gcc/c-pragma.c

   1 /* Handle #pragma, system V.4 style.  Supports #pragma weak and #pragma pack.
   2    Copyright (C) 1992, 1997, 1998, 1999 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "rtl.h"
  24 #include "tree.h"
  25 #include "function.h"
  26 #include "defaults.h"
  27 #include "c-pragma.h"
  28 #include "flags.h"
  29 #include "toplev.h"
  30
  31 #ifdef HANDLE_GENERIC_PRAGMAS
  32
  33 #ifdef HANDLE_PRAGMA_PACK
  34 /* When structure field packing is in effect, this variable is the
  35    number of bits to use as the maximum alignment.  When packing is not
  36    in effect, this is zero.  */
  37
  38 extern int maximum_field_alignment;
  39 #endif
  40
  41
  42 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
  43 typedef struct align_stack
  44 {
  45   int                  alignment;
  46   unsigned int         num_pushes;
  47   tree                 id;
  48   struct align_stack * prev;
  49 } align_stack;
  50
  51 static struct align_stack * alignment_stack = NULL;
  52
  53 static int  push_alignment PROTO((int, tree));
  54 static int  pop_alignment  PROTO((tree));
  55
  56 /* Push an alignment value onto the stack.  */
  57 static int
  58 push_alignment (alignment, id)
  59      int alignment;
  60      tree id;
  61 {
  62   switch (alignment)
  63     {
  64     case 0:
  65     case 1:
  66     case 2:
  67     case 4:
  68     case 8:
  69     case 16:
  70       break;
  71     default:
  72       warning ("\
  73 Alignment must be a small power of two, not %d, in #pragma pack",
  74                alignment);
  75       return 0;
  76     }
  77
  78   if (alignment_stack == NULL
  79       || alignment_stack->alignment != alignment
  80       || id != NULL_TREE)
  81     {
  82       align_stack * entry;
  83
  84       entry = (align_stack *) xmalloc (sizeof (* entry));
  85
  86       if (entry == NULL)
  87         {
  88           warning ("Out of memory pushing #pragma pack");
  89           return 0;
  90         }
  91
  92       entry->alignment  = alignment;
  93       entry->num_pushes = 1;
  94       entry->id         = id;
  95       entry->prev       = alignment_stack;
  96
  97       alignment_stack = entry;
  98
  99       maximum_field_alignment = alignment * 8;
 100     }
 101   else
 102     alignment_stack->num_pushes ++;
 103
 104   return 1;
 105 }
 106
 107 /* Undo a push of an alignment onto the stack.  */
 108 static int
 109 pop_alignment (id)
 110      tree id;
 111 {
 112   align_stack * entry;
 113
 114   if (alignment_stack == NULL)
 115     {
 116       warning ("\
 117 #pragma pack (pop) encountered without matching #pragma pack (push, <n>)"
 118                );
 119       return 0;
 120     }
 121
 122   /* If we got an identifier, strip away everything above the target
 123      entry so that the next step will restore the state just below it.  */
 124   if (id)
 125     {
 126       for (entry = alignment_stack; entry; entry = entry->prev)
 127         if (entry->id == id)
 128           {
 129             entry->num_pushes = 1;
 130             alignment_stack = entry;
 131             break;
 132           }
 133       if (entry == NULL)
 134         warning ("\
 135 #pragma pack(pop, %s) encountered without matching #pragma pack(push, %s, <n>)"
 136                  , IDENTIFIER_POINTER (id), IDENTIFIER_POINTER (id));
 137     }
 138
 139   if (-- alignment_stack->num_pushes == 0)
 140     {
 141       entry = alignment_stack->prev;
 142
 143       if (entry == NULL)
 144         maximum_field_alignment = 0;
 145       else
 146         maximum_field_alignment = entry->alignment * 8;
 147
 148       free (alignment_stack);
 149
 150       alignment_stack = entry;
 151     }
 152
 153   return 1;
 154 }
 155
 156 /* Generate 'packed' and 'aligned' attributes for decls whilst a
 157    #pragma pack(push... is in effect.  */
 158 void
 159 insert_pack_attributes (node, attributes, prefix)
 160      tree node;
 161      tree * attributes;
 162      tree * prefix;
 163 {
 164   tree a;
 165   int field_alignment;
 166
 167   /* If we are not packing, then there is nothing to do.  */
 168   if (maximum_field_alignment == 0
 169       || alignment_stack == NULL)
 170     return;
 171
 172   /* We are only interested in fields.  */
 173   if (TREE_CODE_CLASS (TREE_CODE (node)) != 'd'
 174       || TREE_CODE (node) != FIELD_DECL)
 175     return;
 176
 177   field_alignment = TYPE_ALIGN (TREE_TYPE (node));
 178   if (field_alignment <= 0 || field_alignment > maximum_field_alignment)
 179     field_alignment = maximum_field_alignment;
 180
 181   /* Add a 'packed' attribute.  */
 182   * attributes = tree_cons (get_identifier ("packed"), NULL, * attributes);
 183
 184   /* If the alignment is > 8 then add an alignment attribute as well.  */
