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cppexp.c

/* Parse C expressions for CCCP.
 * Copyright (C) 1987, 1992, 1994, 1995 Free Software Foundation.
 * 
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 * 
 * In other words, you are welcome to use, share and improve this program.
 * You are forbidden to forbid anyone else to use, share and improve
 * what you give them.   Help stamp out software-hoarding!
 * 
 * Written by Per Bothner 1994. */

/* Parse a C expression from text in a string  */

#include "config.h"
#include "cpplib.h"
#include "cpphash.h"

#ifdef __EMX__
#include <strings.h>
#endif

#ifdef MULTIBYTE_CHARS
#include <locale.h>
#endif

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

/* This is used for communicating lists of keywords with cccp.c.  */
struct arglist
{
   struct arglist     *next;
   unsigned char      *name;
   int                 length;
   int                 argno;
};

/* Define a generic NULL if one hasn't already been defined.  */

#ifndef NULL
#define NULL 0
#endif

#ifndef GENERIC_PTR
#if defined (USE_PROTOTYPES) ? USE_PROTOTYPES : defined (__STDC__)
#define GENERIC_PTR void *
#else
#define GENERIC_PTR char *
#endif
#endif

#ifndef NULL_PTR
#define NULL_PTR ((GENERIC_PTR)0)
#endif

#ifndef CHAR_TYPE_SIZE
#define CHAR_TYPE_SIZE BITS_PER_UNIT
#endif

#ifndef INT_TYPE_SIZE
#define INT_TYPE_SIZE BITS_PER_WORD
#endif

#ifndef LONG_TYPE_SIZE
#define LONG_TYPE_SIZE BITS_PER_WORD
#endif

#ifndef WCHAR_TYPE_SIZE
#define WCHAR_TYPE_SIZE INT_TYPE_SIZE
#endif

#ifndef MAX_CHAR_TYPE_SIZE
#define MAX_CHAR_TYPE_SIZE CHAR_TYPE_SIZE
#endif

#ifndef MAX_INT_TYPE_SIZE
#define MAX_INT_TYPE_SIZE INT_TYPE_SIZE
#endif

#ifndef MAX_LONG_TYPE_SIZE
#define MAX_LONG_TYPE_SIZE LONG_TYPE_SIZE
#endif

#ifndef MAX_WCHAR_TYPE_SIZE
#define MAX_WCHAR_TYPE_SIZE WCHAR_TYPE_SIZE
#endif

/* Yield nonzero if adding two numbers with A's and B's signs can yield a
 * number with SUM's sign, where A, B, and SUM are all C integers.  */
#define possible_sum_sign(a, b, sum) ((((a) ^ (b)) | ~ ((a) ^ (sum))) < 0)

#define ERROR 299
#define OROR 300
#define ANDAND 301
#define EQUAL 302
#define NOTEQUAL 303
#define LEQ 304
#define GEQ 305
#define LSH 306
#define RSH 307
#define NAME 308
#define INT 309
#define CHAR 310

#define LEFT_OPERAND_REQUIRED 1
#define RIGHT_OPERAND_REQUIRED 2
#define HAVE_VALUE 4
/* SKIP_OPERAND is set for '&&' '||' '?' and ':' when the
 * following operand should be short-circuited instead of evaluated. */
#define SKIP_OPERAND 8
/*#define UNSIGNEDP 16 */

struct operation
{
   short               op;
   char                rprio; /* Priority of op (relative to it right operand). */
   char                flags;
   char                unsignedp;   /* true if value should be treated as unsigned */
   HOST_WIDE_INT       value; /* The value logically "right" of op. */
};

/* Take care of parsing a number (anything that starts with a digit).
 * LEN is the number of characters in it.  */

/* maybe needs to actually deal with floating point numbers */

static void
parse_number(struct operation *op, cpp_reader * pfile, const char *start,
           int olen)
{
   const char         *p = start;
   int                 c;
   unsigned long       n = 0, nd, ULONG_MAX_over_base;
   int                 base = 10;
   int                 len = olen;
   int                 overflow = 0;
   int                 digit, largest_digit = 0;
   int                 spec_long = 0;

   op->unsignedp = 0;

   for (c = 0; c < len; c++)
      if (p[c] == '.')
      {
         /* It's a float since it contains a point.  */
         cpp_error(pfile,
                 "floating point numbers not allowed in #if expressions");
         op->op = ERROR;
         return;
      }
   if (len >= 3 && (!strncmp(p, "0x", 2) || !strncmp(p, "0X", 2)))
     {
      p += 2;
      base = 16;
      len -= 2;
     }
   else if (*p == '0')
      base = 8;

