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 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 3, 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 COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tm.h"
  25 #include "tree.h"
  26 #include "flags.h"
  27 #include "toplev.h"
  28 #include "output.h"
  29 #include "rtl.h"
  30 #include "ggc.h"
  31 #include "tm_p.h"
  32 #include "cpplib.h"
  33 #include "target.h"
  34 #include "langhooks.h"
  35 #include "hashtab.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         struct substring str;
 186         const void **slot;
 187
 188         str.str = attribute_tables[i][k].name;
 189         str.length = strlen (attribute_tables[i][k].name);
 190         slot = (const void **)htab_find_slot_with_hash (attribute_hash, &str,
 191                                          substring_hash (str.str, str.length),
 192                                          INSERT);
 193         gcc_assert (!*slot);
 194         *slot = &attribute_tables[i][k];
 195       }
 196   attributes_initialized = true;
 197 }
 198
 199 /* Return the spec for the attribute named NAME.  */
 200
 201 const struct attribute_spec *
 202 lookup_attribute_spec (tree name)
 203 {
 204   struct substring attr;
 205
 206   attr.str = IDENTIFIER_POINTER (name);
 207   attr.length = IDENTIFIER_LENGTH (name);
 208   extract_attribute_substring (&attr);
 209   return htab_find_with_hash (attribute_hash, &attr,
 210                               substring_hash (attr.str, attr.length));
 211 }
 212 \f
 213 /* Process the attributes listed in ATTRIBUTES and install them in *NODE,
 214    which is either a DECL (including a TYPE_DECL) or a TYPE.  If a DECL,
 215    it should be modified in place; if a TYPE, a copy should be created
 216    unless ATTR_FLAG_TYPE_IN_PLACE is set in FLAGS.  FLAGS gives further
 217    information, in the form of a bitwise OR of flags in enum attribute_flags
 218    from tree.h.  Depending on these flags, some attributes may be
 219    returned to be applied at a later stage (for example, to apply
 220    a decl attribute to the declaration rather than to its type).  */
 221
 222 tree
 223 decl_attributes (tree *node, tree attributes, int flags)
 224 {
 225   tree a;
 226   tree returned_attrs = NULL_TREE;
 227
 228   if (TREE_TYPE (*node) == error_mark_node)
 229     return NULL_TREE;
 230
 231   if (!attributes_initialized)
 232     init_attributes ();
 233
 234   targetm.insert_attributes (*node, &attributes);
 235
 236   for (a = attributes; a; a = TREE_CHAIN (a))
 237     {
 238       tree name = TREE_PURPOSE (a);
 239       tree args = TREE_VALUE (a);
 240       tree *anode = node;
 241       const struct attribute_spec *spec = lookup_attribute_spec (name);
 242       bool no_add_attrs = 0;
 243       tree fn_ptr_tmp = NULL_TREE;
 244
 245       if (spec == NULL)
 246         {
 247           warning (OPT_Wattributes, "%qs attribute directive ignored",
 248                    IDENTIFIER_POINTER (name));
 249           continue;
 250         }
 251       else if (list_length (args) < spec->min_length
 252                || (spec->max_length >= 0
 253                    && list_length (args) > spec->max_length))
 254         {
 255           error ("wrong number of arguments specified for %qs attribute",
 256                  IDENTIFIER_POINTER (name));
 257           continue;
 258         }
 259       gcc_assert (is_attribute_p (spec->name, name));
 260
 261       if (spec->decl_required && !DECL_P (*anode))
 262         {
 263           if (flags & ((int) ATTR_FLAG_DECL_NEXT
 264                        | (int) ATTR_FLAG_FUNCTION_NEXT
 265                        | (int) ATTR_FLAG_ARRAY_NEXT))
 266             {
 267               /* Pass on this attribute to be tried again.  */
 268               returned_attrs = tree_cons (name, args, returned_attrs);
 269               continue;
 270             }
 271           else
 272             {
 273               warning (OPT_Wattributes, "%qs attribute does not apply to types",
 274                        IDENTIFIER_POINTER (name));
 275               continue;
 276             }
 277         }
 278
 279       /* If we require a type, but were passed a decl, set up to make a
 280          new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
 281          would have applied if we'd been passed a type, but we cannot modify
 282          the decl's type in place here.  */
 283       if (spec->type_required && DECL_P (*anode))
 284         {
 285           anode = &TREE_TYPE (*anode);
 286           /* Allow ATTR_FLAG_TYPE_IN_PLACE for the type's naming decl.  */
 287           if (!(TREE_CODE (*anode) == TYPE_DECL
 288                 && *anode == TYPE_NAME (TYPE_MAIN_VARIANT
 289                                         (TREE_TYPE (*anode)))))
 290             flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 291         }
 292
 293       if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
 294           && TREE_CODE (*anode) != METHOD_TYPE)
 295         {
 296           if (TREE_CODE (*anode) == POINTER_TYPE
 297               && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
 298                   || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
 299             {
 300               /* OK, this is a bit convoluted.  We can't just make a copy
 301                  of the pointer type and modify its TREE_TYPE, because if
 302                  we change the attributes of the target type the pointer
 303                  type needs to have a different TYPE_MAIN_VARIANT.  So we
 304                  pull out the target type now, frob it as appropriate, and
 305                  rebuild the pointer type later.
