpp_ttype op;
  45   uchar unsignedp;    /* True if value should be treated as unsigned.  */
  46   HOST_WIDEST_INT value; /* The value logically "right" of op.  */
  47 };
  48
  49 /* Token type abuse.  There is no "error" token, but we can't get
  50    comments in #if, so we can abuse that token type.  Similarly,
  51    create unary plus and minus operators.  */
  52 #define CPP_ERROR CPP_COMMENT
  53 #define CPP_UPLUS (CPP_LAST_CPP_OP + 1)
  54 #define CPP_UMINUS (CPP_LAST_CPP_OP + 2)
  55
  56 /* With -O2, gcc appears to produce nice code, moving the error
  57    message load and subsequent jump completely out of the main path.  */
  58 #define SYNTAX_ERROR(msgid) \
  59   do { cpp_error (pfile, DL_ERROR, msgid); goto syntax_error; } while(0)
  60 #define SYNTAX_ERROR2(msgid, arg) \
  61   do { cpp_error (pfile, DL_ERROR, msgid, arg); goto syntax_error; } while(0)
  62
  63 struct suffix
  64 {
  65   const unsigned char s[4];
  66   const unsigned char u;
  67   const unsigned char l;
  68 };
  69
  70 static const struct suffix vsuf_1[] = {
  71   { "u", 1, 0 }, { "U", 1, 0 },
  72   { "l", 0, 1 }, { "L", 0, 1 }
  73 };
  74
  75 static const struct suffix vsuf_2[] = {
  76   { "ul", 1, 1 }, { "UL", 1, 1 }, { "uL", 1, 1 }, { "Ul", 1, 1 },
  77   { "lu", 1, 1 }, { "LU", 1, 1 }, { "Lu", 1, 1 }, { "lU", 1, 1 },
  78   { "ll", 0, 2 }, { "LL", 0, 2 }
  79 };
  80
  81 static const struct suffix vsuf_3[] = {
  82   { "ull", 1, 2 }, { "ULL", 1, 2 }, { "uLL", 1, 2 }, { "Ull", 1, 2 },
  83   { "llu", 1, 2 }, { "LLU", 1, 2 }, { "LLu", 1, 2 }, { "llU", 1, 2 }
  84 };
  85
  86 /* Parse and convert what is presumably an integer in TOK.  Accepts
  87    decimal, hex, or octal with or without size suffixes.  Returned op
  88    is CPP_ERROR on error, otherwise it is a CPP_NUMBER.  */
  89 static struct op
  90 parse_number (pfile, tok)
  91      cpp_reader *pfile;
  92      const cpp_token *tok;
  93 {
  94   struct op op;
  95   const uchar *start = tok->val.str.text;
  96   const uchar *end = start + tok->val.str.len;
  97   const uchar *p = start;
  98   int c = 0, i, nsuff;
  99   unsigned HOST_WIDEST_INT n = 0, nd, MAX_over_base;
 100   int base = 10;
 101   int overflow = 0;
 102   int digit, largest_digit = 0;
 103   const struct suffix *sufftab;
 104
 105   op.unsignedp = 0;
 106
 107   if (p[0] == '0')
 108     {
 109       if (end - start >= 3 && (p[1] == 'x' || p[1] == 'X'))
 110         {
 111           p += 2;
 112           base = 16;
 113         }
 114       else
 115         {
 116           p += 1;
 117           base = 8;
 118         }
 119     }
 120
 121   /* Some buggy compilers (e.g. MPW C) seem to need both casts.  */
 122   MAX_over_base = (((unsigned HOST_WIDEST_INT) -1)
 123                    / ((unsigned HOST_WIDEST_INT) base));
 124
 125   for(; p < end; p++)
 126     {
 127       c = *p;
 128
 129       if (ISDIGIT (c)
 130           || (base == 16 && ISXDIGIT (c)))
 131         digit = hex_value (c);
 132       else
 133         break;
 134
 135       if (largest_digit < digit)
 136         largest_digit = digit;
 137       nd = n * base + digit;
 138       overflow |= MAX_over_base < n || nd < n;
 139       n = nd;
 140     }
 141
 142   if (p < end)
 143     {
 144       /* Check for a floating point constant.  Note that float constants
 145          with an exponent or suffix but no decimal point are technically
 146          invalid (C99 6.4.4.2) but accepted elsewhere.  */
 147       if ((c == '.' || c == 'F' || c == 'f')
 148           || (base == 10 && (c == 'E' || c == 'e')
 149               && p+1 < end && (p[1] == '+' || p[1] == '-'))
 150           || (base == 16 && (c == 'P' || c == 'p')
 151               && p+1 < end && (p[1] == '+' || p[1] == '-')))
 152         SYNTAX_ERROR ("floating point numbers are not valid in #if");
 153
 154       /* Determine the suffix. l means long, and u means unsigned.
