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-lex.h"
  33 #include "c-common.h"
  34 #include "output.h"
  35 #include "tm_p.h"
  36
  37 #define GCC_BAD(msgid) do { warning (msgid); return; } while (0)
  38 #define GCC_BAD2(msgid, arg) do { warning (msgid, arg); return; } while (0)
  39
  40 #ifdef HANDLE_PRAGMA_PACK
  41 static void handle_pragma_pack PARAMS ((cpp_reader *));
  42
  43 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
  44 typedef struct align_stack
  45 {
  46   int                  alignment;
  47   unsigned int         num_pushes;
  48   tree                 id;
  49   struct align_stack * prev;
  50 } align_stack;
  51
  52 static struct align_stack * alignment_stack = NULL;
  53
  54 /* If we have a "global" #pragma pack(<n>) in effect when the first
  55    #pragma pack(push,<n>) is encountered, this stores the value of
  56    maximum_field_alignment in effect.  When the final pop_alignment()
  57    happens, we restore the value to this, not to a value of 0 for
  58    maximum_field_alignment.  Value is in bits.  */
  59 static int default_alignment;
  60 #define SET_GLOBAL_ALIGNMENT(ALIGN) \
  61   (default_alignment = maximum_field_alignment = (ALIGN))
  62
  63 static void push_alignment PARAMS ((int, tree));
  64 static void pop_alignment  PARAMS ((tree));
  65 static void mark_align_stack PARAMS ((void *));
  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 *) xmalloc (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       free (alignment_stack);
 142
 143       alignment_stack = entry;
 144     }
 145 }
 146
 147 static void
 148 mark_align_stack (p)
 149     void *p;
 150 {
 151   align_stack *a = *(align_stack **) p;
 152
 153   while (a)
 154     {
 155       ggc_mark_tree (a->id);
 156       a = a->prev;
 157     }
 158 }
 159 #else  /* not HANDLE_PRAGMA_PACK_PUSH_POP */
 160 #define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
 161 #define push_alignment(ID, N) \
 162     GCC_BAD("#pragma pack(push[, id], <n>) is not supported on this target")
 163 #define pop_alignment(ID) \
 164     GCC_BAD("#pragma pack(pop[, id], <n>) is not supported on this target")
 165 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 166
 167 /* #pragma pack ()
 168    #pragma pack (N)
 169
 170    #pragma pack (push, N)
 171    #pragma pack (push, ID, N)
 172    #pragma pack (pop)
 173    #pragma pack (pop, ID) */
 174 static void
 175 handle_pragma_pack (dummy)
 176      cpp_reader *dummy ATTRIBUTE_UNUSED;
 177 {
 178   tree x, id = 0;
 179   int align = -1;
 180   enum cpp_ttype token;
 181   enum { set, push, pop } action;
 182
 183   if (c_lex (&x) != CPP_OPEN_PAREN)
 184     GCC_BAD ("missing '(' after '#pragma pack' - ignored");
 185
 186   token = c_lex (&x);
 187   if (token == CPP_CLOSE_PAREN)
 188     {
 189       action = set;
 190       align = 0;
 191     }
 192   else if (token == CPP_NUMBER)
 193     {
 194       align = TREE_INT_CST_LOW (x);
 195       action = set;
 196       if (c_lex (&x) != CPP_CLOSE_PAREN)
 197         GCC_BAD ("malformed '#pragma pack' - ignored");
 198     }
 199   else if (token == CPP_NAME)
 200     {
 201 #define GCC_BAD_ACTION do { if (action == push) \
 202           GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
 203         else \
 204           GCC_BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
 205         } while (0)
 206
 207       const char *op = IDENTIFIER_POINTER (x);
 208       if (!strcmp (op, "push"))
 209         action = push;
 210       else if (!strcmp (op, "pop"))
 211         action = pop;
 212       else
 213         GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
 214
 215       token = c_lex (&x);
 216       if (token != CPP_COMMA && action == push)
 217         GCC_BAD_ACTION;
 218
 219       if (token == CPP_COMMA)
 220         {
 221           token = c_lex (&x);
 222           if (token == CPP_NAME)
 223             {
 224               id = x;
 225               if (action == push && c_lex (&x) != CPP_COMMA)
 226                 GCC_BAD_ACTION;
 227               token = c_lex (&x);
 228             }
 229
 230           if (action == push)
 231             {
 232               if (token == CPP_NUMBER)
 233                 {
 234                   align = TREE_INT_CST_LOW (x);
 235                   token = c_lex (&x);
 236                 }
 237               else
 238                 GCC_BAD_ACTION;
 239             }
 240         }
 241
