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, 2003
   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 "coretypes.h"
  25 #include "tm.h"
  26 #include "rtl.h"
  27 #include "tree.h"
  28 #include "function.h"
  29 #include "cpplib.h"
  30 #include "c-pragma.h"
  31 #include "flags.h"
  32 #include "toplev.h"
  33 #include "ggc.h"
  34 #include "c-common.h"
  35 #include "output.h"
  36 #include "tm_p.h"
  37
  38 #define GCC_BAD(msgid) do { warning (msgid); return; } while (0)
  39 #define GCC_BAD2(msgid, arg) do { warning (msgid, arg); return; } while (0)
  40
  41 typedef struct align_stack GTY(())
  42 {
  43   int                  alignment;
  44   unsigned int         num_pushes;
  45   tree                 id;
  46   struct align_stack * prev;
  47 } align_stack;
  48
  49 static GTY(()) struct align_stack * alignment_stack;
  50
  51 #ifdef HANDLE_PRAGMA_PACK
  52 static void handle_pragma_pack (cpp_reader *);
  53
  54 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
  55 /* If we have a "global" #pragma pack(<n>) in effect when the first
  56    #pragma pack(push,<n>) is encountered, this stores the value of
  57    maximum_field_alignment in effect.  When the final pop_alignment()
  58    happens, we restore the value to this, not to a value of 0 for
  59    maximum_field_alignment.  Value is in bits.  */
  60 static int default_alignment;
  61 #define SET_GLOBAL_ALIGNMENT(ALIGN) \
  62   (default_alignment = maximum_field_alignment = (ALIGN))
  63
  64 static void push_alignment (int, tree);
  65 static void pop_alignment (tree);
  66
  67 /* Push an alignment value onto the stack.  */
  68 static void
  69 push_alignment (int alignment, tree id)
  70 {
  71   if (alignment_stack == NULL
  72       || alignment_stack->alignment != alignment
  73       || id != NULL_TREE)
  74     {
  75       align_stack * entry;
  76
  77       entry = (align_stack *) ggc_alloc (sizeof (* entry));
  78
  79       entry->alignment  = alignment;
  80       entry->num_pushes = 1;
  81       entry->id         = id;
  82       entry->prev       = alignment_stack;
  83
  84       /* The current value of maximum_field_alignment is not necessarily
  85          0 since there may be a #pragma pack(<n>) in effect; remember it
  86          so that we can restore it after the final #pragma pop().  */
  87       if (alignment_stack == NULL)
  88         default_alignment = maximum_field_alignment;
  89
  90       alignment_stack = entry;
  91
  92       maximum_field_alignment = alignment;
  93     }
  94   else
  95     alignment_stack->num_pushes ++;
  96 }
  97
  98 /* Undo a push of an alignment onto the stack.  */
  99 static void
 100 pop_alignment (tree id)
 101 {
 102   align_stack * entry;
 103
 104   if (alignment_stack == NULL)
 105     {
 106       warning ("\
 107 #pragma pack (pop) encountered without matching #pragma pack (push, <n>)"
 108                );
 109       return;
 110     }
 111
 112   /* If we got an identifier, strip away everything above the target
 113      entry so that the next step will restore the state just below it.  */
 114   if (id)
 115     {
 116       for (entry = alignment_stack; entry; entry = entry->prev)
 117         if (entry->id == id)
 118           {
 119             entry->num_pushes = 1;
 120             alignment_stack = entry;
 121             break;
 122           }
 123       if (entry == NULL)
 124         warning ("\
 125 #pragma pack(pop, %s) encountered without matching #pragma pack(push, %s, <n>)"
 126                  , IDENTIFIER_POINTER (id), IDENTIFIER_POINTER (id));
 127     }
 128
 129   if (-- alignment_stack->num_pushes == 0)
 130     {
 131       entry = alignment_stack->prev;
 132
 133       if (entry == NULL)
 134         maximum_field_alignment = default_alignment;
 135       else
 136         maximum_field_alignment = entry->alignment;