 155          See the suffix tables, above.  */
 156       switch (end - p)
 157         {
 158         case 1: sufftab = vsuf_1; nsuff = ARRAY_SIZE (vsuf_1); break;
 159         case 2: sufftab = vsuf_2; nsuff = ARRAY_SIZE (vsuf_2); break;
 160         case 3: sufftab = vsuf_3; nsuff = ARRAY_SIZE (vsuf_3); break;
 161         default: goto invalid_suffix;
 162         }
 163
 164       for (i = 0; i < nsuff; i++)
 165         if (memcmp (p, sufftab[i].s, end - p) == 0)
 166           break;
 167       if (i == nsuff)
 168         goto invalid_suffix;
 169       op.unsignedp = sufftab[i].u;
 170
 171       if (CPP_WTRADITIONAL (pfile)
 172           && sufftab[i].u
 173           && ! cpp_sys_macro_p (pfile))
 174         cpp_error (pfile, DL_WARNING, "traditional C rejects the `U' suffix");
 175       if (sufftab[i].l == 2 && CPP_OPTION (pfile, pedantic)
 176           && ! CPP_OPTION (pfile, c99))
 177         cpp_error (pfile, DL_PEDWARN,
 178                    "too many 'l' suffixes in integer constant");
 179     }
 180
 181   if (base <= largest_digit)
 182     cpp_error (pfile, DL_PEDWARN,
 183                "integer constant contains digits beyond the radix");
 184
 185   if (overflow)
 186     cpp_error (pfile, DL_PEDWARN, "integer constant out of range");
 187
 188   /* If too big to be signed, consider it unsigned.  */
 189   else if ((HOST_WIDEST_INT) n < 0 && ! op.unsignedp)
 190     {
 191       if (base == 10)
 192         cpp_error (pfile, DL_WARNING,
 193                    "integer constant is so large that it is unsigned");
 194       op.unsignedp = 1;
 195     }
 196
 197   op.value = n;
 198   op.op = CPP_NUMBER;
 199   return op;
 200
 201  invalid_suffix:
 202   cpp_error (pfile, DL_ERROR, "invalid suffix '%.*s' on integer constant",
 203              (int) (end - p), p);
 204  syntax_error:
 205   op.op = CPP_ERROR;
 206   return op;
 207 }
 208
 209 /* Handle meeting "defined" in a preprocessor expression.  */
 210 static struct op
 211 parse_defined (pfile)
 212      cpp_reader *pfile;
 213 {
 214   int paren = 0;
 215   cpp_hashnode *node = 0;
 216   const cpp_token *token;
 217   struct op op;
 218   cpp_context *initial_context = pfile->context;
 219
 220   /* Don't expand macros.  */
 221   pfile->state.prevent_expansion++;
 222
 223   token = cpp_get_token (pfile);
 224   if (token->type == CPP_OPEN_PAREN)
 225     {
 226       paren = 1;
 227       token = cpp_get_token (pfile);
 228     }
 229
 230   if (token->type == CPP_NAME)
 231     {
 232       node = token->val.node;
 233       if (paren && cpp_get_token (pfile)->type != CPP_CLOSE_PAREN)
 234         {
 235           cpp_error (pfile, DL_ERROR, "missing ')' after \"defined\"");
 236           node = 0;
 237         }
 238     }
 239   else
 240     {
 241       cpp_error (pfile, DL_ERROR,
 242                  "operator \"defined\" requires an identifier");
 243       if (token->flags & NAMED_OP)
 244         {
 245           cpp_token op;
 246
 247           op.flags = 0;
 248           op.type = token->type;
 249           cpp_error (pfile, DL_ERROR,
 250                      "(\"%s\" is an alternative token for \"%s\" in C++)",
 251                      cpp_token_as_text (pfile, token),
 252                      cpp_token_as_text (pfile, &op));
 253         }
 254     }
 255
 256   if (!node)
 257     op.op = CPP_ERROR;
 258   else
 259     {
 260       if (pfile->context != initial_context)
 261         cpp_error (pfile, DL_WARNING,
 262                    "this use of \"defined\" may not be portable");
 263
 264       op.value = node->type == NT_MACRO;
 265       op.unsignedp = 0;
 266       op.op = CPP_NUMBER;
 267
 268       /* A possible controlling macro of the form #if !defined ().