   /* Some buggy compilers (e.g. MPW C) seem to need both casts. */
   ULONG_MAX_over_base = ((unsigned long)-1) / ((unsigned long)base);

   for (; len > 0; len--)
     {
      c = *p++;

      if (c >= '0' && c <= '9')
         digit = c - '0';
      else if (base == 16 && c >= 'a' && c <= 'f')
         digit = c - 'a' + 10;
      else if (base == 16 && c >= 'A' && c <= 'F')
         digit = c - 'A' + 10;
      else
        {
           /* `l' means long, and `u' means unsigned.  */
           while (1)
             {
              if (c == 'l' || c == 'L')
                {
                   if (spec_long)
                    cpp_error(pfile, "two `l's in integer constant");
                   spec_long = 1;
                }
              else if (c == 'u' || c == 'U')
                {
                   if (op->unsignedp)
                    cpp_error(pfile, "two `u's in integer constant");
                   op->unsignedp = 1;
                }
              else
                 break;

              if (--len == 0)
                 break;
              c = *p++;
             }
           /* Don't look for any more digits after the suffixes.  */
           break;
        }
      if (largest_digit < digit)
         largest_digit = digit;
      nd = n * base + digit;
      overflow |= (ULONG_MAX_over_base < n) | (nd < n);
      n = nd;
     }

   if (len != 0)
     {
      cpp_error(pfile, "Invalid number in #if expression");
      op->op = ERROR;
      return;
     }
   if (base <= largest_digit)
      cpp_warning(pfile, "integer constant contains digits beyond the radix");

   if (overflow)
      cpp_warning(pfile, "integer constant out of range");

   /* If too big to be signed, consider it unsigned.  */
   if ((long)n < 0 && !op->unsignedp)
     {
      if (base == 10)
         cpp_warning(pfile,
                   "integer constant is so large that it is unsigned");
      op->unsignedp = 1;
     }
   op->value = n;
   op->op = INT;
}

struct token
{
   const char         *oper;
   int                 token;
};

static struct token tokentab2[] = {
   {"&&", ANDAND},
   {"||", OROR},
   {"<<", LSH},
   {">>", RSH},
   {"==", EQUAL},
   {"!=", NOTEQUAL},
   {"<=", LEQ},
   {">=", GEQ},
   {"++", ERROR},
   {"--", ERROR},
   {NULL, ERROR}
};

/* Read one token. */

static void
cpp_lex(struct operation *op, cpp_reader * pfile)
{
   int                 c;
   struct token       *toktab;
   enum cpp_token      token;
   unsigned char      *tok_start, *tok_end;
   int                 old_written;

   op->value = 0;
   op->unsignedp = 0;

 retry:

   old_written = CPP_WRITTEN(pfile);
   cpp_skip_hspace(pfile);
   c = CPP_BUF_PEEK(CPP_BUFFER(pfile));
   if (c == '#')
     {
      parse_number(op, pfile, cpp_read_check_assertion(pfile) ? "1" : "0", 1);
      return;
     }

   if (c == '\n')
     {
      op->op = 0;
      return;
     }
   token = cpp_get_token(pfile);
   tok_start = pfile->token_buffer + old_written;
   tok_end = CPP_PWRITTEN(pfile);
   pfile->limit = tok_start;
   switch (token)
     {
     case CPP_EOF:            /* Should not happen ... */
      op->op = 0;
      break;

     case CPP_VSPACE:
     case CPP_POP:
      if (CPP_BUFFER(pfile)->fname != NULL)
        {
           op->op = 0;
           break;
        }
      goto retry;

     case CPP_HSPACE:
     case CPP_COMMENT:
      goto retry;

     case CPP_NUMBER:
      parse_number(op, pfile, (char *)tok_start, tok_end - tok_start);
      break;

     case CPP_STRING:
      cpp_error(pfile, "string constants not allowed in #if expressions");
      op->op = ERROR;
      break;

     case CPP_CHAR:
      /* This code for reading a character constant
       * handles multicharacter constants and wide characters.
       * It is mostly copied from c-lex.c.  */
      {
         int                 result = 0;
         int                 num_chars = 0;
         unsigned            width = MAX_CHAR_TYPE_SIZE;
         int                 wide_flag = 0;
         int                 max_chars;
         char               *ptr = (char *)tok_start;