 242       if (token != CPP_CLOSE_PAREN)
 243         GCC_BAD_ACTION;
 244 #undef GCC_BAD_ACTION
 245     }
 246   else
 247     GCC_BAD ("malformed '#pragma pack' - ignored");
 248
 249   if (c_lex (&x) != CPP_EOF)
 250     warning ("junk at end of '#pragma pack'");
 251
 252   if (action != pop)
 253     switch (align)
 254       {
 255       case 0:
 256       case 1:
 257       case 2:
 258       case 4:
 259       case 8:
 260       case 16:
 261         align *= BITS_PER_UNIT;
 262         break;
 263       default:
 264         GCC_BAD2 ("alignment must be a small power of two, not %d", align);
 265       }
 266
 267   switch (action)
 268     {
 269     case set:   SET_GLOBAL_ALIGNMENT (align);  break;
 270     case push:  push_alignment (align, id);    break;
 271     case pop:   pop_alignment (id);            break;
 272     }
 273 }
 274 #endif  /* HANDLE_PRAGMA_PACK */
 275
 276 #ifdef HANDLE_PRAGMA_WEAK
 277 static void apply_pragma_weak PARAMS ((tree, tree));
 278 static void handle_pragma_weak PARAMS ((cpp_reader *));
 279
 280 static tree pending_weaks;
 281
 282 static void
 283 apply_pragma_weak (decl, value)
 284      tree decl, value;
 285 {
 286   if (value)
 287     {
 288       value = build_string (IDENTIFIER_LENGTH (value),
 289                             IDENTIFIER_POINTER (value));
 290       decl_attributes (&decl, build_tree_list (get_identifier ("alias"),
 291                                                build_tree_list (NULL, value)),
 292                        0);
 293     }
 294
 295   if (SUPPORTS_WEAK && DECL_EXTERNAL (decl) && TREE_USED (decl)
 296       && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
 297     warning_with_decl (decl, "applying #pragma weak `%s' after first use results in unspecified behavior");
 298
 299   declare_weak (decl);
 300 }
 301
 302 void
 303 maybe_apply_pragma_weak (decl)
 304      tree decl;
 305 {
 306   tree *p, t, id;
 307
 308   /* Copied from the check in set_decl_assembler_name.  */
 309   if (TREE_CODE (decl) == FUNCTION_DECL
 310       || (TREE_CODE (decl) == VAR_DECL
 311           && (TREE_STATIC (decl)
 312               || DECL_EXTERNAL (decl)
 313               || TREE_PUBLIC (decl))))
 314     id = DECL_ASSEMBLER_NAME (decl);
 315   else
 316     return;
 317
 318   for (p = &pending_weaks; (t = *p) ; p = &TREE_CHAIN (t))
 319     if (id == TREE_PURPOSE (t))
 320       {
 321         apply_pragma_weak (decl, TREE_VALUE (t));
 322         *p = TREE_CHAIN (t);
 323         break;
 324       }
 325 }
 326
 327 /* #pragma weak name [= value] */
 328 static void
 329 handle_pragma_weak (dummy)
 330      cpp_reader *dummy ATTRIBUTE_UNUSED;
 331 {
 332   tree name, value, x, decl;
 333   enum cpp_ttype t;
 334
 335   value = 0;
 336
 337   if (c_lex (&name) != CPP_NAME)
 338     GCC_BAD ("malformed #pragma weak, ignored");
 339   t = c_lex (&x);
 340   if (t == CPP_EQ)
 341     {
 342       if (c_lex (&value) != CPP_NAME)
 343         GCC_BAD ("malformed #pragma weak, ignored");
 344       t = c_lex (&x);
 345     }
 346   if (t != CPP_EOF)
 347     warning ("junk at end of #pragma weak");
 348
 349   decl = identifier_global_value (name);
 350   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 351     {
 352       apply_pragma_weak (decl, value);
 353       if (value)
 354         assemble_alias (decl, value);
 355     }
 356   else
 357     pending_weaks = tree_cons (name, value, pending_weaks);
 358 }
 359 #else
 360 void
 361 maybe_apply_pragma_weak (decl)
 362      tree decl ATTRIBUTE_UNUSED;
 363 {
 364 }
 365 #endif /* HANDLE_PRAGMA_WEAK */
 366
 367 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 368 static void handle_pragma_redefine_extname PARAMS ((cpp_reader *));
 369
 370 static tree pending_redefine_extname;
 371
 372 /* #pragma redefined_extname oldname newname */
 373 static void
 374 handle_pragma_redefine_extname (dummy)
 375      cpp_reader *dummy ATTRIBUTE_UNUSED;
 376 {
 377   tree oldname, newname, decl, x;
 378   enum cpp_ttype t;
 379
 380   if (c_lex (&oldname) != CPP_NAME)
 381     {
 382       warning ("malformed #pragma redefine_extname, ignored");
 383       return;
 384     }
 385   if (c_lex (&newname) != CPP_NAME)
 386     {
 387       warning ("malformed #pragma redefine_extname, ignored");
 388       return;
 389     }
 390   t = c_lex (&x);
 391   if (t != CPP_EOF)
 392     warning ("junk at end of #pragma redefine_extname");
 393
 394   decl = identifier_global_value (oldname);