 269          _cpp_parse_expr checks there was no other junk on the line.  */
 270       pfile->mi_ind_cmacro = node;
 271     }
 272
 273   pfile->state.prevent_expansion--;
 274   return op;
 275 }
 276
 277 /* Convert a token into a CPP_NUMBER (an interpreted preprocessing
 278    number or character constant, or the result of the "defined" or "#"
 279    operators), or CPP_ERROR on error.  */
 280 static struct op
 281 eval_token (pfile, token)
 282      cpp_reader *pfile;
 283      const cpp_token *token;
 284 {
 285   unsigned int temp;
 286   int unsignedp = 0;
 287   struct op op;
 288
 289   op.op = CPP_NUMBER;
 290
 291   switch (token->type)
 292     {
 293     case CPP_NUMBER:
 294       return parse_number (pfile, token);
 295
 296     case CPP_WCHAR:
 297     case CPP_CHAR:
 298       {
 299         cppchar_t result = cpp_interpret_charconst (pfile, token,
 300                                                     &temp, &unsignedp);
 301         op.value = result;
 302         /* Sign-extend the result if necessary.  */
 303         if (!unsignedp && (cppchar_signed_t) result < 0
 304             && sizeof (HOST_WIDEST_INT) > sizeof (cppchar_t))
 305           op.value |= ~(((unsigned HOST_WIDEST_INT) 1 << BITS_PER_CPPCHAR_T)
 306                         - 1);
 307       }
 308       break;
 309
 310     case CPP_NAME:
 311       if (token->val.node == pfile->spec_nodes.n_defined)
 312         return parse_defined (pfile);
 313       else if (CPP_OPTION (pfile, cplusplus)
 314                && (token->val.node == pfile->spec_nodes.n_true
 315                    || token->val.node == pfile->spec_nodes.n_false))
 316         {
 317           op.value = (token->val.node == pfile->spec_nodes.n_true);
 318
 319           /* Warn about use of true or false in #if when pedantic
 320              and stdbool.h has not been included.  */
 321           if (CPP_PEDANTIC (pfile)
 322               && ! cpp_defined (pfile, DSC("__bool_true_false_are_defined")))
 323             cpp_error (pfile, DL_PEDWARN,
 324                        "ISO C++ does not permit \"%s\" in #if",
 325                        NODE_NAME (token->val.node));
 326         }
 327       else
 328         {
 329           op.value = 0;
 330           if (CPP_OPTION (pfile, warn_undef) && !pfile->state.skip_eval)
 331             cpp_error (pfile, DL_WARNING, "\"%s\" is not defined",
 332                        NODE_NAME (token->val.node));
 333         }
 334       break;
 335
 336     default: /* CPP_HASH */
 337       if (_cpp_test_assertion (pfile, &temp))
 338         op.op = CPP_ERROR;
