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 PARAMS ((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 PARAMS ((int, tree));
  65 static void pop_alignment  PARAMS ((tree));
  66
  67 /* Push an alignment value onto the stack.  */
  68 static void
  69 push_alignment (alignment, id)
  70      int alignment;
  71      tree id;
  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 *) ggc_alloc (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       alignment_stack = entry;
 142     }
 143 }
 144 #else  /* not HANDLE_PRAGMA_PACK_PUSH_POP */
 145 #define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
 146 #define push_alignment(ID, N) \
 147     GCC_BAD("#pragma pack(push[, id], <n>) is not supported on this target")
 148 #define pop_alignment(ID) \
 149     GCC_BAD("#pragma pack(pop[, id], <n>) is not supported on this target")
 150 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 151
 152 /* #pragma pack ()
 153    #pragma pack (N)
 154
 155    #pragma pack (push, N)
 156    #pragma pack (push, ID, N)
 157    #pragma pack (pop)
 158    #pragma pack (pop, ID) */
 159 static void
 160 handle_pragma_pack (dummy)
 161      cpp_reader *dummy ATTRIBUTE_UNUSED;
 162 {
 163   tree x, id = 0;
 164   int align = -1;
 165   enum cpp_ttype token;
 166   enum { set, push, pop } action;
 167
 168   if (c_lex (&x) != CPP_OPEN_PAREN)
 169     GCC_BAD ("missing '(' after '#pragma pack' - ignored");
 170
 171   token = c_lex (&x);
 172   if (token == CPP_CLOSE_PAREN)
 173     {
 174       action = set;
 175       align = 0;
 176     }
 177   else if (token == CPP_NUMBER)
 178     {
 179       align = TREE_INT_CST_LOW (x);
 180       action = set;
 181       if (c_lex (&x) != CPP_CLOSE_PAREN)
 182         GCC_BAD ("malformed '#pragma pack' - ignored");
 183     }
 184   else if (token == CPP_NAME)
 185     {
 186 #define GCC_BAD_ACTION do { if (action == push) \
 187           GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
 188         else \
 189           GCC_BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
 190         } while (0)
 191
 192       const char *op = IDENTIFIER_POINTER (x);
 193       if (!strcmp (op, "push"))
 194         action = push;
 195       else if (!strcmp (op, "pop"))
 196         action = pop;
 197       else
 198         GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
 199
 200       token = c_lex (&x);
 201       if (token != CPP_COMMA && action == push)
 202         GCC_BAD_ACTION;
 203
 204       if (token == CPP_COMMA)
 205         {
 206           token = c_lex (&x);
 207           if (token == CPP_NAME)
 208             {
 209               id = x;
 210               if (action == push && c_lex (&x) != CPP_COMMA)
 211                 GCC_BAD_ACTION;
 212               token = c_lex (&x);
 213             }
 214
 215           if (action == push)
 216             {
 217               if (token == CPP_NUMBER)
 218                 {
 219                   align = TREE_INT_CST_LOW (x);
 220                   token = c_lex (&x);
 221                 }
 222               else
 223                 GCC_BAD_ACTION;
 224             }
 225         }
 226
 227       if (token != CPP_CLOSE_PAREN)
 228         GCC_BAD_ACTION;
 229 #undef GCC_BAD_ACTION
 230     }
 231   else
 232     GCC_BAD ("malformed '#pragma pack' - ignored");
 233
 234   if (c_lex (&x) != CPP_EOF)
 235     warning ("junk at end of '#pragma pack'");
 236
 237   if (action != pop)
 238     switch (align)
 239       {
 240       case 0:
 241       case 1:
 242       case 2:
 243       case 4:
 244       case 8:
 245       case 16:
 246         align *= BITS_PER_UNIT;
 247         break;
 248       default:
 249         GCC_BAD2 ("alignment must be a small power of two, not %d", align);
 250       }
 251
 252   switch (action)
 253     {
 254     case set:   SET_GLOBAL_ALIGNMENT (align);  break;
 255     case push:  push_alignment (align, id);    break;
 256     case pop:   pop_alignment (id);            break;
 257     }
 258 }
 259 #endif  /* HANDLE_PRAGMA_PACK */
 260