 306
 307                  This would all be simpler if attributes were part of the
 308                  declarator, grumble grumble.  */
 309               fn_ptr_tmp = TREE_TYPE (*anode);
 310               anode = &fn_ptr_tmp;
 311               flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 312             }
 313           else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
 314             {
 315               /* Pass on this attribute to be tried again.  */
 316               returned_attrs = tree_cons (name, args, returned_attrs);
 317               continue;
 318             }
 319
 320           if (TREE_CODE (*anode) != FUNCTION_TYPE
 321               && TREE_CODE (*anode) != METHOD_TYPE)
 322             {
 323               warning (OPT_Wattributes,
 324                        "%qs attribute only applies to function types",
 325                        IDENTIFIER_POINTER (name));
 326               continue;
 327             }
 328         }
 329
 330       if (TYPE_P (*anode)
 331           && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 332           && TYPE_SIZE (*anode) != NULL_TREE)
 333         {
 334           warning (OPT_Wattributes, "type attributes ignored after type is already defined");
 335           continue;
 336         }
 337
 338       if (spec->handler != NULL)
 339         returned_attrs = chainon ((*spec->handler) (anode, name, args,
 340                                                     flags, &no_add_attrs),
 341                                   returned_attrs);
 342
 343       /* Layout the decl in case anything changed.  */
 344       if (spec->type_required && DECL_P (*node)
 345           && (TREE_CODE (*node) == VAR_DECL
 346               || TREE_CODE (*node) == PARM_DECL
 347               || TREE_CODE (*node) == RESULT_DECL))
 348         relayout_decl (*node);
 349
 350       if (!no_add_attrs)
 351         {
 352           tree old_attrs;
 353           tree a;
 354
 355           if (DECL_P (*anode))
 356             old_attrs = DECL_ATTRIBUTES (*anode);
 357           else
 358             old_attrs = TYPE_ATTRIBUTES (*anode);
 359
 360           for (a = lookup_attribute (spec->name, old_attrs);
 361                a != NULL_TREE;
 362                a = lookup_attribute (spec->name, TREE_CHAIN (a)))
 363             {
 364               if (simple_cst_equal (TREE_VALUE (a), args) == 1)
 365                 break;
 366             }
 367
 368           if (a == NULL_TREE)
 369             {
 370               /* This attribute isn't already in the list.  */
 371               if (DECL_P (*anode))
 372                 DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 373               else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 374                 {
 375                   TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 376                   /* If this is the main variant, also push the attributes
 377                      out to the other variants.  */
 378                   if (*anode == TYPE_MAIN_VARIANT (*anode))
 379                     {
 380                       tree variant;
 381                       for (variant = *anode; variant;
 382                            variant = TYPE_NEXT_VARIANT (variant))
 383                         {
 384                           if (TYPE_ATTRIBUTES (variant) == old_attrs)
 385                             TYPE_ATTRIBUTES (variant)
 386                               = TYPE_ATTRIBUTES (*anode);
 387                           else if (!lookup_attribute
 388                                    (spec->name, TYPE_ATTRIBUTES (variant)))
 389                             TYPE_ATTRIBUTES (variant) = tree_cons
 390                               (name, args, TYPE_ATTRIBUTES (variant));
 391                         }
 392                     }
 393                 }
 394               else
 395                 *anode = build_type_attribute_variant (*anode,
 396                                                        tree_cons (name, args,
 397                                                                   old_attrs));
 398             }
 399         }
 400
 401       if (fn_ptr_tmp)
 402         {
 403           /* Rebuild the function pointer type and put it in the
 404              appropriate place.  */
 405           fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
 406           if (DECL_P (*node))
 407             TREE_TYPE (*node) = fn_ptr_tmp;
 408           else
 409             {
 410               gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
 411               *node = fn_ptr_tmp;
 412             }
 413         }
 414     }
 415
 416   return returned_attrs;
 417 }