 339       op.value = temp;
 340     }
 341
 342   op.unsignedp = unsignedp;
 343   return op;
 344 }
 345
 346 /* Warn if appropriate on overflow.  */
 347 static void
 348 integer_overflow (pfile)
 349      cpp_reader *pfile;
 350 {
 351   if (CPP_PEDANTIC (pfile))
 352     cpp_error (pfile, DL_PEDWARN,
 353                "integer overflow in preprocessor expression");
 354 }
 355
 356 /* Handle shifting A left by B bits.  UNSIGNEDP is non-zero if A is
 357    unsigned.  */
 358 static HOST_WIDEST_INT
 359 left_shift (pfile, a, unsignedp, b)
 360      cpp_reader *pfile;
 361      HOST_WIDEST_INT a;
 362      unsigned int unsignedp;
 363      unsigned HOST_WIDEST_INT b;
 364 {
 365   if (b >= HOST_BITS_PER_WIDEST_INT)
 366     {
 367       if (! unsignedp && a != 0)
 368         integer_overflow (pfile);
 369       return 0;
 370     }
 371   else if (unsignedp)
 372     return (unsigned HOST_WIDEST_INT) a << b;
 373   else
 374     {
 375       HOST_WIDEST_INT l = a << b;
 376       if (l >> b != a)
 377         integer_overflow (pfile);
 378       return l;
 379     }
 380 }
 381
 382 /* Handle shifting A right by B bits.  UNSIGNEDP is non-zero if A is
 383    unsigned.  */
 384 static HOST_WIDEST_INT
 385 right_shift (pfile, a, unsignedp, b)
 386      cpp_reader *pfile ATTRIBUTE_UNUSED;
 387      HOST_WIDEST_INT a;
 388      unsigned int unsignedp;
 389      unsigned HOST_WIDEST_INT b;
 390 {
 391   if (b >= HOST_BITS_PER_WIDEST_INT)
 392     return unsignedp ? 0 : a >> (HOST_BITS_PER_WIDEST_INT - 1);
 393   else if (unsignedp)
 394     return (unsigned HOST_WIDEST_INT) a >> b;
 395   else
 396     return a >> b;
 397 }
 398 \f
 399 /* Operator precedence and flags table.
 400
 401 After an operator is returned from the lexer, if it has priority less
 402 than the operator on the top of the stack, we reduce the stack by one
 403 operator and repeat the test.  Since equal priorities do not reduce,
 404 this is naturally right-associative.
 405
 406 We handle left-associative operators by decrementing the priority of
 407 just-lexed operators by one, but retaining the priority of operators
 408 already on the stack.
 409
 410 The remaining cases are '(' and ')'.  We handle '(' by skipping the
 411 reduction phase completely.  ')' is given lower priority than
 412 everything else, including '(', effectively forcing a reduction of the
 413 parenthesised expression.  If there is a matching '(', the routine
 414 reduce() exits immediately.  If the normal exit route sees a ')', then
 415 there cannot have been a matching '(' and an error message is output.
