gcc/attribs.c

   1 /* Functions dealing with attribute handling, used by most front ends.
   2    Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
   3    2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
   4    Free Software Foundation, Inc.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "tree.h"
  27 #include "flags.h"
  28 #include "diagnostic-core.h"
  29 #include "ggc.h"
  30 #include "tm_p.h"
  31 #include "cpplib.h"
  32 #include "target.h"
  33 #include "langhooks.h"
  34 #include "hashtab.h"
  35 #include "plugin.h"
  36
  37 static void init_attributes (void);
  38
  39 /* Table of the tables of attributes (common, language, format, machine)
  40    searched.  */
  41 static const struct attribute_spec *attribute_tables[4];
  42
  43 /* Hashtable mapping names (represented as substrings) to attribute specs. */
  44 static htab_t attribute_hash;
  45
  46 /* Substring representation.  */
  47
  48 struct substring
  49 {
  50   const char *str;
  51   int length;
  52 };
  53
  54 static bool attributes_initialized = false;
  55
  56 /* Default empty table of attributes.  */
  57
  58 static const struct attribute_spec empty_attribute_table[] =
  59 {
  60   { NULL, 0, 0, false, false, false, NULL }
  61 };
  62
  63 /* Return base name of the attribute.  Ie '__attr__' is turned into 'attr'.
  64    To avoid need for copying, we simply return length of the string.  */
  65
  66 static void
  67 extract_attribute_substring (struct substring *str)
  68 {
  69   if (str->length > 4 && str->str[0] == '_' && str->str[1] == '_'
  70       && str->str[str->length - 1] == '_' && str->str[str->length - 2] == '_')
  71     {
  72       str->length -= 4;
  73       str->str += 2;
  74     }
  75 }
  76
  77 /* Simple hash function to avoid need to scan whole string.  */
  78
  79 static inline hashval_t
  80 substring_hash (const char *str, int l)
  81 {
  82   return str[0] + str[l - 1] * 256 + l * 65536;
  83 }
  84
  85 /* Used for attribute_hash.  */
  86
  87 static hashval_t
  88 hash_attr (const void *p)
  89 {
  90   const struct attribute_spec *const spec = (const struct attribute_spec *) p;
  91   const int l = strlen (spec->name);
  92
  93   return substring_hash (spec->name, l);
  94 }
  95
  96 /* Used for attribute_hash.  */
  97
  98 static int
  99 eq_attr (const void *p, const void *q)
 100 {
 101   const struct attribute_spec *const spec = (const struct attribute_spec *) p;
 102   const struct substring *const str = (const struct substring *) q;
 103
 104   return (!strncmp (spec->name, str->str, str->length) && !spec->name[str->length]);
 105 }
 106
 107 /* Initialize attribute tables, and make some sanity checks
 108    if --enable-checking.  */
 109
 110 static void
 111 init_attributes (void)
 112 {
 113   size_t i;
 114   int k;
 115
 116   attribute_tables[0] = lang_hooks.common_attribute_table;
 117   attribute_tables[1] = lang_hooks.attribute_table;
 118   attribute_tables[2] = lang_hooks.format_attribute_table;
 119   attribute_tables[3] = targetm.attribute_table;
 120
 121   /* Translate NULL pointers to pointers to the empty table.  */
 122   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 123     if (attribute_tables[i] == NULL)
 124       attribute_tables[i] = empty_attribute_table;
 125
 126 #ifdef ENABLE_CHECKING
 127   /* Make some sanity checks on the attribute tables.  */
 128   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 129     {
 130       int j;
 131
 132       for (j = 0; attribute_tables[i][j].name != NULL; j++)
 133         {
 134           /* The name must not begin and end with __.  */
 135           const char *name = attribute_tables[i][j].name;
 136           int len = strlen (name);
 137
 138           gcc_assert (!(name[0] == '_' && name[1] == '_'
 139                         && name[len - 1] == '_' && name[len - 2] == '_'));
 140
 141           /* The minimum and maximum lengths must be consistent.  */
 142           gcc_assert (attribute_tables[i][j].min_length >= 0);
 143
 144           gcc_assert (attribute_tables[i][j].max_length == -1
 145                       || (attribute_tables[i][j].max_length
 146                           >= attribute_tables[i][j].min_length));
 147
 148           /* An attribute cannot require both a DECL and a TYPE.  */