 137
 138       alignment_stack = entry;
 139     }
 140 }
 141 #else  /* not HANDLE_PRAGMA_PACK_PUSH_POP */
 142 #define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
 143 #define push_alignment(ID, N) \
 144     GCC_BAD("#pragma pack(push[, id], <n>) is not supported on this target")
 145 #define pop_alignment(ID) \
 146     GCC_BAD("#pragma pack(pop[, id], <n>) is not supported on this target")
 147 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 148
 149 /* #pragma pack ()
 150    #pragma pack (N)
 151
 152    #pragma pack (push, N)
 153    #pragma pack (push, ID, N)
 154    #pragma pack (pop)
 155    #pragma pack (pop, ID) */
 156 static void
 157 handle_pragma_pack (cpp_reader *dummy ATTRIBUTE_UNUSED)
 158 {
 159   tree x, id = 0;
 160   int align = -1;
 161   enum cpp_ttype token;
 162   enum { set, push, pop } action;
 163
 164   if (c_lex (&x) != CPP_OPEN_PAREN)
 165     GCC_BAD ("missing '(' after '#pragma pack' - ignored");
 166
 167   token = c_lex (&x);
 168   if (token == CPP_CLOSE_PAREN)
 169     {
 170       action = set;
 171       align = 0;
 172     }
 173   else if (token == CPP_NUMBER)
 174     {
 175       align = TREE_INT_CST_LOW (x);
 176       action = set;
 177       if (c_lex (&x) != CPP_CLOSE_PAREN)
 178         GCC_BAD ("malformed '#pragma pack' - ignored");
 179     }
 180   else if (token == CPP_NAME)
 181     {
 182 #define GCC_BAD_ACTION do { if (action == push) \
 183           GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
 184         else \
 185           GCC_BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
 186         } while (0)
 187
 188       const char *op = IDENTIFIER_POINTER (x);
 189       if (!strcmp (op, "push"))
 190         action = push;
 191       else if (!strcmp (op, "pop"))
 192         action = pop;
 193       else
 194         GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
 195
 196       token = c_lex (&x);
 197       if (token != CPP_COMMA && action == push)
 198         GCC_BAD_ACTION;
 199
 200       if (token == CPP_COMMA)
 201         {
 202           token = c_lex (&x);
 203           if (token == CPP_NAME)
 204             {
 205               id = x;
 206               if (action == push && c_lex (&x) != CPP_COMMA)
 207                 GCC_BAD_ACTION;
 208               token = c_lex (&x);
 209             }
 210
 211           if (action == push)
 212             {
 213               if (token == CPP_NUMBER)
 214                 {
 215                   align = TREE_INT_CST_LOW (x);
 216                   token = c_lex (&x);
 217                 }
 218               else
 219                 GCC_BAD_ACTION;
 220             }
 221         }
 222
 223       if (token != CPP_CLOSE_PAREN)
 224         GCC_BAD_ACTION;
 225 #undef GCC_BAD_ACTION
 226     }
 227   else
 228     GCC_BAD ("malformed '#pragma pack' - ignored");
 229
 230   if (c_lex (&x) != CPP_EOF)
 231     warning ("junk at end of '#pragma pack'");
 232
 233   if (action != pop)
 234     switch (align)
 235       {
 236       case 0:
 237       case 1:
 238       case 2:
 239       case 4:
 240       case 8:
 241       case 16:
 242         align *= BITS_PER_UNIT;
 243         break;
 244       default:
 245         GCC_BAD2 ("alignment must be a small power of two, not %d", align);
 246       }
 247
 248   switch (action)
 249     {
 250     case set:   SET_GLOBAL_ALIGNMENT (align);  break;
 251     case push:  push_alignment (align, id);    break;
 252     case pop:   pop_alignment (id);            break;
 253     }
 254 }
 255 #endif  /* HANDLE_PRAGMA_PACK */
 256
 257 static GTY(()) tree pending_weaks;
 258
 259 #ifdef HANDLE_PRAGMA_WEAK
 260 static void apply_pragma_weak (tree, tree);
 261 static void handle_pragma_weak (cpp_reader *);
 262
 263 static void
 264 apply_pragma_weak (tree decl, tree value)
