gcc/c-pragma.c

   1 /* Handle #pragma, system V.4 style.  Supports #pragma weak and #pragma pack.
   2    Copyright (C) 1992, 1997, 1998, 1999, 2000, 2001
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 2, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to the Free
  19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, USA.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "rtl.h"
  25 #include "tree.h"
  26 #include "function.h"
  27 #include "cpplib.h"
  28 #include "c-pragma.h"
  29 #include "flags.h"
  30 #include "toplev.h"
  31 #include "ggc.h"
  32 #include "c-lex.h"
  33 #include "output.h"
  34 #include "tm_p.h"
  35
  36 #define BAD(msgid) do { warning (msgid); return; } while (0)
  37 #define BAD2(msgid, arg) do { warning (msgid, arg); return; } while (0)
  38
  39 #ifdef HANDLE_PRAGMA_PACK
  40 static void handle_pragma_pack PARAMS ((cpp_reader *));
  41
  42 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
  43 typedef struct align_stack
  44 {
  45   int                  alignment;
  46   unsigned int         num_pushes;
  47   tree                 id;
  48   struct align_stack * prev;
  49 } align_stack;
  50
  51 static struct align_stack * alignment_stack = NULL;
  52
  53 /* If we have a "global" #pragma pack(<n>) in effect when the first
  54    #pragma pack(push,<n>) is encountered, this stores the value of
  55    maximum_field_alignment in effect.  When the final pop_alignment()
  56    happens, we restore the value to this, not to a value of 0 for
  57    maximum_field_alignment.  Value is in bits.  */
  58 static int  default_alignment;
  59 #define SET_GLOBAL_ALIGNMENT(ALIGN) \
  60 (default_alignment = maximum_field_alignment = (ALIGN))
  61
  62 static void push_alignment PARAMS ((int, tree));
  63 static void pop_alignment  PARAMS ((tree));
  64 static void mark_align_stack PARAMS ((void *));
  65
  66 /* Push an alignment value onto the stack.  */
  67 static void
  68 push_alignment (alignment, id)
  69      int alignment;
  70      tree id;
  71 {
  72
  73   if (alignment_stack == NULL
  74       || alignment_stack->alignment != alignment
  75       || id != NULL_TREE)
  76     {
  77       align_stack * entry;
  78
  79       entry = (align_stack *) xmalloc (sizeof (* entry));
  80
  81       entry->alignment  = alignment;
  82       entry->num_pushes = 1;
  83       entry->id         = id;
  84       entry->prev       = alignment_stack;
  85
  86       /* The current value of maximum_field_alignment is not necessarily
  87          0 since there may be a #pragma pack(<n>) in effect; remember it
  88          so that we can restore it after the final #pragma pop().  */
  89       if (alignment_stack == NULL)
  90         default_alignment = maximum_field_alignment;
  91
  92       alignment_stack = entry;
  93
  94       maximum_field_alignment = alignment;
  95     }
  96   else
  97     alignment_stack->num_pushes ++;
  98 }
  99
 100 /* Undo a push of an alignment onto the stack.  */
 101 static void
 102 pop_alignment (id)
 103      tree id;
 104 {
 105   align_stack * entry;
 106
 107   if (alignment_stack == NULL)
 108     {
 109       warning ("\
 110 #pragma pack (pop) encountered without matching #pragma pack (push, <n>)"
 111                );
 112       return;
 113     }
 114
 115   /* If we got an identifier, strip away everything above the target
 116      entry so that the next step will restore the state just below it.  */
 117   if (id)
 118     {
 119       for (entry = alignment_stack; entry; entry = entry->prev)
 120         if (entry->id == id)
 121           {
 122             entry->num_pushes = 1;
 123             alignment_stack = entry;
 124             break;
 125           }
 126       if (entry == NULL)
 127         warning ("\
 128 #pragma pack(pop, %s) encountered without matching #pragma pack(push, %s, <n>)"
 129                  , IDENTIFIER_POINTER (id), IDENTIFIER_POINTER (id));
 130     }
 131
 132   if (-- alignment_stack->num_pushes == 0)
 133     {
 134       entry = alignment_stack->prev;
 135
 136       if (entry == NULL)
 137         maximum_field_alignment = default_alignment;
 138       else
 139         maximum_field_alignment = entry->alignment;
 140
 141       free (alignment_stack);
 142
 143       alignment_stack = entry;
 144     }
 145 }
 146
 147 static void
 148 mark_align_stack (p)
 149     void *p;
 150 {
 151   align_stack *a = *(align_stack **) p;
 152
 153   while (a)
 154     {
 155       ggc_mark_tree (a->id);
 156       a = a->prev;
 157     }
 158 }
 159 #else  /* not HANDLE_PRAGMA_PACK_PUSH_POP */
 160 #define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
 161 #define push_alignment(ID, N) \