#ifdef MULTIBYTE_CHARS
         char                token_buffer[MAX_LONG_TYPE_SIZE /
                                  MAX_CHAR_TYPE_SIZE + MB_CUR_MAX];

#else
         char                token_buffer[MAX_LONG_TYPE_SIZE /
                                  MAX_CHAR_TYPE_SIZE + 1];

#endif

         if (*ptr == 'L')
           {
            ptr++;
            wide_flag = 1;
            width = MAX_WCHAR_TYPE_SIZE;
#ifdef MULTIBYTE_CHARS
            max_chars = MB_CUR_MAX;
#else
            max_chars = 1;
#endif
           }
         else
            max_chars = MAX_LONG_TYPE_SIZE / width;

         while (1)
           {
            if (ptr >= (char *)CPP_PWRITTEN(pfile) || (c = *ptr++) == '\'')
               break;

            if (c == '\\')
              {
                 c = cpp_parse_escape(pfile, &ptr);
                 if (width < HOST_BITS_PER_INT
                   && (unsigned)c >= (unsigned)(1 << width))
                  cpp_pedwarn(pfile,
                            "escape sequence out of range for character");
              }
            num_chars++;

            /* Merge character into result; ignore excess chars.  */
            if (num_chars < max_chars + 1)
              {
                 if (width < HOST_BITS_PER_INT)
                  result = (result << width) | (c & ((1 << width) - 1));
                 else
                  result = c;
                 token_buffer[num_chars - 1] = c;
              }
           }

         token_buffer[num_chars] = 0;

         if (c != '\'')
            cpp_error(pfile, "malformatted character constant");
         else if (num_chars == 0)
            cpp_error(pfile, "empty character constant");
         else if (num_chars > max_chars)
           {
            num_chars = max_chars;
            cpp_error(pfile, "character constant too long");
           }
         else if (num_chars != 1 && !CPP_TRADITIONAL(pfile))
            cpp_warning(pfile, "multi-character character constant");

         /* If char type is signed, sign-extend the constant.  */
         if (!wide_flag)
           {
            int                 num_bits = num_chars * width;

            if (cpp_lookup("__CHAR_UNSIGNED__",
                         sizeof("__CHAR_UNSIGNED__") - 1, -1)
                || ((result >> (num_bits - 1)) & 1) == 0)
               op->value =
                  result & ((unsigned long)~0 >>
                        (HOST_BITS_PER_LONG - num_bits));
            else
               op->value =
                  result | ~((unsigned long)~0 >>
                         (HOST_BITS_PER_LONG - num_bits));
           }
         else
           {
#ifdef MULTIBYTE_CHARS
            /* Set the initial shift state and convert the next sequence.  */
            result = 0;
            /* In all locales L'\0' is zero and mbtowc will return zero,
             * so don't use it.  */
            if (num_chars > 1
                || (num_chars == 1 && token_buffer[0] != '\0'))
              {
                 wchar_t             wc;

                 (void)mbtowc(NULL_PTR, NULL_PTR, 0);
                 if (mbtowc(&wc, token_buffer, num_chars) == num_chars)
                  result = wc;
                 else
                  cpp_warning(pfile,
                            "Ignoring invalid multibyte character");
              }
#endif
            op->value = result;
           }
      }

      /* This is always a signed type.  */
      op->unsignedp = 0;
      op->op = CHAR;
      break;

     case CPP_NAME:
      parse_number(op, pfile, "0", 0);
      break;

     case CPP_OTHER:
      /* See if it is a special token of length 2.  */
      if (tok_start + 2 == tok_end)
        {
           for (toktab = tokentab2; toktab->oper != NULL; toktab++)
            if (tok_start[0] == toktab->oper[0]
                && tok_start[1] == toktab->oper[1])
               break;
           if (toktab->token == ERROR)
             {
              char               *buf = (char *)malloc(40);

              memset(buf, 0, 40);

              sprintf(buf, "`%s' not allowed in operand of `#if'",
                    tok_start);
              cpp_error(pfile, buf);
              free(buf);
             }
           op->op = toktab->token;
           break;
        }
      /* fall through */
     default:
      op->op = *tok_start;
      break;
     }
}

