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, 2002
   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-common.h"
  33 #include "output.h"
  34 #include "tm_p.h"
  35
  36 #define GCC_BAD(msgid) do { warning (msgid); return; } while (0)
  37 #define GCC_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   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     GCC_BAD("#pragma pack(push[, id], <n>) is not supported on this target")
 162 #define pop_alignment(ID) \
 163     GCC_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     GCC_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         GCC_BAD ("malformed '#pragma pack' - ignored");
 197     }
 198   else if (token == CPP_NAME)
 199     {
 200 #define GCC_BAD_ACTION do { if (action == push) \
 201           GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
 202         else \
 203           GCC_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         GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
 213
 214       token = c_lex (&x);
 215       if (token != CPP_COMMA && action == push)
 216         GCC_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                 GCC_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                 GCC_BAD_ACTION;
 238             }
 239         }
 240
 241       if (token != CPP_CLOSE_PAREN)
 242         GCC_BAD_ACTION;
 243 #undef GCC_BAD_ACTION
 244     }
 245   else
 246     GCC_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         GCC_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 apply_pragma_weak PARAMS ((tree, tree));
 277 static void handle_pragma_weak PARAMS ((cpp_reader *));
 278
 279 static tree pending_weaks;
 280
 281 static void
 282 apply_pragma_weak (decl, value)
 283      tree decl, value;
 284 {
 285   if (value)
 286     {
 287       value = build_string (IDENTIFIER_LENGTH (value),
 288                             IDENTIFIER_POINTER (value));
 289       decl_attributes (&decl, build_tree_list (get_identifier ("alias"),
 290                                                build_tree_list (NULL, value)),
 291                        0);
 292     }
 293
 294   if (SUPPORTS_WEAK && DECL_EXTERNAL (decl) && TREE_USED (decl)
 295       && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
 296     warning_with_decl (decl, "applying #pragma weak `%s' after first use results in unspecified behavior");
 297
 298   declare_weak (decl);
 299 }
 300
 301 void
 302 maybe_apply_pragma_weak (decl)
 303      tree decl;
 304 {
 305   tree *p, t, id;
 306
 307   /* Copied from the check in set_decl_assembler_name.  */
 308   if (TREE_CODE (decl) == FUNCTION_DECL
 309       || (TREE_CODE (decl) == VAR_DECL
 310           && (TREE_STATIC (decl)
 311               || DECL_EXTERNAL (decl)
 312               || TREE_PUBLIC (decl))))
 313     id = DECL_ASSEMBLER_NAME (decl);
 314   else
 315     return;
 316
 317   for (p = &pending_weaks; (t = *p) ; p = &TREE_CHAIN (t))
 318     if (id == TREE_PURPOSE (t))
 319       {
 320         apply_pragma_weak (decl, TREE_VALUE (t));
 321         *p = TREE_CHAIN (t);
 322         break;
 323       }
 324 }
 325
 326 /* #pragma weak name [= value] */
 327 static void
 328 handle_pragma_weak (dummy)
 329      cpp_reader *dummy ATTRIBUTE_UNUSED;
 330 {
 331   tree name, value, x, decl;
 332   enum cpp_ttype t;
 333
 334   value = 0;
 335
 336   if (c_lex (&name) != CPP_NAME)
 337     GCC_BAD ("malformed #pragma weak, ignored");
 338   t = c_lex (&x);
 339   if (t == CPP_EQ)
 340     {
 341       if (c_lex (&value) != CPP_NAME)
 342         GCC_BAD ("malformed #pragma weak, ignored");
 343       t = c_lex (&x);
 344     }
 345   if (t != CPP_EOF)
 346     warning ("junk at end of #pragma weak");
 347
 348   decl = identifier_global_value (name);
 349   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 350     {
 351       apply_pragma_weak (decl, value);
 352       if (value)
 353         assemble_alias (decl, value);
 354     }
 355   else
 356     pending_weaks = tree_cons (name, value, pending_weaks);
 357 }
 358 #else
 359 void
 360 maybe_apply_pragma_weak (decl)
 361      tree decl ATTRIBUTE_UNUSED;
 362 {
 363 }
 364 #endif /* HANDLE_PRAGMA_WEAK */
 365
 366 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 367 static void handle_pragma_redefine_extname PARAMS ((cpp_reader *));
 368
 369 static tree pending_redefine_extname;
 370
 371 /* #pragma redefined_extname oldname newname */
 372 static void
 373 handle_pragma_redefine_extname (dummy)
 374      cpp_reader *dummy ATTRIBUTE_UNUSED;
 375 {
 376   tree oldname, newname, decl, x;
 377   enum cpp_ttype t;
 378
 379   if (c_lex (&oldname) != CPP_NAME)
 380     {
 381       warning ("malformed #pragma redefine_extname, ignored");
 382       return;
 383     }