 416
 417 The parser assumes all shifted operators require a left operand unless
 418 the flag NO_L_OPERAND is set.  These semantics are automatic; any
 419 extra semantics need to be handled with operator-specific code.  */
 420
 421 /* Flags.  */
 422 #define NO_L_OPERAND    (1 << 0)
 423 #define LEFT_ASSOC      (1 << 1)
 424
 425 /* Operator to priority map.  Must be in the same order as the first
 426    N entries of enum cpp_ttype.  */
 427 static const struct operator
 428 {
 429   uchar prio;
 430   uchar flags;
 431 } optab[] =
 432 {
 433   /* EQ */              {0, 0},         /* Shouldn't happen.  */
 434   /* NOT */             {16, NO_L_OPERAND},
 435   /* GREATER */         {12, LEFT_ASSOC},
 436   /* LESS */            {12, LEFT_ASSOC},
 437   /* PLUS */            {14, LEFT_ASSOC},
 438   /* MINUS */           {14, LEFT_ASSOC},
 439   /* MULT */            {15, LEFT_ASSOC},
 440   /* DIV */             {15, LEFT_ASSOC},
 441   /* MOD */             {15, LEFT_ASSOC},
 442   /* AND */             {9, LEFT_ASSOC},
 443   /* OR */              {7, LEFT_ASSOC},
 444   /* XOR */             {8, LEFT_ASSOC},
 445   /* RSHIFT */          {13, LEFT_ASSOC},
 446   /* LSHIFT */          {13, LEFT_ASSOC},
 447   /* MIN */             {10, LEFT_ASSOC},       /* C++ specific */
 448   /* MAX */             {10, LEFT_ASSOC},       /* extensions */
 449
 450   /* COMPL */           {16, NO_L_OPERAND},
 451   /* AND_AND */         {6, LEFT_ASSOC},
 452   /* OR_OR */           {5, LEFT_ASSOC},
 453   /* QUERY */           {3, 0},
 454   /* COLON */           {4, LEFT_ASSOC},
 455   /* COMMA */           {2, LEFT_ASSOC},
 456   /* OPEN_PAREN */      {1, NO_L_OPERAND},
 457   /* CLOSE_PAREN */     {0, 0},
 458   /* EOF */             {0, 0},
 459   /* EQ_EQ */           {11, LEFT_ASSOC},
 460   /* NOT_EQ */          {11, LEFT_ASSOC},
 461   /* GREATER_EQ */      {12, LEFT_ASSOC},
 462   /* LESS_EQ */         {12, LEFT_ASSOC},
 463   /* UPLUS */           {16, NO_L_OPERAND},
 464   /* UMINUS */          {16, NO_L_OPERAND}
 465 };
 466
 467 #define COMPARE(OP) \
 468   top->unsignedp = 0; \
 469   top->value = (unsigned1 | unsigned2) \
 470   ? (unsigned HOST_WIDEST_INT) v1 OP (unsigned HOST_WIDEST_INT) v2 \
 471   : (v1 OP v2)
 472 #define EQUALITY(OP) \
 473   top->value = v1 OP v2; \
 474   top->unsignedp = 0;
 475 #define BITWISE(OP) \
 476   top->value = v1 OP v2; \
 477   top->unsignedp = unsigned1 | unsigned2;
 478 #define MINMAX(OP) \
 479   top->value = (v1 OP v2) ? v1 : v2; \
 480   top->unsignedp = unsigned1 | unsigned2;
 481 #define UNARY(OP) \
 482   top->value = OP v2; \
 483   top->unsignedp = unsigned2;
 484 #define SHIFT(PSH, MSH) \
 485   if (pfile->state.skip_eval)  \
 486     break;              \
 487   top->unsignedp = unsigned1; \
 488   if (v2 < 0 && ! unsigned2)  \
 489     top->value = MSH (pfile, v1, unsigned1, -v2); \
 490   else \
 491     top->value = PSH (pfile, v1, unsigned1, v2);
 492
 493 /* Parse and evaluate a C expression, reading from PFILE.
 494    Returns the truth value of the expression.
 495
 496    The implementation is an operator precedence parser, i.e. a
 497    bottom-up parser, using a stack for not-yet-reduced tokens.