 185   if (field_alignment > 8)
 186     {
 187       /* If the aligned attribute is already present then do not override it.  */
 188       for (a = * attributes; a; a = TREE_CHAIN (a))
 189         {
 190           tree name = TREE_PURPOSE (a);
 191           if (strcmp (IDENTIFIER_POINTER (name), "aligned") == 0)
 192             break;
 193         }
 194
 195       if (a == NULL)
 196         for (a = * prefix; a; a = TREE_CHAIN (a))
 197           {
 198             tree name = TREE_PURPOSE (a);
 199             if (strcmp (IDENTIFIER_POINTER (name), "aligned") == 0)
 200               break;
 201           }
 202
 203       if (a == NULL)
 204         {
 205           * attributes = tree_cons
 206               (get_identifier ("aligned"),
 207                tree_cons (NULL,
 208                           build_int_2 (field_alignment / 8, 0),
 209                           NULL),
 210                * attributes);
 211         }
 212     }
 213
 214   return;
 215 }
 216 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 217 \f
 218 /* Handle one token of a pragma directive.  TOKEN is the current token, and
 219    STRING is its printable form.  Some front ends do not support generating
 220    tokens, and will only pass in a STRING.  Also some front ends will reuse
 221    the buffer containing STRING, so it must be copied to a local buffer if
 222    it needs to be preserved.
 223
 224    If STRING is non-NULL, then the return value will be ignored, and there
 225    will be futher calls to handle_pragma_token() in order to handle the rest of
 226    the line containing the #pragma directive.  If STRING is NULL, the entire
 227    line has now been presented to handle_pragma_token() and the return value
 228    should be zero if the pragma flawed in some way, or if the pragma was not
 229    recognised, and non-zero if it was successfully handled.  */
 230
 231 int
 232 handle_pragma_token (string, token)
 233      const char * string;
 234      tree token;
 235 {
 236   static enum pragma_state state = ps_start;
 237   static enum pragma_state type;
 238 #ifdef HANDLE_PRAGMA_WEAK
 239   static char * name;
 240   static char * value;
 241 #endif
 242 #if defined(HANDLE_PRAGMA_PACK) || defined(HANDLE_PRAGMA_PACK_PUSH_POP)
 243   static int align;
 244 #endif
 245   static tree id;
 246
 247   /* If we have reached the end of the #pragma directive then
 248      determine what value we should return.  */
 249
 250   if (string == NULL)
 251     {
 252       int ret_val = 0;
 253
 254       switch (type)
 255         {
 256         default:
 257           abort ();
 258           break;
 259
 260         case ps_done:
 261           /* The pragma was not recognised.  */
 262           break;
 263
 264 #ifdef HANDLE_PRAGMA_PACK
 265         case ps_pack:
 266           if (state == ps_right)
 267             {
 268               maximum_field_alignment = align * 8;
 269               ret_val = 1;
 270             }
 271           else
 272             warning ("malformed `#pragma pack'");
 273           break;
 274 #endif /* HANDLE_PRAGMA_PACK */
 275
 276 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
 277         case ps_push:
 278           if (state == ps_right)
 279             ret_val = push_alignment (align, id);
 280           else
 281             warning ("malformed '#pragma pack(push[,id],<n>)'");
 282           break;
 283
 284         case ps_pop:
 285           if (state == ps_right)
 286             ret_val = pop_alignment (id);
 287           else
 288             warning ("malformed '#pragma pack(pop[,id])'");
 289           break;
 290 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 291
 292 #ifdef HANDLE_PRAGMA_WEAK
 293         case ps_weak:
 294           if (HANDLE_PRAGMA_WEAK)
 295             {
 296               if (state == ps_name)
 297                 ret_val = add_weak (name, NULL);
 298               else if (state == ps_value)
 299                 ret_val = add_weak (name, value);
 300               else
 301                 warning ("malformed `#pragma weak'");
 302             }
 303           else
 304             ret_val = 1; /* Ignore the pragma.  */
 305           break;
 306 #endif /* HANDLE_PRAGMA_WEAK */
 307
 308         case ps_poison:
 309           ret_val = 1;
 310           break;
 311         }
 312
 313       type = state = ps_start;
 314       id = NULL_TREE;
 315
 316       return ret_val;
 317     }
 318
 319   /* If we have been given a token, but it is not an identifier,
 320      or a small constant, then something has gone wrong.  */
 321   if (token)
 322     {
 323       switch (TREE_CODE (token))
 324         {
 325         case IDENTIFIER_NODE:
 326           break;
 327
 328         case INTEGER_CST:
 329           if (TREE_INT_CST_HIGH (token) != 0)