 149           gcc_assert (!attribute_tables[i][j].decl_required
 150                       || !attribute_tables[i][j].type_required);
 151
 152           /* If an attribute requires a function type, in particular
 153              it requires a type.  */
 154           gcc_assert (!attribute_tables[i][j].function_type_required
 155                       || attribute_tables[i][j].type_required);
 156         }
 157     }
 158
 159   /* Check that each name occurs just once in each table.  */
 160   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 161     {
 162       int j, k;
 163       for (j = 0; attribute_tables[i][j].name != NULL; j++)
 164         for (k = j + 1; attribute_tables[i][k].name != NULL; k++)
 165           gcc_assert (strcmp (attribute_tables[i][j].name,
 166                               attribute_tables[i][k].name));
 167     }
 168   /* Check that no name occurs in more than one table.  */
 169   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 170     {
 171       size_t j, k, l;
 172
 173       for (j = i + 1; j < ARRAY_SIZE (attribute_tables); j++)
 174         for (k = 0; attribute_tables[i][k].name != NULL; k++)
 175           for (l = 0; attribute_tables[j][l].name != NULL; l++)
 176             gcc_assert (strcmp (attribute_tables[i][k].name,
 177                                 attribute_tables[j][l].name));
 178     }
 179 #endif
 180
 181   attribute_hash = htab_create (200, hash_attr, eq_attr, NULL);
 182   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 183     for (k = 0; attribute_tables[i][k].name != NULL; k++)
 184       {
 185         register_attribute (&attribute_tables[i][k]);
 186       }
 187   invoke_plugin_callbacks (PLUGIN_ATTRIBUTES, NULL);
 188   attributes_initialized = true;
 189 }
 190
 191 /* Insert a single ATTR into the attribute table.  */
 192
 193 void
 194 register_attribute (const struct attribute_spec *attr)
 195 {
 196   struct substring str;
 197   void **slot;
 198
 199   str.str = attr->name;
 200   str.length = strlen (str.str);
 201   slot = htab_find_slot_with_hash (attribute_hash, &str,
 202                                    substring_hash (str.str, str.length),
 203                                    INSERT);
 204   gcc_assert (!*slot);
 205   *slot = (void *) CONST_CAST (struct attribute_spec *, attr);
 206 }
 207
 208 /* Return the spec for the attribute named NAME.  */
 209
 210 const struct attribute_spec *
 211 lookup_attribute_spec (tree name)
 212 {
 213   struct substring attr;
 214
 215   attr.str = IDENTIFIER_POINTER (name);
 216   attr.length = IDENTIFIER_LENGTH (name);
 217   extract_attribute_substring (&attr);
 218   return (const struct attribute_spec *)
 219     htab_find_with_hash (attribute_hash, &attr,
 220                          substring_hash (attr.str, attr.length));
 221 }
 222 \f
 223 /* Process the attributes listed in ATTRIBUTES and install them in *NODE,
 224    which is either a DECL (including a TYPE_DECL) or a TYPE.  If a DECL,
 225    it should be modified in place; if a TYPE, a copy should be created
 226    unless ATTR_FLAG_TYPE_IN_PLACE is set in FLAGS.  FLAGS gives further
 227    information, in the form of a bitwise OR of flags in enum attribute_flags
 228    from tree.h.  Depending on these flags, some attributes may be
 229    returned to be applied at a later stage (for example, to apply
 230    a decl attribute to the declaration rather than to its type).  */
 231
 232 tree
 233 decl_attributes (tree *node, tree attributes, int flags)
 234 {
 235   tree a;
 236   tree returned_attrs = NULL_TREE;
 237
 238   if (TREE_TYPE (*node) == error_mark_node)
 239     return NULL_TREE;
 240
 241   if (!attributes_initialized)
 242     init_attributes ();
 243
 244   /* If this is a function and the user used #pragma GCC optimize, add the
 245      options to the attribute((optimize(...))) list.  */
 246   if (TREE_CODE (*node) == FUNCTION_DECL && current_optimize_pragma)
 247     {
 248       tree cur_attr = lookup_attribute ("optimize", attributes);
 249       tree opts = copy_list (current_optimize_pragma);
 250
 251       if (! cur_attr)
 252         attributes
 253           = tree_cons (get_identifier ("optimize"), opts, attributes);
 254       else
 255         TREE_VALUE (cur_attr) = chainon (opts, TREE_VALUE (cur_attr));
