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