 265 {
 266   if (value)
 267     {
 268       value = build_string (IDENTIFIER_LENGTH (value),
 269                             IDENTIFIER_POINTER (value));
 270       decl_attributes (&decl, build_tree_list (get_identifier ("alias"),
 271                                                build_tree_list (NULL, value)),
 272                        0);
 273     }
 274
 275   if (SUPPORTS_WEAK && DECL_EXTERNAL (decl) && TREE_USED (decl)
 276       && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
 277     warning_with_decl (decl, "applying #pragma weak `%s' after first use results in unspecified behavior");
 278
 279   declare_weak (decl);
 280 }
 281
 282 void
 283 maybe_apply_pragma_weak (tree decl)
 284 {
 285   tree *p, t, id;
 286
 287   /* Copied from the check in set_decl_assembler_name.  */
 288   if (TREE_CODE (decl) == FUNCTION_DECL
 289       || (TREE_CODE (decl) == VAR_DECL
 290           && (TREE_STATIC (decl)
 291               || DECL_EXTERNAL (decl)
 292               || TREE_PUBLIC (decl))))
 293     id = DECL_ASSEMBLER_NAME (decl);
 294   else
 295     return;
 296
 297   for (p = &pending_weaks; (t = *p) ; p = &TREE_CHAIN (t))
 298     if (id == TREE_PURPOSE (t))
 299       {
 300         apply_pragma_weak (decl, TREE_VALUE (t));
 301         *p = TREE_CHAIN (t);
 302         break;
 303       }
 304 }
 305
 306 /* #pragma weak name [= value] */
 307 static void
 308 handle_pragma_weak (cpp_reader *dummy ATTRIBUTE_UNUSED)
 309 {
 310   tree name, value, x, decl;
 311   enum cpp_ttype t;
 312
 313   value = 0;
 314
 315   if (c_lex (&name) != CPP_NAME)
 316     GCC_BAD ("malformed #pragma weak, ignored");
 317   t = c_lex (&x);
 318   if (t == CPP_EQ)
 319     {
 320       if (c_lex (&value) != CPP_NAME)
 321         GCC_BAD ("malformed #pragma weak, ignored");
 322       t = c_lex (&x);
 323     }
 324   if (t != CPP_EOF)
 325     warning ("junk at end of #pragma weak");
 326
 327   decl = identifier_global_value (name);
 328   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 329     {
 330       apply_pragma_weak (decl, value);
 331       if (value)
 332         assemble_alias (decl, value);
 333     }
 334   else
 335     pending_weaks = tree_cons (name, value, pending_weaks);
 336 }
 337 #else
 338 void
 339 maybe_apply_pragma_weak (tree decl ATTRIBUTE_UNUSED)
 340 {
 341 }
 342 #endif /* HANDLE_PRAGMA_WEAK */
 343
 344 static GTY(()) tree pending_redefine_extname;
 345
 346 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 347 static void handle_pragma_redefine_extname (cpp_reader *);
 348
 349 /* #pragma redefined_extname oldname newname */
 350 static void
 351 handle_pragma_redefine_extname (cpp_reader *dummy ATTRIBUTE_UNUSED)
 352 {
 353   tree oldname, newname, decl, x;
 354   enum cpp_ttype t;
 355
 356   if (c_lex (&oldname) != CPP_NAME)
 357     {
 358       warning ("malformed #pragma redefine_extname, ignored");
 359       return;
 360     }
 361   if (c_lex (&newname) != CPP_NAME)
 362     {
 363       warning ("malformed #pragma redefine_extname, ignored");
 364       return;
 365     }
 366   t = c_lex (&x);
 367   if (t != CPP_EOF)
 368     warning ("junk at end of #pragma redefine_extname");
 369
 370   decl = identifier_global_value (oldname);
 371   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 372     {
 373       if (DECL_ASSEMBLER_NAME_SET_P (decl)
 374           && DECL_ASSEMBLER_NAME (decl) != newname)
 375         warning ("#pragma redefine_extname conflicts with declaration");
 376       SET_DECL_ASSEMBLER_NAME (decl, newname);
 377     }
 378   else
 379     add_to_renaming_pragma_list(oldname, newname);
 380 }
 381 #endif
 382
 383 void
 384 add_to_renaming_pragma_list (tree oldname, tree newname)
 385 {
 386   pending_redefine_extname
 387     = tree_cons (oldname, newname, pending_redefine_extname);
 388 }
 389