 256     }
 257
 258   if (TREE_CODE (*node) == FUNCTION_DECL
 259       && optimization_current_node != optimization_default_node
 260       && !DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node))
 261     DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node) = optimization_current_node;
 262
 263   /* If this is a function and the user used #pragma GCC target, add the
 264      options to the attribute((target(...))) list.  */
 265   if (TREE_CODE (*node) == FUNCTION_DECL
 266       && current_target_pragma
 267       && targetm.target_option.valid_attribute_p (*node, NULL_TREE,
 268                                                   current_target_pragma, 0))
 269     {
 270       tree cur_attr = lookup_attribute ("target", attributes);
 271       tree opts = copy_list (current_target_pragma);
 272
 273       if (! cur_attr)
 274         attributes = tree_cons (get_identifier ("target"), opts, attributes);
 275       else
 276         TREE_VALUE (cur_attr) = chainon (opts, TREE_VALUE (cur_attr));
 277     }
 278
 279   targetm.insert_attributes (*node, &attributes);
 280
 281   for (a = attributes; a; a = TREE_CHAIN (a))
 282     {
 283       tree name = TREE_PURPOSE (a);
 284       tree args = TREE_VALUE (a);
 285       tree *anode = node;
 286       const struct attribute_spec *spec = lookup_attribute_spec (name);
 287       bool no_add_attrs = 0;
 288       int fn_ptr_quals = 0;
 289       tree fn_ptr_tmp = NULL_TREE;
 290
 291       if (spec == NULL)
 292         {
 293           warning (OPT_Wattributes, "%qE attribute directive ignored",
 294                    name);
 295           continue;
 296         }
 297       else if (list_length (args) < spec->min_length
 298                || (spec->max_length >= 0
 299                    && list_length (args) > spec->max_length))
 300         {
 301           error ("wrong number of arguments specified for %qE attribute",
 302                  name);
 303           continue;
 304         }
 305       gcc_assert (is_attribute_p (spec->name, name));
 306
 307       if (spec->decl_required && !DECL_P (*anode))
 308         {
 309           if (flags & ((int) ATTR_FLAG_DECL_NEXT
 310                        | (int) ATTR_FLAG_FUNCTION_NEXT
 311                        | (int) ATTR_FLAG_ARRAY_NEXT))
 312             {
 313               /* Pass on this attribute to be tried again.  */
 314               returned_attrs = tree_cons (name, args, returned_attrs);
 315               continue;
 316             }
 317           else
 318             {
 319               warning (OPT_Wattributes, "%qE attribute does not apply to types",
 320                        name);
 321               continue;
 322             }
 323         }
 324
 325       /* If we require a type, but were passed a decl, set up to make a
 326          new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
 327          would have applied if we'd been passed a type, but we cannot modify
 328          the decl's type in place here.  */
 329       if (spec->type_required && DECL_P (*anode))
 330         {
 331           anode = &TREE_TYPE (*anode);
 332           /* Allow ATTR_FLAG_TYPE_IN_PLACE for the type's naming decl.  */
 333           if (!(TREE_CODE (*anode) == TYPE_DECL
 334                 && *anode == TYPE_NAME (TYPE_MAIN_VARIANT
 335                                         (TREE_TYPE (*anode)))))
 336             flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 337         }
 338
 339       if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
 340           && TREE_CODE (*anode) != METHOD_TYPE)
 341         {
 342           if (TREE_CODE (*anode) == POINTER_TYPE
 343               && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
 344                   || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
 345             {
 346               /* OK, this is a bit convoluted.  We can't just make a copy
 347                  of the pointer type and modify its TREE_TYPE, because if
 348                  we change the attributes of the target type the pointer
 349                  type needs to have a different TYPE_MAIN_VARIANT.  So we
 350                  pull out the target type now, frob it as appropriate, and
 351                  rebuild the pointer type later.