 330             return 0;
 331           break;
 332
 333         default:
 334           return 0;
 335         }
 336     }
 337
 338   switch (state)
 339     {
 340     case ps_start:
 341       type = state = ps_done;
 342 #ifdef HANDLE_PRAGMA_PACK
 343       if (strcmp (string, "pack") == 0)
 344         type = state = ps_pack;
 345 #endif
 346 #ifdef HANDLE_PRAGMA_WEAK
 347       if (strcmp (string, "weak") == 0)
 348         type = state = ps_weak;
 349 #endif
 350       if (strcmp (string, "poison") == 0)
 351         type = state = ps_poison;
 352       break;
 353
 354 #ifdef HANDLE_PRAGMA_WEAK
 355     case ps_weak:
 356       name = permalloc (strlen (string) + 1);
 357       if (name == NULL)
 358         {
 359           warning ("Out of memory parsing #pragma weak");
 360           state = ps_bad;
 361         }
 362       else
 363         {
 364           strcpy (name, string);
 365           state = ps_name;
 366         }
 367       break;
 368
 369     case ps_name:
 370       state = (strcmp (string, "=") ? ps_bad : ps_equals);
 371       break;
 372
 373     case ps_equals:
 374       value = permalloc (strlen (string) + 1);
 375       if (value == NULL)
 376         {
 377           warning ("Out of memory parsing #pragma weak");
 378           state = ps_bad;
 379         }
 380       else
 381         {
 382           strcpy (value, string);
 383           state = ps_value;
 384         }
 385       break;
 386
 387     case ps_value:
 388       state = ps_bad;
 389       break;
 390 #endif /* HANDLE_PRAGMA_WEAK */
 391
 392 #ifdef HANDLE_PRAGMA_PACK
 393     case ps_pack:
 394       state = (strcmp (string, "(") ? ps_bad : ps_left);
 395       break;
 396
 397     case ps_left:
 398
 399       if (token == NULL_TREE)
 400         {
 401           /* #pragma pack () resets packing rules to their
 402              defaults.  */
 403           if (strcmp (string, ")") == 0)
 404             {
 405               align = 0;
 406               state = ps_right;
 407             }
 408           else
 409             state = ps_bad;
 410         }
 411       else if (TREE_CODE (token) == INTEGER_CST)
 412         goto handle_align;
 413
 414 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
 415       else if (TREE_CODE (token) == IDENTIFIER_NODE)
 416         {
 417           if (strcmp (string, "push") == 0)
 418             type = state = ps_push;
 419           else if (strcmp (string, "pop") == 0)
 420             type = state = ps_pop;
 421           else
 422             state = ps_bad;
 423         }
 424 #endif
 425       else
 426         state = ps_bad;
 427       break;
 428
 429     handle_align:
 430       align = TREE_INT_CST_LOW (token);
 431       switch (align)
 432         {
 433         case 1:
 434         case 2:
 435         case 4:
 436         case 8:
 437         case 16:
 438           state = ps_align;
 439           break;
 440
 441         default:
 442           state = ps_bad;
 443           break;
 444         }
 445       break;
 446
 447     case ps_align:
 448       state = (strcmp (string, ")") ? ps_bad : ps_right);
 449       break;
 450
 451     case ps_right:
 452       state = ps_bad;
 453       break;
 454 #endif /* HANDLE_PRAGMA_PACK */
 455
 456 #ifdef HANDLE_PRAGMA_PACK_PUSH_POP
 457     case ps_push:
 458       state = (strcmp (string, ",") ? ps_bad : ps_pushcomma);
 459       break;
 460
 461     case ps_pushid:
 462       state = (strcmp (string, ",") ? ps_bad : ps_pushcomma2);
 463       break;
 464
 465     case ps_pushcomma:
 466       if (token && TREE_CODE (token) == IDENTIFIER_NODE)
 467         {
 468           id = token;
 469           state = ps_pushid;
 470           break;
 471         }
 472
 473       /* else fall through */
 474     case ps_pushcomma2:
 475       if (token && TREE_CODE (token) == INTEGER_CST)
 476         goto handle_align;
 477       else
 478         state = ps_bad;
 479       break;
 480
 481     case ps_pop:
 482       if (strcmp (string, ",") == 0)
 483         state = ps_popcomma;
 484       else
 485         state = (strcmp (string, ")") ? ps_bad : ps_right);
 486       break;
 487
 488     case ps_popcomma:
 489       if (token && TREE_CODE (token) == IDENTIFIER_NODE)
 490         {
 491           id = token;
 492           state = ps_align;
 493         }
 494       else
 495         state = ps_bad;
 496       break;
 497 #endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
 498
 499     case ps_poison:
 500       if (token && TREE_CODE (token) != IDENTIFIER_NODE)
 501         state = ps_bad;
 502       break;
 503
 504     case ps_bad:
 505     case ps_done:
 506       break;
 507
 508     default:
 509       abort ();
 510     }
 511
 512   return 1;
 513 }
 514 #endif /* HANDLE_GENERIC_PRAGMAS */