/* Parse a C escape sequence.  STRING_PTR points to a variable
 * containing a pointer to the string to parse.  That pointer
 * is updated past the characters we use.  The value of the
 * escape sequence is returned.
 * 
 * A negative value means the sequence \ newline was seen,
 * which is supposed to be equivalent to nothing at all.
 * 
 * If \ is followed by a null character, we return a negative
 * value and leave the string pointer pointing at the null character.
 * 
 * If \ is followed by 000, we return 0 and leave the string pointer
 * after the zeros.  A value of 0 does not mean end of string.  */

int
cpp_parse_escape(cpp_reader * pfile, char **string_ptr)
{
   int                 c = *(*string_ptr)++;

   switch (c)
     {
     case 'a':
      return TARGET_BELL;
     case 'b':
      return TARGET_BS;
     case 'e':
     case 'E':
      if (CPP_PEDANTIC(pfile))
         cpp_pedwarn(pfile, "non-ANSI-standard escape sequence, `\\%c'", c);
      return 033;
     case 'f':
      return TARGET_FF;
     case 'n':
      return TARGET_NEWLINE;
     case 'r':
      return TARGET_CR;
     case 't':
      return TARGET_TAB;
     case 'v':
      return TARGET_VT;
     case '\n':
      return -2;
     case 0:
      (*string_ptr)--;
      return 0;

     case '0':
     case '1':
     case '2':
     case '3':
     case '4':
     case '5':
     case '6':
     case '7':
      {
         int                 i = c - '0';
         int                 count = 0;

         while (++count < 3)
           {
            c = *(*string_ptr)++;
            if (c >= '0' && c <= '7')
               i = (i << 3) + c - '0';
            else
              {
                 (*string_ptr)--;
                 break;
              }
           }
         if ((i & ~((1 << MAX_CHAR_TYPE_SIZE) - 1)) != 0)
           {
            i &= (1 << MAX_CHAR_TYPE_SIZE) - 1;
            cpp_warning(pfile,
                      "octal character constant does not fit in a byte");
           }
         return i;
      }
     case 'x':
      {
         unsigned            i = 0, overflow = 0, digits_found = 0, digit;

         for (;;)
           {
            c = *(*string_ptr)++;
            if (c >= '0' && c <= '9')
               digit = c - '0';
            else if (c >= 'a' && c <= 'f')
               digit = c - 'a' + 10;
            else if (c >= 'A' && c <= 'F')
               digit = c - 'A' + 10;
            else
              {
                 (*string_ptr)--;
                 break;
              }
            overflow |= i ^ (i << 4 >> 4);
            i = (i << 4) + digit;
            digits_found = 1;
           }
         if (!digits_found)
            cpp_error(pfile, "\\x used with no following hex digits");
         if (overflow | (i & ~((1 << BITS_PER_UNIT) - 1)))
           {
            i &= (1 << BITS_PER_UNIT) - 1;
            cpp_warning(pfile,
                      "hex character constant does not fit in a byte");
           }
         return i;
      }
     default:
      return c;
     }
}

static void
integer_overflow(cpp_reader * pfile)
{
   if (CPP_PEDANTIC(pfile))
      cpp_pedwarn(pfile, "integer overflow in preprocessor expression");
}

static long
left_shift(cpp_reader * pfile, long a, int unsignedp, unsigned long b)
{
   if (b >= HOST_BITS_PER_LONG)
     {
      if (!unsignedp && a != 0)
         integer_overflow(pfile);
      return 0;
     }
   else if (unsignedp)
      return (unsigned long)a << b;
   else
     {
      long                l = a << b;

      if (l >> b != a)
         integer_overflow(pfile);
      return l;
     }
}

static long
right_shift(cpp_reader * pfile, long a, int unsignedp, unsigned long b)
{
   pfile = NULL;
   if (b >= HOST_BITS_PER_LONG)
     {
      return unsignedp ? 0 : a >> (HOST_BITS_PER_LONG - 1);
     }
   else if (unsignedp)
     {
      return (unsigned long)a >> b;
     }
   else
     {
      return a >> b;
     }
}