 390 static GTY(()) tree pragma_extern_prefix;
 391
 392 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 393 static void handle_pragma_extern_prefix (cpp_reader *);
 394
 395 /* #pragma extern_prefix "prefix" */
 396 static void
 397 handle_pragma_extern_prefix (cpp_reader *dummy ATTRIBUTE_UNUSED)
 398 {
 399   tree prefix, x;
 400   enum cpp_ttype t;
 401
 402   if (c_lex (&prefix) != CPP_STRING)
 403     {
 404       warning ("malformed #pragma extern_prefix, ignored");
 405       return;
 406     }
 407   t = c_lex (&x);
 408   if (t != CPP_EOF)
 409     warning ("junk at end of #pragma extern_prefix");
 410
 411   /* Note that the length includes the null terminator.  */
 412   pragma_extern_prefix = (TREE_STRING_LENGTH (prefix) > 1 ? prefix : NULL);
 413 }
 414 #endif
 415
 416 /* Hook from the front ends to apply the results of one of the preceding
 417    pragmas that rename variables.  */
 418
 419 tree
 420 maybe_apply_renaming_pragma (tree decl, tree asmname)
 421 {
 422   tree oldname;
 423
 424   /* Copied from the check in set_decl_assembler_name.  */
 425   if (TREE_CODE (decl) == FUNCTION_DECL
 426       || (TREE_CODE (decl) == VAR_DECL
 427           && (TREE_STATIC (decl)
 428               || DECL_EXTERNAL (decl)
 429               || TREE_PUBLIC (decl))))
 430     oldname = DECL_ASSEMBLER_NAME (decl);
 431   else
 432     return asmname;
 433
 434   /* If the name begins with a *, that's a sign of an asmname attached to
 435      a previous declaration.  */
 436   if (IDENTIFIER_POINTER (oldname)[0] == '*')
 437     {
 438       const char *oldasmname = IDENTIFIER_POINTER (oldname) + 1;
 439       if (asmname && strcmp (TREE_STRING_POINTER (asmname), oldasmname) != 0)
 440         warning ("asm declaration conflicts with previous rename");
 441       asmname = build_string (strlen (oldasmname), oldasmname);
 442     }
 443
 444   {
 445     tree *p, t;
 446
 447     for (p = &pending_redefine_extname; (t = *p) ; p = &TREE_CHAIN (t))
 448       if (oldname == TREE_PURPOSE (t))
 449         {
 450           const char *newname = IDENTIFIER_POINTER (TREE_VALUE (t));
 451
 452           if (asmname && strcmp (TREE_STRING_POINTER (asmname), newname) != 0)
 453             warning ("#pragma redefine_extname conflicts with declaration");
 454           *p = TREE_CHAIN (t);
 455
 456           return build_string (strlen (newname), newname);
 457         }
 458   }
 459
 460 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 461   if (pragma_extern_prefix && !asmname)
 462     {
 463       char *x = concat (TREE_STRING_POINTER (pragma_extern_prefix),
 464                         IDENTIFIER_POINTER (oldname), NULL);
 465       asmname = build_string (strlen (x), x);
 466       free (x);
 467       return asmname;
 468     }
 469 #endif
 470
 471   return asmname;
 472 }
 473
 474 /* Front-end wrapper for pragma registration to avoid dragging
 475    cpplib.h in almost everywhere.  */
 476 void
 477 c_register_pragma (const char *space, const char *name,
 478                    void (*handler) (struct cpp_reader *))
 479 {
 480   cpp_register_pragma (parse_in, space, name, handler);
 481 }
 482
 483 /* Set up front-end pragmas.  */
 484 void
 485 init_pragma (void)
 486 {
 487 #ifdef HANDLE_PRAGMA_PACK
 488   c_register_pragma (0, "pack", handle_pragma_pack);
 489 #endif
 490 #ifdef HANDLE_PRAGMA_WEAK
 491   c_register_pragma (0, "weak", handle_pragma_weak);
 492 #endif
 493 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 494   c_register_pragma (0, "redefine_extname", handle_pragma_redefine_extname);
 495 #endif
 496 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 497   c_register_pragma (0, "extern_prefix", handle_pragma_extern_prefix);
 498 #endif
 499
 500 #ifdef REGISTER_TARGET_PRAGMAS
 501   REGISTER_TARGET_PRAGMAS ();
 502 #endif
 503 }
 504
 505 #include "gt-c-pragma.h"