 498
 499    The stack base is op_stack, and the current stack pointer is 'top'.
 500    There is a stack element for each operator (only), and the most
 501    recently pushed operator is 'top->op'.  An operand (value) is
 502    stored in the 'value' field of the stack element of the operator
 503    that precedes it.  */
 504 bool
 505 _cpp_parse_expr (pfile)
 506      cpp_reader *pfile;
 507 {
 508   struct op *top = pfile->op_stack;
 509   const cpp_token *token = NULL, *prev_token;
 510   unsigned int lex_count;
 511   bool saw_leading_not, want_value = true;
 512
 513   pfile->state.skip_eval = 0;
 514
 515   /* Set up detection of #if ! defined().  */
 516   pfile->mi_ind_cmacro = 0;
 517   saw_leading_not = false;
 518   lex_count = 0;
 519
 520   /* Lowest priority operator prevents further reductions.  */
 521   top->op = CPP_EOF;
 522
 523   for (;;)
 524     {
 525       struct op op;
 526
 527       prev_token = token;
 528       token = cpp_get_token (pfile);
 529       lex_count++;
 530       op.op = token->type;
 531
 532       switch (op.op)
 533         {
 534           /* These tokens convert into values.  */
 535         case CPP_NUMBER:
 536         case CPP_CHAR:
 537         case CPP_WCHAR:
 538         case CPP_NAME:
 539         case CPP_HASH:
 540           if (!want_value)
 541             SYNTAX_ERROR2 ("missing binary operator before token \"%s\"",
 542                            cpp_token_as_text (pfile, token));
 543           want_value = false;
 544           op = eval_token (pfile, token);
 545           if (op.op == CPP_ERROR)
 546             goto syntax_error;
 547           top->value = op.value;
 548           top->unsignedp = op.unsignedp;
 549           continue;
 550
 551         case CPP_NOT:
 552           saw_leading_not = lex_count == 1;
 553           break;
 554         case CPP_PLUS:
 555           if (want_value)
 556             op.op = CPP_UPLUS;
 557           break;
 558         case CPP_MINUS:
 559           if (want_value)
 560             op.op = CPP_UMINUS;
 561           break;
 562         case CPP_OTHER:
 563           if (ISGRAPH (token->val.c))
 564             SYNTAX_ERROR2 ("invalid character '%c' in #if", token->val.c);
 565           else
 566             SYNTAX_ERROR2 ("invalid character '\\%03o' in #if", token->val.c);
 567
 568         default:
 569           if ((int) op.op <= (int) CPP_EQ || (int) op.op >= (int) CPP_PLUS_EQ)
 570             SYNTAX_ERROR2 ("token \"%s\" is not valid in #if expressions",
 571                            cpp_token_as_text (pfile, token));
 572           break;
 573         }
 574
 575       /* Check we have a value or operator as appropriate.  */
 576       if (optab[op.op].flags & NO_L_OPERAND)
 577         {
 578           if (!want_value)
 579             SYNTAX_ERROR2 ("missing binary operator before token \"%s\"",
 580                            cpp_token_as_text (pfile, token));
 581         }
 582       else if (want_value)
 583         {
 584           /* Ordering here is subtle and intended to favour the
 585              missing parenthesis diagnostics over alternatives.  */
 586           if (op.op == CPP_CLOSE_PAREN)
 587             {
 588               if (top->op == CPP_OPEN_PAREN)
 589                 SYNTAX_ERROR ("void expression between '(' and ')'");
 590             }
 591           else if (top->op == CPP_EOF)
 592             SYNTAX_ERROR ("#if with no expression");
 593           if (top->op != CPP_EOF && top->op != CPP_OPEN_PAREN)
 594             SYNTAX_ERROR2 ("operator '%s' has no right operand",
 595                            cpp_token_as_text (pfile, prev_token));
 596         }
 597
 598       top = reduce (pfile, top, op.op);
 599       if (!top)
 600         goto syntax_error;
 601
 602       if (op.op == CPP_EOF)
 603         break;
 604
 605       switch (op.op)
 606         {
 607         case CPP_CLOSE_PAREN:
 608           continue;
 609         case CPP_OR_OR:
 610           if (top->value)
 611             pfile->state.skip_eval++;
