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 = 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       && !DECL_WEAK (decl) /* don't complain about a redundant #pragma */
 277       && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
 278     warning ("%Japplying #pragma weak '%D' after first use results "
 279              "in unspecified behavior", decl, decl);
 280
 281   declare_weak (decl);
 282 }
 283
 284 void
 285 maybe_apply_pragma_weak (tree decl)
 286 {
 287   tree *p, t, id;
 288
 289   /* Avoid asking for DECL_ASSEMBLER_NAME when it's not needed.  */
 290
 291   /* No weak symbols pending, take the short-cut.  */
 292   if (!pending_weaks)
 293     return;
 294   /* If it's not visible outside this file, it doesn't matter whether
 295      it's weak.  */
 296   if (!DECL_EXTERNAL (decl) && !TREE_PUBLIC (decl))
 297     return;
 298   /* If it's not a function or a variable, it can't be weak.
 299      FIXME: what kinds of things are visible outside this file but
 300      aren't functions or variables?   Should this be an abort() instead?  */
 301   if (TREE_CODE (decl) != FUNCTION_DECL && TREE_CODE (decl) != VAR_DECL)
 302     return;
 303
 304   id = DECL_ASSEMBLER_NAME (decl);
 305
 306   for (p = &pending_weaks; (t = *p) ; p = &TREE_CHAIN (t))
 307     if (id == TREE_PURPOSE (t))
 308       {
 309         apply_pragma_weak (decl, TREE_VALUE (t));
 310         *p = TREE_CHAIN (t);
 311         break;
 312       }
 313 }
 314
 315 /* #pragma weak name [= value] */
 316 static void
 317 handle_pragma_weak (cpp_reader *dummy ATTRIBUTE_UNUSED)
 318 {
 319   tree name, value, x, decl;
 320   enum cpp_ttype t;
 321
 322   value = 0;
 323
 324   if (c_lex (&name) != CPP_NAME)
 325     GCC_BAD ("malformed #pragma weak, ignored");
 326   t = c_lex (&x);
 327   if (t == CPP_EQ)
 328     {
 329       if (c_lex (&value) != CPP_NAME)
 330         GCC_BAD ("malformed #pragma weak, ignored");
 331       t = c_lex (&x);
 332     }
 333   if (t != CPP_EOF)
 334     warning ("junk at end of #pragma weak");
 335
 336   decl = identifier_global_value (name);
 337   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 338     {
 339       apply_pragma_weak (decl, value);
 340       if (value)
 341         assemble_alias (decl, value);
 342     }
 343   else
 344     pending_weaks = tree_cons (name, value, pending_weaks);
 345 }
 346 #else
 347 void
 348 maybe_apply_pragma_weak (tree decl ATTRIBUTE_UNUSED)
 349 {
 350 }
 351 #endif /* HANDLE_PRAGMA_WEAK */
 352
 353 static GTY(()) tree pending_redefine_extname;
 354
 355 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 356 static void handle_pragma_redefine_extname (cpp_reader *);
 357
 358 /* #pragma redefined_extname oldname newname */
 359 static void
 360 handle_pragma_redefine_extname (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       change_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 (tree oldname, tree newname)
 394 {
 395   pending_redefine_extname
 396     = tree_cons (oldname, newname, pending_redefine_extname);
 397 }
 398
 399 static GTY(()) tree pragma_extern_prefix;
 400
 401 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 402 static void handle_pragma_extern_prefix (cpp_reader *);
 403
 404 /* #pragma extern_prefix "prefix" */
 405 static void
 406 handle_pragma_extern_prefix (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 preceding
 426    pragmas that rename variables.  */
 427
 428 tree
 429 maybe_apply_renaming_pragma (tree decl, tree asmname)
 430 {
 431   tree oldname;
 432
 433   /* Copied from the check in set_decl_assembler_name.  */
 434   if (TREE_CODE (decl) == FUNCTION_DECL
 435       || (TREE_CODE (decl) == VAR_DECL
 436           && (TREE_STATIC (decl)
 437               || DECL_EXTERNAL (decl)
 438               || TREE_PUBLIC (decl))))
 439     oldname = DECL_ASSEMBLER_NAME (decl);
 440   else
 441     return asmname;
 442
 443   /* If the name begins with a *, that's a sign of an asmname attached to
 444      a previous declaration.  */
 445   if (IDENTIFIER_POINTER (oldname)[0] == '*')
 446     {
 447       const char *oldasmname = IDENTIFIER_POINTER (oldname) + 1;
 448       if (asmname && strcmp (TREE_STRING_POINTER (asmname), oldasmname) != 0)
 449         warning ("asm declaration conflicts with previous rename");
 450       asmname = build_string (strlen (oldasmname), oldasmname);
 451     }
 452
 453   {
 454     tree *p, t;
 455
 456     for (p = &pending_redefine_extname; (t = *p) ; p = &TREE_CHAIN (t))
 457       if (oldname == TREE_PURPOSE (t))
 458         {
 459           const char *newname = IDENTIFIER_POINTER (TREE_VALUE (t));
 460
 461           if (asmname && strcmp (TREE_STRING_POINTER (asmname), newname) != 0)
 462             warning ("#pragma redefine_extname conflicts with declaration");
 463           *p = TREE_CHAIN (t);
 464
 465           return build_string (strlen (newname), newname);
 466         }
 467   }
 468
 469 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 470   if (pragma_extern_prefix && !asmname)
 471     {
 472       char *x = concat (TREE_STRING_POINTER (pragma_extern_prefix),
 473                         IDENTIFIER_POINTER (oldname), NULL);
 474       asmname = build_string (strlen (x), x);
 475       free (x);
 476       return asmname;
 477     }
 478 #endif
 479
 480   return asmname;
 481 }
 482
 483 /* Front-end wrapper for pragma registration to avoid dragging
 484    cpplib.h in almost everywhere.  */
 485 void
 486 c_register_pragma (const char *space, const char *name,
 487                    void (*handler) (struct cpp_reader *))
 488 {
 489   cpp_register_pragma (parse_in, space, name, handler);
 490 }
 491
 492 /* Set up front-end pragmas.  */
 493 void
 494 init_pragma (void)
 495 {
 496 #ifdef HANDLE_PRAGMA_PACK
 497   c_register_pragma (0, "pack", handle_pragma_pack);
 498 #endif
 499 #ifdef HANDLE_PRAGMA_WEAK
 500   c_register_pragma (0, "weak", handle_pragma_weak);
 501 #endif
 502 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 503   c_register_pragma (0, "redefine_extname", handle_pragma_redefine_extname);
 504 #endif
 505 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 506   c_register_pragma (0, "extern_prefix", handle_pragma_extern_prefix);
 507 #endif
 508
 509 #ifdef REGISTER_TARGET_PRAGMAS
 510   REGISTER_TARGET_PRAGMAS ();
 511 #endif
 512 }
 513
 514 #include "gt-c-pragma.h"