 261 static GTY(()) tree pending_weaks;
 262
 263 #ifdef HANDLE_PRAGMA_WEAK
 264 static void apply_pragma_weak PARAMS ((tree, tree));
 265 static void handle_pragma_weak PARAMS ((cpp_reader *));
 266
 267 static void
 268 apply_pragma_weak (decl, value)
 269      tree decl, value;
 270 {
 271   if (value)
 272     {
 273       value = build_string (IDENTIFIER_LENGTH (value),
 274                             IDENTIFIER_POINTER (value));
 275       decl_attributes (&decl, build_tree_list (get_identifier ("alias"),
 276                                                build_tree_list (NULL, value)),
 277                        0);
 278     }
 279
 280   if (SUPPORTS_WEAK && DECL_EXTERNAL (decl) && TREE_USED (decl)
 281       && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
 282     warning_with_decl (decl, "applying #pragma weak `%s' after first use results in unspecified behavior");
 283
 284   declare_weak (decl);
 285 }
 286
 287 void
 288 maybe_apply_pragma_weak (decl)
 289      tree decl;
 290 {
 291   tree *p, t, id;
 292
 293   /* Copied from the check in set_decl_assembler_name.  */
 294   if (TREE_CODE (decl) == FUNCTION_DECL
 295       || (TREE_CODE (decl) == VAR_DECL
 296           && (TREE_STATIC (decl)
 297               || DECL_EXTERNAL (decl)
 298               || TREE_PUBLIC (decl))))
 299     id = DECL_ASSEMBLER_NAME (decl);
 300   else
 301     return;
 302
 303   for (p = &pending_weaks; (t = *p) ; p = &TREE_CHAIN (t))
 304     if (id == TREE_PURPOSE (t))
 305       {
 306         apply_pragma_weak (decl, TREE_VALUE (t));
 307         *p = TREE_CHAIN (t);
 308         break;
 309       }
 310 }
 311
 312 /* #pragma weak name [= value] */
 313 static void
 314 handle_pragma_weak (dummy)
 315      cpp_reader *dummy ATTRIBUTE_UNUSED;
 316 {
 317   tree name, value, x, decl;
 318   enum cpp_ttype t;
 319
 320   value = 0;
 321
 322   if (c_lex (&name) != CPP_NAME)
 323     GCC_BAD ("malformed #pragma weak, ignored");
 324   t = c_lex (&x);
 325   if (t == CPP_EQ)
 326     {
 327       if (c_lex (&value) != CPP_NAME)
 328         GCC_BAD ("malformed #pragma weak, ignored");
 329       t = c_lex (&x);
 330     }
 331   if (t != CPP_EOF)
 332     warning ("junk at end of #pragma weak");
 333
 334   decl = identifier_global_value (name);
 335   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 336     {
 337       apply_pragma_weak (decl, value);
 338       if (value)
 339         assemble_alias (decl, value);
 340     }
 341   else
 342     pending_weaks = tree_cons (name, value, pending_weaks);
 343 }
 344 #else
 345 void
 346 maybe_apply_pragma_weak (decl)
 347      tree decl ATTRIBUTE_UNUSED;
 348 {
 349 }
 350 #endif /* HANDLE_PRAGMA_WEAK */
 351
 352 static GTY(()) tree pending_redefine_extname;
 353
 354 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 355 static void handle_pragma_redefine_extname PARAMS ((cpp_reader *));
 356
 357 /* #pragma redefined_extname oldname newname */
 358 static void
 359 handle_pragma_redefine_extname (dummy)
 360      cpp_reader *dummy ATTRIBUTE_UNUSED;
 361 {
 362   tree oldname, newname, decl, x;
 363   enum cpp_ttype t;
 364
 365   if (c_lex (&oldname) != CPP_NAME)
 366     {
 367       warning ("malformed #pragma redefine_extname, ignored");
 368       return;
 369     }
 370   if (c_lex (&newname) != CPP_NAME)
 371     {
 372       warning ("malformed #pragma redefine_extname, ignored");
 373       return;
 374     }
 375   t = c_lex (&x);
 376   if (t != CPP_EOF)
 377     warning ("junk at end of #pragma redefine_extname");
 378
 379   decl = identifier_global_value (oldname);
 380   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 381     {
 382       if (DECL_ASSEMBLER_NAME_SET_P (decl)
 383           && DECL_ASSEMBLER_NAME (decl) != newname)
 384         warning ("#pragma redefine_extname conflicts with declaration");
 385       SET_DECL_ASSEMBLER_NAME (decl, newname);
 386     }
 387   else
 388     add_to_renaming_pragma_list(oldname, newname);
 389 }
 390 #endif
 391
 392 void
 393 add_to_renaming_pragma_list (oldname, newname)
 394         tree oldname, newname;