 612           break;
 613         case CPP_AND_AND:
 614         case CPP_QUERY:
 615           if (!top->value)
 616             pfile->state.skip_eval++;
 617           break;
 618         case CPP_COLON:
 619           if (top->op != CPP_QUERY)
 620             SYNTAX_ERROR (" ':' without preceding '?'");
 621           if (top[-1].value) /* Was '?' condition true?  */
 622             pfile->state.skip_eval++;
 623           else
 624             pfile->state.skip_eval--;
 625         default:
 626           break;
 627         }
 628
 629       want_value = true;
 630
 631       /* Check for and handle stack overflow.  */
 632       if (++top == pfile->op_limit)
 633         top = _cpp_expand_op_stack (pfile);
 634
 635       top->op = op.op;
 636     }
 637
 638   /* The controlling macro expression is only valid if we called lex 3
 639      times: <!> <defined expression> and <EOF>.  push_conditional ()
 640      checks that we are at top-of-file.  */
 641   if (pfile->mi_ind_cmacro && !(saw_leading_not && lex_count == 3))
 642     pfile->mi_ind_cmacro = 0;
 643
 644   if (top != pfile->op_stack)
 645     {
 646       cpp_error (pfile, DL_ICE, "unbalanced stack in #if");
 647     syntax_error:
 648       return false;  /* Return false on syntax error.  */
 649     }
 650
 651   return top->value != 0;
 652 }
 653
 654 /* Reduce the operator / value stack if possible, in preparation for
 655    pushing operator OP.  Returns NULL on error, otherwise the top of
 656    the stack.  */
 657 static struct op *
 658 reduce (pfile, top, op)
 659      cpp_reader *pfile;
 660      struct op *top;
 661      enum cpp_ttype op;
 662 {
 663   unsigned int prio;
 664
 665   if (op == CPP_OPEN_PAREN)
 666     return top;
 667
 668   /* Decrement the priority of left-associative operators to force a
 669      reduction with operators of otherwise equal priority.  */
 670   prio = optab[op].prio - ((optab[op].flags & LEFT_ASSOC) != 0);
 671   while (prio < optab[top->op].prio)
 672     {
 673       HOST_WIDEST_INT v1, v2;
 674       unsigned int unsigned1, unsigned2;
 675
 676       unsigned2 = top->unsignedp, v2 = top->value;
 677       top--;
 678       unsigned1 = top->unsignedp, v1 = top->value;
 679
 680       /* Now set top->value = (top[1].op)(v1, v2); */
 681       switch (top[1].op)
 682         {
 683         default:
 684           cpp_error (pfile, DL_ICE, "impossible operator '%u'", top[1].op);
 685           return 0;
 686
 687         case CPP_NOT:    UNARY(!);      break;
 688         case CPP_COMPL:  UNARY(~);      break;
 689         case CPP_LESS:   COMPARE(<);    break;
 690         case CPP_GREATER: COMPARE(>);   break;
 691         case CPP_LESS_EQ: COMPARE(<=);  break;
 692         case CPP_GREATER_EQ: COMPARE(>=); break;
 693         case CPP_EQ_EQ:  EQUALITY(==);  break;
 694         case CPP_NOT_EQ: EQUALITY(!=);  break;
 695         case CPP_AND:    BITWISE(&);    break;
 696         case CPP_XOR:    BITWISE(^);    break;
 697         case CPP_OR:     BITWISE(|);    break;
 698         case CPP_LSHIFT: SHIFT(left_shift, right_shift); break;
 699         case CPP_RSHIFT: SHIFT(right_shift, left_shift); break;
 700         case CPP_MIN:    MINMAX(<);     break;
 701         case CPP_MAX:    MINMAX(>);     break;
 702
 703         case CPP_UPLUS:
 704           /* Can't use UNARY(+) because K+R C did not have unary
 705              plus.  Can't use UNARY() because some compilers object
 706              to the empty argument.  */
 707           top->value = v2;
 708           top->unsignedp = unsigned2;
 709           if (CPP_WTRADITIONAL (pfile))
 710             cpp_error (pfile, DL_WARNING,
 711                        "traditional C rejects the unary plus operator");
 712           break;
 713         case CPP_UMINUS:
 714           UNARY(-);
 715           if (!pfile->state.skip_eval && (top->value & v2) < 0 && !unsigned2)
 716             integer_overflow (pfile);
 717           break;
 718
 719         case CPP_PLUS:
 720           top->value = v1 + v2;