 352
 353                  This would all be simpler if attributes were part of the
 354                  declarator, grumble grumble.  */
 355               fn_ptr_tmp = TREE_TYPE (*anode);
 356               fn_ptr_quals = TYPE_QUALS (*anode);
 357               anode = &fn_ptr_tmp;
 358               flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 359             }
 360           else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
 361             {
 362               /* Pass on this attribute to be tried again.  */
 363               returned_attrs = tree_cons (name, args, returned_attrs);
 364               continue;
 365             }
 366
 367           if (TREE_CODE (*anode) != FUNCTION_TYPE
 368               && TREE_CODE (*anode) != METHOD_TYPE)
 369             {
 370               warning (OPT_Wattributes,
 371                        "%qE attribute only applies to function types",
 372                        name);
 373               continue;
 374             }
 375         }
 376
 377       if (TYPE_P (*anode)
 378           && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 379           && TYPE_SIZE (*anode) != NULL_TREE)
 380         {
 381           warning (OPT_Wattributes, "type attributes ignored after type is already defined");
 382           continue;
 383         }
 384
 385       if (spec->handler != NULL)
 386         returned_attrs = chainon ((*spec->handler) (anode, name, args,
 387                                                     flags, &no_add_attrs),
 388                                   returned_attrs);
 389
 390       /* Layout the decl in case anything changed.  */
 391       if (spec->type_required && DECL_P (*node)
 392           && (TREE_CODE (*node) == VAR_DECL
 393               || TREE_CODE (*node) == PARM_DECL
 394               || TREE_CODE (*node) == RESULT_DECL))
 395         relayout_decl (*node);
 396
 397       if (!no_add_attrs)
 398         {
 399           tree old_attrs;
 400           tree a;
 401
 402           if (DECL_P (*anode))
 403             old_attrs = DECL_ATTRIBUTES (*anode);
 404           else
 405             old_attrs = TYPE_ATTRIBUTES (*anode);
 406
 407           for (a = lookup_attribute (spec->name, old_attrs);
 408                a != NULL_TREE;
 409                a = lookup_attribute (spec->name, TREE_CHAIN (a)))
 410             {
 411               if (simple_cst_equal (TREE_VALUE (a), args) == 1)
 412                 break;
 413             }
 414
 415           if (a == NULL_TREE)
 416             {
 417               /* This attribute isn't already in the list.  */
 418               if (DECL_P (*anode))
 419                 DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 420               else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 421                 {
 422                   TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 423                   /* If this is the main variant, also push the attributes
 424                      out to the other variants.  */
 425                   if (*anode == TYPE_MAIN_VARIANT (*anode))
 426                     {
 427                       tree variant;
 428                       for (variant = *anode; variant;
 429                            variant = TYPE_NEXT_VARIANT (variant))
 430                         {
 431                           if (TYPE_ATTRIBUTES (variant) == old_attrs)
 432                             TYPE_ATTRIBUTES (variant)
 433                               = TYPE_ATTRIBUTES (*anode);
 434                           else if (!lookup_attribute
 435                                    (spec->name, TYPE_ATTRIBUTES (variant)))
 436                             TYPE_ATTRIBUTES (variant) = tree_cons
 437                               (name, args, TYPE_ATTRIBUTES (variant));
 438                         }
 439                     }
 440                 }
 441               else
 442                 *anode = build_type_attribute_variant (*anode,
 443                                                        tree_cons (name, args,
 444                                                                   old_attrs));
 445             }
 446         }
 447
 448       if (fn_ptr_tmp)
 449         {
 450           /* Rebuild the function pointer type and put it in the
 451              appropriate place.  */
 452           fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
 453           if (fn_ptr_quals)
 454             fn_ptr_tmp = build_qualified_type (fn_ptr_tmp, fn_ptr_quals);
 455           if (DECL_P (*node))
 456             TREE_TYPE (*node) = fn_ptr_tmp;
 457           else
 458             {
 459               gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
 460               *node = fn_ptr_tmp;
 461             }
 462         }
 463     }
 464
 465   return returned_attrs;
 466 }