 395 {
 396   pending_redefine_extname
 397     = tree_cons (oldname, newname, pending_redefine_extname);
 398 }
 399
 400 static GTY(()) tree pragma_extern_prefix;
 401
 402 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 403 static void handle_pragma_extern_prefix PARAMS ((cpp_reader *));
 404
 405 /* #pragma extern_prefix "prefix" */
 406 static void
 407 handle_pragma_extern_prefix (dummy)
 408      cpp_reader *dummy ATTRIBUTE_UNUSED;
 409 {
 410   tree prefix, x;
 411   enum cpp_ttype t;
 412
 413   if (c_lex (&prefix) != CPP_STRING)
 414     {
 415       warning ("malformed #pragma extern_prefix, ignored");
 416       return;
 417     }
 418   t = c_lex (&x);
 419   if (t != CPP_EOF)
 420     warning ("junk at end of #pragma extern_prefix");
 421
 422   /* Note that the length includes the null terminator.  */
 423   pragma_extern_prefix = (TREE_STRING_LENGTH (prefix) > 1 ? prefix : NULL);
 424 }
 425 #endif
 426
 427 /* Hook from the front ends to apply the results of one of the preceding
 428    pragmas that rename variables.  */
 429
 430 tree
 431 maybe_apply_renaming_pragma (decl, asmname)
 432      tree decl, asmname;
 433 {
 434   tree oldname;
 435
 436   /* Copied from the check in set_decl_assembler_name.  */
 437   if (TREE_CODE (decl) == FUNCTION_DECL
 438       || (TREE_CODE (decl) == VAR_DECL
 439           && (TREE_STATIC (decl)
 440               || DECL_EXTERNAL (decl)
 441               || TREE_PUBLIC (decl))))
 442     oldname = DECL_ASSEMBLER_NAME (decl);
 443   else
 444     return asmname;
 445
 446   /* If the name begins with a *, that's a sign of an asmname attached to
 447      a previous declaration.  */
 448   if (IDENTIFIER_POINTER (oldname)[0] == '*')
 449     {
 450       const char *oldasmname = IDENTIFIER_POINTER (oldname) + 1;
 451       if (asmname && strcmp (TREE_STRING_POINTER (asmname), oldasmname) != 0)
 452         warning ("asm declaration conficts with previous rename");
 453       asmname = build_string (strlen (oldasmname), oldasmname);
 454     }
 455
 456   {
 457     tree *p, t;
 458
 459     for (p = &pending_redefine_extname; (t = *p) ; p = &TREE_CHAIN (t))
 460       if (oldname == TREE_PURPOSE (t))
 461         {
 462           const char *newname = IDENTIFIER_POINTER (TREE_VALUE (t));
 463
 464           if (asmname && strcmp (TREE_STRING_POINTER (asmname), newname) != 0)
 465             warning ("#pragma redefine_extname conflicts with declaration");
 466           *p = TREE_CHAIN (t);
 467
 468           return build_string (strlen (newname), newname);
 469         }
 470   }
 471
 472 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 473   if (pragma_extern_prefix && !asmname)
 474     {
 475       char *x = concat (TREE_STRING_POINTER (pragma_extern_prefix),
 476                         IDENTIFIER_POINTER (oldname), NULL);
 477       asmname = build_string (strlen (x), x);
 478       free (x);
 479       return asmname;
 480     }
 481 #endif
 482
 483   return asmname;
 484 }
 485
 486 /* Front-end wrapper for pragma registration to avoid dragging
 487    cpplib.h in almost everywhere.  */
 488 void
 489 c_register_pragma (space, name, handler)
 490      const char *space;
 491      const char *name;
 492      void (*handler) PARAMS ((struct cpp_reader *));
 493 {
 494   cpp_register_pragma (parse_in, space, name, handler);
 495 }
 496
 497 /* Set up front-end pragmas.  */
 498 void
 499 init_pragma ()
 500 {
 501 #ifdef HANDLE_PRAGMA_PACK
 502   c_register_pragma (0, "pack", handle_pragma_pack);
 503 #endif
 504 #ifdef HANDLE_PRAGMA_WEAK
 505   c_register_pragma (0, "weak", handle_pragma_weak);
 506 #endif
 507 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 508   c_register_pragma (0, "redefine_extname", handle_pragma_redefine_extname);
 509 #endif
 510 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 511   c_register_pragma (0, "extern_prefix", handle_pragma_extern_prefix);
 512 #endif
 513
 514 #ifdef REGISTER_TARGET_PRAGMAS
 515   REGISTER_TARGET_PRAGMAS ();
 516 #endif
 517 }
 518
 519 #include "gt-c-pragma.h"