/* These priorities are all even, so we can handle associatively. */
#define PAREN_INNER_PRIO 0
#define COMMA_PRIO 4
#define COND_PRIO (COMMA_PRIO+2)
#define OROR_PRIO (COND_PRIO+2)
#define ANDAND_PRIO (OROR_PRIO+2)
#define OR_PRIO (ANDAND_PRIO+2)
#define XOR_PRIO (OR_PRIO+2)
#define AND_PRIO (XOR_PRIO+2)
#define EQUAL_PRIO (AND_PRIO+2)
#define LESS_PRIO (EQUAL_PRIO+2)
#define SHIFT_PRIO (LESS_PRIO+2)
#define PLUS_PRIO (SHIFT_PRIO+2)
#define MUL_PRIO (PLUS_PRIO+2)
#define UNARY_PRIO (MUL_PRIO+2)
#define PAREN_OUTER_PRIO (UNARY_PRIO+2)

#define COMPARE(OP) \
  top->unsignedp = 0;\
  top->value = (unsigned1 || unsigned2) ? (unsigned long) v1 OP (unsigned long) v2 : (v1 OP v2)

/* Parse and evaluate a C expression, reading from PFILE.
 * Returns the value of the expression.  */

HOST_WIDE_INT
cpp_parse_expr(cpp_reader * pfile)
{
   /* The implementation is an operator precedence parser,
    * i.e. a bottom-up parser, using a stack for not-yet-reduced tokens.
    * 
    * The stack base is 'stack', and the current stack pointer is 'top'.
    * There is a stack element for each operator (only),
    * and the most recently pushed operator is 'top->op'.
    * An operand (value) is stored in the 'value' field of the stack
    * element of the operator that precedes it.
    * In that case the 'flags' field has the HAVE_VALUE flag set.  */

#define INIT_STACK_SIZE 20
   struct operation    init_stack[INIT_STACK_SIZE];
   struct operation   *stack = init_stack;
   struct operation   *limit = stack + INIT_STACK_SIZE;
   struct operation   *top = stack;
   int                 lprio = 0, rprio = 0;
   int                 skip_evaluation = 0;

   top->rprio = 0;
   top->flags = 0;
   for (;;)
     {
      struct operation    op;
      char                flags = 0;

      /* Read a token */
      cpp_lex(&op, pfile);

      /* See if the token is an operand, in which case go to set_value.
       * If the token is an operator, figure out its left and right
       * priorities, and then goto maybe_reduce. */

      switch (op.op)
        {
        case NAME:
           top->value = 0, top->unsignedp = 0;
           goto set_value;
        case INT:
        case CHAR:
           top->value = op.value;
           top->unsignedp = op.unsignedp;
           goto set_value;
        case 0:
           lprio = 0;
           goto maybe_reduce;
        case '+':
        case '-':
           /* Is this correct if unary ? FIXME */
           flags = RIGHT_OPERAND_REQUIRED;
           lprio = PLUS_PRIO;
           rprio = lprio + 1;
           goto maybe_reduce;
        case '!':
        case '~':
           flags = RIGHT_OPERAND_REQUIRED;
           rprio = UNARY_PRIO;
           lprio = rprio + 1;
           goto maybe_reduce;
        case '*':
        case '/':
        case '%':
           lprio = MUL_PRIO;
           goto binop;
        case '<':
        case '>':
        case LEQ:
        case GEQ:
           lprio = LESS_PRIO;
           goto binop;
        case EQUAL:
        case NOTEQUAL:
           lprio = EQUAL_PRIO;
           goto binop;
        case LSH:
        case RSH:
           lprio = SHIFT_PRIO;
           goto binop;
        case '&':
           lprio = AND_PRIO;
           goto binop;
        case '^':
           lprio = XOR_PRIO;
           goto binop;
        case '|':
           lprio = OR_PRIO;
           goto binop;
        case ANDAND:
           lprio = ANDAND_PRIO;
           goto binop;
        case OROR:
           lprio = OROR_PRIO;
           goto binop;
        case ',':
           lprio = COMMA_PRIO;
           goto binop;
        case '(':
           lprio = PAREN_OUTER_PRIO;
           rprio = PAREN_INNER_PRIO;
           goto maybe_reduce;
        case ')':
           lprio = PAREN_INNER_PRIO;
           rprio = PAREN_OUTER_PRIO;
           goto maybe_reduce;
        case ':':
           lprio = COND_PRIO;
           rprio = COND_PRIO;
           goto maybe_reduce;
        case '?':
           lprio = COND_PRIO + 1;
           rprio = COND_PRIO;
           goto maybe_reduce;
         binop:
           flags = LEFT_OPERAND_REQUIRED | RIGHT_OPERAND_REQUIRED;
           rprio = lprio + 1;
           goto maybe_reduce;
        default:
           cpp_error(pfile, "invalid character in #if");
           goto syntax_error;
        }