 721           top->unsignedp = unsigned1 | unsigned2;
 722           if (! top->unsignedp && ! pfile->state.skip_eval
 723               && ! possible_sum_sign (v1, v2, top->value))
 724             integer_overflow (pfile);
 725           break;
 726         case CPP_MINUS:
 727           top->value = v1 - v2;
 728           top->unsignedp = unsigned1 | unsigned2;
 729           if (! top->unsignedp && ! pfile->state.skip_eval
 730               && ! possible_sum_sign (top->value, v2, v1))
 731             integer_overflow (pfile);
 732           break;
 733         case CPP_MULT:
 734           top->unsignedp = unsigned1 | unsigned2;
 735           if (top->unsignedp)
 736             top->value = (unsigned HOST_WIDEST_INT) v1 * v2;
 737           else if (!pfile->state.skip_eval)
 738             {
 739               top->value = v1 * v2;
 740               if (v1 && (top->value / v1 != v2
 741                          || (top->value & v1 & v2) < 0))
 742                 integer_overflow (pfile);
 743             }
 744           break;
 745         case CPP_DIV:
 746         case CPP_MOD:
 747           if (pfile->state.skip_eval)
 748             break;
 749           if (v2 == 0)
 750             {
 751               cpp_error (pfile, DL_ERROR, "division by zero in #if");
 752               return 0;
 753             }
 754           top->unsignedp = unsigned1 | unsigned2;
 755           if (top[1].op == CPP_DIV)
 756             {
 757               if (top->unsignedp)
 758                 top->value = (unsigned HOST_WIDEST_INT) v1 / v2;
 759               else
 760                 {
 761                   top->value = v1 / v2;
 762                   if ((top->value & v1 & v2) < 0)
 763                     integer_overflow (pfile);
 764                 }
 765             }
 766           else
 767             {
 768               if (top->unsignedp)
 769                 top->value = (unsigned HOST_WIDEST_INT) v1 % v2;
 770               else
 771                 top->value = v1 % v2;
 772             }
 773           break;
 774
 775         case CPP_OR_OR:
 776           top->value = v1 || v2;
 777           top->unsignedp = 0;
 778           if (v1) pfile->state.skip_eval--;
 779           break;
 780         case CPP_AND_AND:
 781           top->value = v1 && v2;
 782           top->unsignedp = 0;
 783           if (!v1) pfile->state.skip_eval--;
 784           break;
 785         case CPP_COMMA:
 786           if (CPP_PEDANTIC (pfile))
 787             cpp_error (pfile, DL_PEDWARN,
 788                        "comma operator in operand of #if");
 789           top->value = v2;
 790           top->unsignedp = unsigned2;
 791           break;
 792         case CPP_QUERY:
 793           cpp_error (pfile, DL_ERROR, "'?' without following ':'");
 794           return 0;
 795         case CPP_COLON:
 796           top--;
 797           if (top->value) pfile->state.skip_eval--;
 798           top->value = top->value ? v1 : v2;
 799           top->unsignedp = unsigned1 | unsigned2;
 800           break;
 801         case CPP_OPEN_PAREN:
 802           if (op != CPP_CLOSE_PAREN)
 803             {
 804               cpp_error (pfile, DL_ERROR, "missing ')' in expression");
 805               return 0;
 806             }
 807           top->value = v2;
 808           top->unsignedp = unsigned2;
 809           return top;
 810         }
 811     }
 812
 813   if (op == CPP_CLOSE_PAREN)
 814     {
 815       cpp_error (pfile, DL_ERROR, "missing '(' in expression");
 816       return 0;
 817     }
 818
 819   return top;
 820 }
 821
 822 /* Returns the position of the old top of stack after expansion.  */
 823 struct op *
 824 _cpp_expand_op_stack (pfile)
 825      cpp_reader *pfile;
 826 {
 827   size_t n = (size_t) (pfile->op_limit - pfile->op_stack);
 828
 829   pfile->op_stack = (struct op *) xrealloc (pfile->op_stack,
 830                                             (n * 2 + 20) * sizeof (struct op));
 831
 832   return pfile->op_stack + n;
 833 }