 162     BAD("#pragma pack(push[, id], <n>) is not supported on this target")
 163 #define pop_alignment(ID) \
 164     BAD("#pragma pack(pop[, id], <n>) is not supported on this target")
 165 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 166
 167 /* #pragma pack ()
 168    #pragma pack (N)
 169
 170    #pragma pack (push, N)
 171    #pragma pack (push, ID, N)
 172    #pragma pack (pop)
 173    #pragma pack (pop, ID) */
 174 static void
 175 handle_pragma_pack (dummy)
 176      cpp_reader *dummy ATTRIBUTE_UNUSED;
 177 {
 178   tree x, id = 0;
 179   int align = -1;
 180   enum cpp_ttype token;
 181   enum { set, push, pop } action;
 182
 183   if (c_lex (&x) != CPP_OPEN_PAREN)
 184     BAD ("missing '(' after '#pragma pack' - ignored");
 185
 186   token = c_lex (&x);
 187   if (token == CPP_CLOSE_PAREN)
 188     {
 189       action = set;
 190       align = 0;
 191     }
 192   else if (token == CPP_NUMBER)
 193     {
 194       align = TREE_INT_CST_LOW (x);
 195       action = set;
 196       if (c_lex (&x) != CPP_CLOSE_PAREN)
 197         BAD ("malformed '#pragma pack' - ignored");
 198     }
 199   else if (token == CPP_NAME)
 200     {
 201 #define BAD_ACTION do { if (action == push) \
 202           BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
 203         else \
 204           BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
 205         } while (0)
 206
 207       const char *op = IDENTIFIER_POINTER (x);
 208       if (!strcmp (op, "push"))
 209         action = push;
 210       else if (!strcmp (op, "pop"))
 211         action = pop;
 212       else
 213         BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
 214
 215       token = c_lex (&x);
 216       if (token != CPP_COMMA && action == push)
 217         BAD_ACTION;
 218
 219       if (token == CPP_COMMA)
 220         {
 221           token = c_lex (&x);
 222           if (token == CPP_NAME)
 223             {
 224               id = x;
 225               if (action == push && c_lex (&x) != CPP_COMMA)
 226                 BAD_ACTION;
 227               token = c_lex (&x);
 228             }
 229
 230           if (action == push)
 231             {
 232               if (token == CPP_NUMBER)
 233                 {
 234                   align = TREE_INT_CST_LOW (x);
 235                   token = c_lex (&x);
 236                 }
 237               else
 238                 BAD_ACTION;
 239             }
 240         }
 241
 242       if (token != CPP_CLOSE_PAREN)
 243         BAD_ACTION;
 244 #undef BAD_ACTION
 245     }
 246   else
 247     BAD ("malformed '#pragma pack' - ignored");
 248
 249   if (c_lex (&x) != CPP_EOF)
 250     warning ("junk at end of '#pragma pack'");
 251
 252   if (action != pop)
 253     switch (align)
 254       {
 255       case 0:
 256       case 1:
 257       case 2:
 258       case 4:
 259       case 8:
 260       case 16:
 261         align *= BITS_PER_UNIT;
 262         break;
 263       default:
 264         BAD2 ("alignment must be a small power of two, not %d", align);
 265       }
 266
 267   switch (action)
 268     {
 269     case set:   SET_GLOBAL_ALIGNMENT (align);  break;
 270     case push:  push_alignment (align, id);    break;
 271     case pop:   pop_alignment (id);            break;
 272     }
 273 }
 274 #endif  /* HANDLE_PRAGMA_PACK */
 275
 276 #ifdef HANDLE_PRAGMA_WEAK
 277 static void handle_pragma_weak PARAMS ((cpp_reader *));
 278
 279 /* #pragma weak name [= value] */
 280 static void
 281 handle_pragma_weak (dummy)
 282      cpp_reader *dummy ATTRIBUTE_UNUSED;
 283 {
 284   tree name, value, x;
 285   enum cpp_ttype t;
 286
 287   value = 0;
 288
 289   if (c_lex (&name) != CPP_NAME)
 290     BAD ("malformed #pragma weak, ignored");
 291   t = c_lex (&x);
 292   if (t == CPP_EQ)
 293     {
 294       if (c_lex (&value) != CPP_NAME)
 295         BAD ("malformed #pragma weak, ignored");
 296       t = c_lex (&x);
 297     }
 298   if (t != CPP_EOF)
 299     warning ("junk at end of #pragma weak");
 300
 301   add_weak (IDENTIFIER_POINTER (name), value ? IDENTIFIER_POINTER (value) : 0);
 302 }
 303 #endif
 304
 305 void
 306 init_pragma ()
 307 {
 308 #ifdef HANDLE_PRAGMA_PACK
 309   cpp_register_pragma (parse_in, 0, "pack", handle_pragma_pack);
 310 #endif
 311 #ifdef HANDLE_PRAGMA_WEAK
 312   cpp_register_pragma (parse_in, 0, "weak", handle_pragma_weak);
 313 #endif
 314 #ifdef REGISTER_TARGET_PRAGMAS
 315   REGISTER_TARGET_PRAGMAS (parse_in);
 316 #endif
 317
 318 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
 319   ggc_add_root (&alignment_stack, 1, sizeof(alignment_stack),
 320                 mark_align_stack);
 321 #endif
 322 }