      set_value:
      /* Push a value onto the stack. */
      if (top->flags & HAVE_VALUE)
        {
           cpp_error(pfile, "syntax error in #if");
           goto syntax_error;
        }
      top->flags |= HAVE_VALUE;
      continue;

      maybe_reduce:
      /* Push an operator, and check if we can reduce now. */
      while (top->rprio > lprio)
        {
           long                v1 = top[-1].value, v2 = top[0].value;
           int                 unsigned1 = top[-1].unsignedp, unsigned2 =
            top[0].unsignedp;

           top--;
           if ((top[1].flags & LEFT_OPERAND_REQUIRED)
             && !(top[0].flags & HAVE_VALUE))
             {
              cpp_error(pfile, "syntax error - missing left operand");
              goto syntax_error;
             }
           if ((top[1].flags & RIGHT_OPERAND_REQUIRED)
             && !(top[1].flags & HAVE_VALUE))
             {
              cpp_error(pfile, "syntax error - missing right operand");
              goto syntax_error;
             }
           /* top[0].value = (top[1].op)(v1, v2); */
           switch (top[1].op)
             {
             case '+':
              if (!(top->flags & HAVE_VALUE))
                {       /* Unary '+' */
                   top->value = v2;
                   top->unsignedp = unsigned2;
                   top->flags |= HAVE_VALUE;
                }
              else
                {
                   top->value = v1 + v2;
                   top->unsignedp = unsigned1 || unsigned2;
                   if (!top->unsignedp && !skip_evaluation
                     && !possible_sum_sign(v1, v2, top->value))
                    integer_overflow(pfile);
                }
              break;
             case '-':
              if (skip_evaluation); /* do nothing */
              else if (!(top->flags & HAVE_VALUE))
                {       /* Unary '-' */
                   top->value = -v2;
                   if ((top->value & v2) < 0 && !unsigned2)
                    integer_overflow(pfile);
                   top->unsignedp = unsigned2;
                   top->flags |= HAVE_VALUE;
                }
              else
                {       /* Binary '-' */
                   top->value = v1 - v2;
                   top->unsignedp = unsigned1 || unsigned2;
                   if (!top->unsignedp
                     && !possible_sum_sign(top->value, v2, v1))
                    integer_overflow(pfile);
                }
              break;
             case '*':
              top->unsignedp = unsigned1 || unsigned2;
              if (top->unsignedp)
                 top->value = (unsigned long)v1 *v2;

