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 typedef struct align_stack GTY(())
  40 {
  41   int                  alignment;
  42   unsigned int         num_pushes;
  43   tree                 id;
  44   struct align_stack * prev;
  45 } align_stack;
  46
  47 static GTY(()) struct align_stack * alignment_stack;
  48
  49 #ifdef HANDLE_PRAGMA_PACK
  50 static void handle_pragma_pack PARAMS ((cpp_reader *));
  51
  52 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
  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
  65 /* Push an alignment value onto the stack.  */
  66 static void
  67 push_alignment (alignment, id)
  68      int alignment;
  69      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 (id)
 101      tree id;
 102 {
 103   align_stack * entry;
 104
 105   if (alignment_stack == NULL)
 106     {
 107       warning ("\
 108 #pragma pack (pop) encountered without matching #pragma pack (push, <n>)"
 109                );
 110       return;
 111     }
 112
 113   /* If we got an identifier, strip away everything above the target
 114      entry so that the next step will restore the state just below it.  */
 115   if (id)
 116     {
 117       for (entry = alignment_stack; entry; entry = entry->prev)
 118         if (entry->id == id)
 119           {
 120             entry->num_pushes = 1;
 121             alignment_stack = entry;
 122             break;
 123           }
 124       if (entry == NULL)
 125         warning ("\
 126 #pragma pack(pop, %s) encountered without matching #pragma pack(push, %s, <n>)"
 127                  , IDENTIFIER_POINTER (id), IDENTIFIER_POINTER (id));
 128     }
 129
 130   if (-- alignment_stack->num_pushes == 0)
 131     {
 132       entry = alignment_stack->prev;
 133
 134       if (entry == NULL)
 135         maximum_field_alignment = default_alignment;
 136       else
 137         maximum_field_alignment = entry->alignment;
 138
 139       alignment_stack = entry;
 140     }
 141 }
 142 #else  /* not HANDLE_PRAGMA_PACK_PUSH_POP */
 143 #define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
 144 #define push_alignment(ID, N) \
 145     GCC_BAD("#pragma pack(push[, id], <n>) is not supported on this target")
 146 #define pop_alignment(ID) \
 147     GCC_BAD("#pragma pack(pop[, id], <n>) is not supported on this target")
 148 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 149
 150 /* #pragma pack ()
 151    #pragma pack (N)
 152
 153    #pragma pack (push, N)
 154    #pragma pack (push, ID, N)
 155    #pragma pack (pop)
 156    #pragma pack (pop, ID) */
 157 static void
 158 handle_pragma_pack (dummy)
 159      cpp_reader *dummy ATTRIBUTE_UNUSED;
 160 {
 161   tree x, id = 0;
 162   int align = -1;
 163   enum cpp_ttype token;
 164   enum { set, push, pop } action;
 165
 166   if (c_lex (&x) != CPP_OPEN_PAREN)
 167     GCC_BAD ("missing '(' after '#pragma pack' - ignored");
 168
 169   token = c_lex (&x);
 170   if (token == CPP_CLOSE_PAREN)
 171     {
 172       action = set;
 173       align = 0;
 174     }
 175   else if (token == CPP_NUMBER)
 176     {
 177       align = TREE_INT_CST_LOW (x);
 178       action = set;
 179       if (c_lex (&x) != CPP_CLOSE_PAREN)
 180         GCC_BAD ("malformed '#pragma pack' - ignored");
 181     }
 182   else if (token == CPP_NAME)
 183     {
 184 #define GCC_BAD_ACTION do { if (action == push) \
 185           GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
 186         else \
 187           GCC_BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
 188         } while (0)
 189
 190       const char *op = IDENTIFIER_POINTER (x);
 191       if (!strcmp (op, "push"))
 192         action = push;
 193       else if (!strcmp (op, "pop"))
 194         action = pop;
 195       else
 196         GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
 197
 198       token = c_lex (&x);
 199       if (token != CPP_COMMA && action == push)
 200         GCC_BAD_ACTION;
 201
 202       if (token == CPP_COMMA)
 203         {
 204           token = c_lex (&x);
 205           if (token == CPP_NAME)
 206             {
 207               id = x;
 208               if (action == push && c_lex (&x) != CPP_COMMA)
 209                 GCC_BAD_ACTION;
 210               token = c_lex (&x);
 211             }
 212
 213           if (action == push)
 214             {
 215               if (token == CPP_NUMBER)
 216                 {
 217                   align = TREE_INT_CST_LOW (x);