 384   if (c_lex (&newname) != CPP_NAME)
 385     {
 386       warning ("malformed #pragma redefine_extname, ignored");
 387       return;
 388     }
 389   t = c_lex (&x);
 390   if (t != CPP_EOF)
 391     warning ("junk at end of #pragma redefine_extname");
 392
 393   decl = identifier_global_value (oldname);
 394   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 395     {
 396       if (DECL_ASSEMBLER_NAME_SET_P (decl)
 397           && DECL_ASSEMBLER_NAME (decl) != newname)
 398         warning ("#pragma redefine_extname conflicts with declaration");
 399       SET_DECL_ASSEMBLER_NAME (decl, newname);
 400     }
 401   else
 402     pending_redefine_extname
 403       = tree_cons (oldname, newname, pending_redefine_extname);
 404 }
 405 #endif
 406
 407 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 408 static void handle_pragma_extern_prefix PARAMS ((cpp_reader *));
 409
 410 static tree pragma_extern_prefix;
 411
 412 /* #pragma extern_prefix "prefix" */
 413 static void
 414 handle_pragma_extern_prefix (dummy)
 415      cpp_reader *dummy ATTRIBUTE_UNUSED;
 416 {
 417   tree prefix, x;
 418   enum cpp_ttype t;
 419
 420   if (c_lex (&prefix) != CPP_STRING)
 421     {
 422       warning ("malformed #pragma extern_prefix, ignored");
 423       return;
 424     }
 425   t = c_lex (&x);
 426   if (t != CPP_EOF)
 427     warning ("junk at end of #pragma extern_prefix");
 428
 429   /* Note that the length includes the null terminator.  */
 430   pragma_extern_prefix = (TREE_STRING_LENGTH (prefix) > 1 ? prefix : NULL);
 431 }
 432 #endif
 433
 434 /* Hook from the front ends to apply the results of one of the preceeding
 435    pragmas that rename variables.  */
 436
 437 tree
 438 maybe_apply_renaming_pragma (decl, asmname)
 439      tree decl, asmname;
 440 {
 441   tree oldname;
 442
 443   /* Copied from the check in set_decl_assembler_name.  */
 444   if (TREE_CODE (decl) == FUNCTION_DECL
 445       || (TREE_CODE (decl) == VAR_DECL
 446           && (TREE_STATIC (decl)
 447               || DECL_EXTERNAL (decl)
 448               || TREE_PUBLIC (decl))))
 449     oldname = DECL_ASSEMBLER_NAME (decl);
 450   else
 451     return asmname;
 452
 453   /* If the name begins with a *, that's a sign of an asmname attached to
 454      a previous declaration.  */
 455   if (IDENTIFIER_POINTER (oldname)[0] == '*')
 456     {
 457       const char *oldasmname = IDENTIFIER_POINTER (oldname) + 1;
 458       if (asmname && strcmp (TREE_STRING_POINTER (asmname), oldasmname) != 0)
 459         warning ("asm declaration conficts with previous rename");
 460       asmname = build_string (strlen (oldasmname), oldasmname);
 461     }
 462
 463 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 464   {
 465     tree *p, t;
 466
 467     for (p = &pending_redefine_extname; (t = *p) ; p = &TREE_CHAIN (t))
 468       if (oldname == TREE_PURPOSE (t))
 469         {
 470           const char *newname = IDENTIFIER_POINTER (TREE_VALUE (t));
 471
 472           if (asmname && strcmp (TREE_STRING_POINTER (asmname), newname) != 0)
 473             warning ("#pragma redefine_extname conflicts with declaration");
 474           *p = TREE_CHAIN (t);
 475
 476           return build_string (strlen (newname), newname);
 477         }
 478   }
 479 #endif
 480
 481 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 482   if (pragma_extern_prefix && !asmname)
 483     {
 484       char *x = concat (TREE_STRING_POINTER (pragma_extern_prefix),
 485                         IDENTIFIER_POINTER (oldname), NULL);
 486       asmname = build_string (strlen (x), x);
 487       free (x);
 488       return asmname;
 489     }
 490 #endif
 491
 492   return asmname;
 493 }
 494
 495 void
 496 init_pragma ()
 497 {
 498 #ifdef HANDLE_PRAGMA_PACK
 499   cpp_register_pragma (parse_in, 0, "pack", handle_pragma_pack);
 500 #endif
 501 #ifdef HANDLE_PRAGMA_WEAK
 502   cpp_register_pragma (parse_in, 0, "weak", handle_pragma_weak);
 503   ggc_add_tree_root (&pending_weaks, 1);
 504 #endif
 505 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 506   cpp_register_pragma (parse_in, 0, "redefine_extname",
 507                        handle_pragma_redefine_extname);
 508   ggc_add_tree_root (&pending_redefine_extname, 1);
 509 #endif
 510 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 511   cpp_register_pragma (parse_in, 0, "extern_prefix",
 512                        handle_pragma_extern_prefix);
 513   ggc_add_tree_root (&pragma_extern_prefix, 1);
 514 #endif
 515
 516 #ifdef REGISTER_TARGET_PRAGMAS
 517   REGISTER_TARGET_PRAGMAS (parse_in);
 518 #endif
 519
 520 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
 521   ggc_add_root (&alignment_stack, 1, sizeof(alignment_stack),
 522                 mark_align_stack);
 523 #endif
 524 }