gas/cond.c

   1 /* cond.c - conditional assembly pseudo-ops, and .include
   2    Copyright (C) 1990, 1991 Free Software Foundation, Inc.
   3
   4 This file is part of GAS, the GNU Assembler.
   5
   6 GAS is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 1, or (at your option)
   9 any later version.
  10
  11 GAS 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 GAS; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /* static const char rcsid[] = "$Id$"; */
  21
  22 #include "as.h"
  23
  24 #include "obstack.h"
  25
  26 void s_ifdef(arg)
  27 int arg;
  28 {
  29 /*      register char c; */
  30         register char *name;    /* points to name of symbol */
  31         register struct symbol *        symbolP; /* Points to symbol */
  32
  33         SKIP_WHITESPACE();              /* Leading whitespace is part of operand. */
  34         name = input_line_pointer;
  35         if (!is_name_beginner(*name)) {
  36                 as_bad("invalid identifier for .ifdef");
  37                 obstack_1grow (&cond_obstack, 0);
  38         } else {
  39                 get_symbol_end();
  40                 ++input_line_pointer;
  41                 symbolP = symbol_find(name);
  42
  43                 /* ??? Should we try to optimize such that if we hit a .endif
  44                    before a .else, we don't need to push state?  */
  45                 obstack_1grow(&cond_obstack, (symbolP != 0) ^ arg);
  46         }
  47 } /* s_ifdef() */
  48
  49 /* This is allocated to grow and shrink as .ifdef/.endif pairs
  50    are scanned.  When the top element is nonzero, it means
  51    we should accept input.  Otherwise, we should ignore input.  */
  52 struct obstack cond_obstack;
  53
  54 void s_if(arg)
  55 int arg;
  56 {
  57         expressionS operand;
  58
  59         SKIP_WHITESPACE();              /* Leading whitespace is part of operand. */
  60         expr(0, &operand);
  61
  62         if (operand.X_add_symbol != NULL
  63             || operand.X_subtract_symbol != NULL)
  64             as_bad("non-constant expression in .if statement");
  65
  66         /* If the above error is signaled, this will dispatch
  67            using an undefined result.  No big deal.  */
  68         obstack_1grow(&cond_obstack, (operand.X_add_number != 0) ^ arg);
  69 } /* s_if() */
  70
  71 void s_endif(arg)
  72 int arg;
  73 {
  74         char *base = obstack_base(&cond_obstack);
  75         char *ptr = obstack_next_free(&cond_obstack);
  76
  77         if (ptr-1 == base) {
  78                 as_bad("unbalanced .endif");
  79         } else {
  80                 obstack_free(&cond_obstack, ptr-1);
  81                 cond_obstack.object_base = base;
  82         }
  83 } /* s_endif() */
  84
  85 void s_else(arg)
  86 int arg;
  87 {
  88         char *ptr = obstack_next_free(&cond_obstack);
  89         if (ptr-1 == obstack_base(&cond_obstack)) {
  90                 as_bad(".else without matching .if");
  91         } else {
  92                 ptr[-1] = !ptr[-1];
  93         }
  94 } /* s_else() */
  95
  96 void s_ifeqs(arg)
  97 int arg;
  98 {
  99         as_bad("ifeqs not implemented.");
 100 } /* s_ifeqs() */
 101
 102 void s_end(arg)
 103 int arg;
 104 {
 105         ;
 106 } /* s_end() */
 107
 108 int ignore_input() {
 109   char *ptr = obstack_next_free (&cond_obstack);
 110
 111   /* We cannot ignore certain pseudo ops.  */
 112   if (input_line_pointer[-1] == '.')
 113     {
 114       if (input_line_pointer[0] == 'i'
 115           && (!strncmp (input_line_pointer, "if", 2)
 116               || !strncmp (input_line_pointer, "ifdef", 5)
 117               || !strncmp (input_line_pointer, "ifndef", 6)))
 118         return 0;
 119       if (input_line_pointer[0] == 'e'
 120           && (!strncmp (input_line_pointer, "else", 4)
 121               || !strncmp (input_line_pointer, "endif", 5)))
 122         return 0;
 123     }
 124
 125   return (ptr[-1] == 0);
 126 } /* ignore_input() */
 127
 128 /* end of cond.c */