 218                   token = c_lex (&x);
 219                 }
 220               else
 221                 GCC_BAD_ACTION;
 222             }
 223         }
 224
 225       if (token != CPP_CLOSE_PAREN)
 226         GCC_BAD_ACTION;
 227 #undef GCC_BAD_ACTION
 228     }
 229   else
 230     GCC_BAD ("malformed '#pragma pack' - ignored");
 231
 232   if (c_lex (&x) != CPP_EOF)
 233     warning ("junk at end of '#pragma pack'");
 234
 235   if (action != pop)
 236     switch (align)
 237       {
 238       case 0:
 239       case 1:
 240       case 2:
 241       case 4:
 242       case 8:
 243       case 16:
 244         align *= BITS_PER_UNIT;
 245         break;
 246       default:
 247         GCC_BAD2 ("alignment must be a small power of two, not %d", align);
 248       }
 249
 250   switch (action)
 251     {
 252     case set:   SET_GLOBAL_ALIGNMENT (align);  break;
 253     case push:  push_alignment (align, id);    break;
 254     case pop:   pop_alignment (id);            break;
 255     }
 256 }
 257 #endif  /* HANDLE_PRAGMA_PACK */
 258
 259 static GTY(()) tree pending_weaks;
 260
 261 #ifdef HANDLE_PRAGMA_WEAK
 262 static void apply_pragma_weak PARAMS ((tree, tree));
 263 static void handle_pragma_weak PARAMS ((cpp_reader *));
 264
 265 static void
 266 apply_pragma_weak (decl, value)
 267      tree decl, value;
 268 {
 269   if (value)
 270     {
 271       value = build_string (IDENTIFIER_LENGTH (value),
 272                             IDENTIFIER_POINTER (value));
 273       decl_attributes (&decl, build_tree_list (get_identifier ("alias"),
 274                                                build_tree_list (NULL, value)),
 275                        0);
 276     }
 277
 278   if (SUPPORTS_WEAK && DECL_EXTERNAL (decl) && TREE_USED (decl)
 279       && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
 280     warning_with_decl (decl, "applying #pragma weak `%s' after first use results in unspecified behavior");
 281
 282   declare_weak (decl);
 283 }
 284
 285 void
 286 maybe_apply_pragma_weak (decl)
 287      tree decl;
 288 {
 289   tree *p, t, id;
 290
 291   /* Copied from the check in set_decl_assembler_name.  */
 292   if (TREE_CODE (decl) == FUNCTION_DECL
 293       || (TREE_CODE (decl) == VAR_DECL
 294           && (TREE_STATIC (decl)
 295               || DECL_EXTERNAL (decl)
 296               || TREE_PUBLIC (decl))))
 297     id = DECL_ASSEMBLER_NAME (decl);
 298   else
 299     return;
 300
 301   for (p = &pending_weaks; (t = *p) ; p = &TREE_CHAIN (t))
 302     if (id == TREE_PURPOSE (t))
 303       {
 304         apply_pragma_weak (decl, TREE_VALUE (t));
 305         *p = TREE_CHAIN (t);
 306         break;
 307       }
 308 }
 309
 310 /* #pragma weak name [= value] */
 311 static void
 312 handle_pragma_weak (dummy)
 313      cpp_reader *dummy ATTRIBUTE_UNUSED;
 314 {
 315   tree name, value, x, decl;
 316   enum cpp_ttype t;
 317
 318   value = 0;
 319
 320   if (c_lex (&name) != CPP_NAME)
 321     GCC_BAD ("malformed #pragma weak, ignored");
 322   t = c_lex (&x);
 323   if (t == CPP_EQ)
 324     {
 325       if (c_lex (&value) != CPP_NAME)
 326         GCC_BAD ("malformed #pragma weak, ignored");
 327       t = c_lex (&x);
 328     }
 329   if (t != CPP_EOF)
 330     warning ("junk at end of #pragma weak");
 331
 332   decl = identifier_global_value (name);
 333   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 334     {
 335       apply_pragma_weak (decl, value);
 336       if (value)
 337         assemble_alias (decl, value);
 338     }
 339   else
 340     pending_weaks = tree_cons (name, value, pending_weaks);
 341 }
 342 #else
 343 void
 344 maybe_apply_pragma_weak (decl)
 345      tree decl ATTRIBUTE_UNUSED;
 346 {
 347 }
 348 #endif /* HANDLE_PRAGMA_WEAK */
 349
 350 static GTY(()) tree pending_redefine_extname;
 351
 352 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 353 static void handle_pragma_redefine_extname PARAMS ((cpp_reader *));
 354
 355 /* #pragma redefined_extname oldname newname */
 356 static void
 357 handle_pragma_redefine_extname (dummy)
 358      cpp_reader *dummy ATTRIBUTE_UNUSED;
 359 {
 360   tree oldname, newname, decl, x;
 361   enum cpp_ttype t;
 362
 363   if (c_lex (&oldname) != CPP_NAME)
 364     {
 365       warning ("malformed #pragma redefine_extname, ignored");
 366       return;
 367     }
 368   if (c_lex (&newname) != CPP_NAME)
 369     {
 370       warning ("malformed #pragma redefine_extname, ignored");