              else if (!skip_evaluation)
                {
                   top->value = v1 * v2;
                   if (v1
                     && (top->value / v1 != v2
                         || (top->value & v1 & v2) < 0))
                    integer_overflow(pfile);
                }
              break;
             case '/':
              if (skip_evaluation)
                 break;
              if (v2 == 0)
                {
                   cpp_error(pfile, "division by zero in #if");
                   v2 = 1;
                }
              top->unsignedp = unsigned1 || unsigned2;
              if (top->unsignedp)
                 top->value = (unsigned long)v1 / v2;
              else
                {
                   top->value = v1 / v2;
                   if ((top->value & v1 & v2) < 0)
                    integer_overflow(pfile);
                }
              break;
             case '%':
              if (skip_evaluation)
                 break;
              if (v2 == 0)
                {
                   cpp_error(pfile, "division by zero in #if");
                   v2 = 1;
                }
              top->unsignedp = unsigned1 || unsigned2;
              if (top->unsignedp)
                 top->value = (unsigned long)v1 % v2;
              else
                 top->value = v1 % v2;
              break;
             case '!':
              if (top->flags & HAVE_VALUE)
                {
                   cpp_error(pfile, "syntax error");
                   goto syntax_error;
                }
              top->value = !v2;
              top->unsignedp = 0;
              top->flags |= HAVE_VALUE;
              break;
             case '~':
              if (top->flags & HAVE_VALUE)
                {
                   cpp_error(pfile, "syntax error");
                   goto syntax_error;
                }
              top->value = ~v2;
              top->unsignedp = unsigned2;
              top->flags |= HAVE_VALUE;
              break;
             case '<':
              COMPARE(<);
              break;
             case '>':
              COMPARE(>);
              break;
             case LEQ:
              COMPARE(<=);
              break;
             case GEQ:
              COMPARE(>=);
              break;
             case EQUAL:
              top->value = (v1 == v2);
              top->unsignedp = 0;
              break;
             case NOTEQUAL:
              top->value = (v1 != v2);
              top->unsignedp = 0;
              break;
             case LSH:
              if (skip_evaluation)
                 break;
              top->unsignedp = unsigned1;
              if (v2 < 0 && !unsigned2)
                 top->value = right_shift(pfile, v1, unsigned1, -v2);
              else
                 top->value = left_shift(pfile, v1, unsigned1, v2);
              break;
             case RSH:
              if (skip_evaluation)
                 break;
              top->unsignedp = unsigned1;
              if (v2 < 0 && !unsigned2)
                 top->value = left_shift(pfile, v1, unsigned1, -v2);
              else
                 top->value = right_shift(pfile, v1, unsigned1, v2);
              break;
#define LOGICAL(OP) \
            top->value = v1 OP v2;\
            top->unsignedp = unsigned1 || unsigned2;
             case '&':
              LOGICAL(&);
              break;
             case '^':
              LOGICAL(^);
              break;
             case '|':
              LOGICAL(|);
              break;
             case ANDAND:
              top->value = v1 && v2;
              top->unsignedp = 0;
              if (!v1)
                 skip_evaluation--;
              break;
             case OROR:
              top->value = v1 || v2;
              top->unsignedp = 0;
              if (v1)
                 skip_evaluation--;
              break;
             case ',':
              if (CPP_PEDANTIC(pfile))
                 cpp_pedwarn(pfile, "comma operator in operand of `#if'");
              top->value = v2;
              top->unsignedp = unsigned2;
              break;
             case '(':
             case '?':
              cpp_error(pfile, "syntax error in #if");
              goto syntax_error;
             case ':':
              if (top[0].op != '?')
                {
                   cpp_error(pfile,
                         "syntax error ':' without preceding '?'");
                   goto syntax_error;
                }
              else if (!(top[1].flags & HAVE_VALUE)
                     || !(top[-1].flags & HAVE_VALUE)
                     || !(top[0].flags & HAVE_VALUE))
                {
                   cpp_error(pfile, "bad syntax for ?: operator");
                   goto syntax_error;
                }
              else
                {
                   top--;
                   if (top->value)
                    skip_evaluation--;
                   top->value = top->value ? v1 : v2;
                   top->unsignedp = unsigned1 || unsigned2;
                }
              break;
             case ')':
              if ((top[1].flags & HAVE_VALUE)
                  || !(top[0].flags & HAVE_VALUE)
                  || top[0].op != '(' || (top[-1].flags & HAVE_VALUE))
                {
                   cpp_error(pfile, "mismatched parentheses in #if");
                   goto syntax_error;
                }
              else
                {
                   top--;
                   top->value = v1;
                   top->unsignedp = unsigned1;
                   top->flags |= HAVE_VALUE;
                }
              break;
             default:
              fprintf(stderr,
                    top[1].op >= ' ' && top[1].op <= '~'
                    ? "unimplemented operator '%c'\n"
                    : "unimplemented operator '\\%03o'\n", top[1].op);
             }
        }
      if (op.op == 0)
        {
           if (top != stack)
            cpp_error(pfile, "internal error in #if expression");
           if (stack != init_stack)
            free(stack);
           return top->value;
        }
      top++;

      /* Check for and handle stack overflow. */
      if (top == limit)
        {
           struct operation   *new_stack;
           int                 old_size = (char *)limit - (char *)stack;
           int                 new_size = 2 * old_size;

           if (stack != init_stack)
            new_stack = (struct operation *)xrealloc(stack, new_size);
           else
             {
              new_stack = (struct operation *)xmalloc(new_size);
              memcpy((char *)new_stack, (char *)stack, old_size);
             }
           stack = new_stack;
           top = (struct operation *)((char *)new_stack + old_size);
           limit = (struct operation *)((char *)new_stack + new_size);
        }
      top->flags = flags;
      top->rprio = rprio;
      top->op = op.op;
      if ((op.op == OROR && top[-1].value)
          || (op.op == ANDAND && !top[-1].value)
          || (op.op == '?' && !top[-1].value))
        {
           skip_evaluation++;
        }
      else if (op.op == ':')
        {
           if (top[-2].value) /* Was condition true? */
            skip_evaluation++;
           else
            skip_evaluation--;
        }
     }
 syntax_error:
   if (stack != init_stack)
      free(stack);
   skip_rest_of_line(pfile);
   return 0;
}

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