 395   if (decl && TREE_CODE_CLASS (TREE_CODE (decl)) == 'd')
 396     {
 397       if (DECL_ASSEMBLER_NAME_SET_P (decl)
 398           && DECL_ASSEMBLER_NAME (decl) != newname)
 399         warning ("#pragma redefine_extname conflicts with declaration");
 400       SET_DECL_ASSEMBLER_NAME (decl, newname);
 401     }
 402   else
 403     pending_redefine_extname
 404       = tree_cons (oldname, newname, pending_redefine_extname);
 405 }
 406 #endif
 407
 408 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 409 static void handle_pragma_extern_prefix PARAMS ((cpp_reader *));
 410
 411 static tree pragma_extern_prefix;
 412
 413 /* #pragma extern_prefix "prefix" */
 414 static void
 415 handle_pragma_extern_prefix (dummy)
 416      cpp_reader *dummy ATTRIBUTE_UNUSED;
 417 {
 418   tree prefix, x;
 419   enum cpp_ttype t;
 420
 421   if (c_lex (&prefix) != CPP_STRING)
 422     {
 423       warning ("malformed #pragma extern_prefix, ignored");
 424       return;
 425     }
 426   t = c_lex (&x);
 427   if (t != CPP_EOF)
 428     warning ("junk at end of #pragma extern_prefix");
 429
 430   /* Note that the length includes the null terminator.  */
 431   pragma_extern_prefix = (TREE_STRING_LENGTH (prefix) > 1 ? prefix : NULL);
 432 }
 433 #endif
 434
 435 /* Hook from the front ends to apply the results of one of the preceeding
 436    pragmas that rename variables.  */
 437
 438 tree
 439 maybe_apply_renaming_pragma (decl, asmname)
 440      tree decl, asmname;
 441 {
 442   tree oldname;
 443
 444   /* Copied from the check in set_decl_assembler_name.  */
 445   if (TREE_CODE (decl) == FUNCTION_DECL
 446       || (TREE_CODE (decl) == VAR_DECL
 447           && (TREE_STATIC (decl)
 448               || DECL_EXTERNAL (decl)
 449               || TREE_PUBLIC (decl))))
 450     oldname = DECL_ASSEMBLER_NAME (decl);
 451   else
 452     return asmname;
 453
 454   /* If the name begins with a *, that's a sign of an asmname attached to
 455      a previous declaration.  */
 456   if (IDENTIFIER_POINTER (oldname)[0] == '*')
 457     {
 458       const char *oldasmname = IDENTIFIER_POINTER (oldname) + 1;
 459       if (asmname && strcmp (TREE_STRING_POINTER (asmname), oldasmname) != 0)
 460         warning ("asm declaration conficts with previous rename");
 461       asmname = build_string (strlen (oldasmname), oldasmname);
 462     }
 463
 464 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 465   {
 466     tree *p, t;
 467
 468     for (p = &pending_redefine_extname; (t = *p) ; p = &TREE_CHAIN (t))
 469       if (oldname == TREE_PURPOSE (t))
 470         {
 471           const char *newname = IDENTIFIER_POINTER (TREE_VALUE (t));
 472
 473           if (asmname && strcmp (TREE_STRING_POINTER (asmname), newname) != 0)
 474             warning ("#pragma redefine_extname conflicts with declaration");
 475           *p = TREE_CHAIN (t);
 476
 477           return build_string (strlen (newname), newname);
 478         }
 479   }
 480 #endif
 481
 482 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 483   if (pragma_extern_prefix && !asmname)
 484     {
 485       char *x = concat (TREE_STRING_POINTER (pragma_extern_prefix),
 486                         IDENTIFIER_POINTER (oldname), NULL);
 487       asmname = build_string (strlen (x), x);
 488       free (x);
 489       return asmname;
 490     }
 491 #endif
 492
 493   return asmname;
 494 }
 495
 496 void
 497 init_pragma ()
 498 {
 499 #ifdef HANDLE_PRAGMA_PACK
 500   cpp_register_pragma (parse_in, 0, "pack", handle_pragma_pack);
 501 #endif
 502 #ifdef HANDLE_PRAGMA_WEAK
 503   cpp_register_pragma (parse_in, 0, "weak", handle_pragma_weak);
 504   ggc_add_tree_root (&pending_weaks, 1);
 505 #endif
 506 #ifdef HANDLE_PRAGMA_REDEFINE_EXTNAME
 507   cpp_register_pragma (parse_in, 0, "redefine_extname",
 508                        handle_pragma_redefine_extname);
 509   ggc_add_tree_root (&pending_redefine_extname, 1);
 510 #endif
 511 #ifdef HANDLE_PRAGMA_EXTERN_PREFIX
 512   cpp_register_pragma (parse_in, 0, "extern_prefix",
 513                        handle_pragma_extern_prefix);
 514   ggc_add_tree_root (&pragma_extern_prefix, 1);
 515 #endif
 516
 517 #ifdef REGISTER_TARGET_PRAGMAS
 518   REGISTER_TARGET_PRAGMAS (parse_in);
 519 #endif
 520
 521 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
 522   ggc_add_root (&alignment_stack, 1, sizeof(alignment_stack),
 523                 mark_align_stack);
 524 #endif
 525 }