 371       return;
 372     }
 373   t = c_lex (&x);
 374   if (t != CPP_EOF)
 375     warning ("junk at end of #pragma redefine_extname");
 376
 377   decl = identifier_global_value (oldname);
 378   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 379     {
 380       if (DECL_ASSEMBLER_NAME_SET_P (decl)
 381           && DECL_ASSEMBLER_NAME (decl) != newname)
 382         warning ("#pragma redefine_extname conflicts with declaration");
 383       SET_DECL_ASSEMBLER_NAME (decl, newname);
 384     }
 385   else
 386     add_to_renaming_pragma_list(oldname, newname);
 387 }
 388 #endif
 389
 390 void
 391 add_to_renaming_pragma_list (oldname, newname)
 392         tree oldname, newname;
 393 {
 394   pending_redefine_extname
 395     = tree_cons (oldname, newname, pending_redefine_extname);
 396 }
 397
 398 static GTY(()) tree pragma_extern_prefix;
 399
 400 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 401 static void handle_pragma_extern_prefix PARAMS ((cpp_reader *));
 402
 403 /* #pragma extern_prefix "prefix" */
 404 static void
 405 handle_pragma_extern_prefix (dummy)
 406      cpp_reader *dummy ATTRIBUTE_UNUSED;
 407 {
 408   tree prefix, x;
 409   enum cpp_ttype t;
 410
 411   if (c_lex (&prefix) != CPP_STRING)
 412     {
 413       warning ("malformed #pragma extern_prefix, ignored");
 414       return;
 415     }
 416   t = c_lex (&x);
 417   if (t != CPP_EOF)
 418     warning ("junk at end of #pragma extern_prefix");
 419
 420   /* Note that the length includes the null terminator.  */
 421   pragma_extern_prefix = (TREE_STRING_LENGTH (prefix) > 1 ? prefix : NULL);
 422 }
 423 #endif
 424
 425 /* Hook from the front ends to apply the results of one of the preceeding
 426    pragmas that rename variables.  */
 427
 428 tree
 429 maybe_apply_renaming_pragma (decl, asmname)
 430      tree decl, asmname;
 431 {
 432   tree oldname;
 433
 434   /* Copied from the check in set_decl_assembler_name.  */
 435   if (TREE_CODE (decl) == FUNCTION_DECL
 436       || (TREE_CODE (decl) == VAR_DECL
 437           && (TREE_STATIC (decl)
 438               || DECL_EXTERNAL (decl)
 439               || TREE_PUBLIC (decl))))
 440     oldname = DECL_ASSEMBLER_NAME (decl);
 441   else
 442     return asmname;
 443
 444   /* If the name begins with a *, that's a sign of an asmname attached to
 445      a previous declaration.  */
 446   if (IDENTIFIER_POINTER (oldname)[0] == '*')
 447     {
 448       const char *oldasmname = IDENTIFIER_POINTER (oldname) + 1;
 449       if (asmname && strcmp (TREE_STRING_POINTER (asmname), oldasmname) != 0)
 450         warning ("asm declaration conficts with previous rename");
 451       asmname = build_string (strlen (oldasmname), oldasmname);
 452     }
 453
 454   {
 455     tree *p, t;
 456
 457     for (p = &pending_redefine_extname; (t = *p) ; p = &TREE_CHAIN (t))
 458       if (oldname == TREE_PURPOSE (t))
 459         {
 460           const char *newname = IDENTIFIER_POINTER (TREE_VALUE (t));
 461
 462           if (asmname && strcmp (TREE_STRING_POINTER (asmname), newname) != 0)
 463             warning ("#pragma redefine_extname conflicts with declaration");
 464           *p = TREE_CHAIN (t);
 465
 466           return build_string (strlen (newname), newname);
 467         }
 468   }
 469
 470 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 471   if (pragma_extern_prefix && !asmname)
 472     {
 473       char *x = concat (TREE_STRING_POINTER (pragma_extern_prefix),
 474                         IDENTIFIER_POINTER (oldname), NULL);
 475       asmname = build_string (strlen (x), x);
 476       free (x);
 477       return asmname;
 478     }
 479 #endif
 480
 481   return asmname;
 482 }
 483
 484 void
 485 init_pragma ()
 486 {
 487 #ifdef HANDLE_PRAGMA_PACK
 488   cpp_register_pragma (parse_in, 0, "pack", handle_pragma_pack);
 489 #endif
 490 #ifdef HANDLE_PRAGMA_WEAK
 491   cpp_register_pragma (parse_in, 0, "weak", handle_pragma_weak);
 492 #endif
 493 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 494   cpp_register_pragma (parse_in, 0, "redefine_extname",
 495                        handle_pragma_redefine_extname);
 496 #endif
 497 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 498   cpp_register_pragma (parse_in, 0, "extern_prefix",
 499                        handle_pragma_extern_prefix);
 500 #endif
 501
 502 #ifdef REGISTER_TARGET_PRAGMAS
 503   REGISTER_TARGET_PRAGMAS (parse_in);
 504 #endif
 505 }
 506
 507 #include "gt-c-pragma.h"