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 (!attributes_initialized)
 229     init_attributes ();
 230
 231   targetm.insert_attributes (*node, &attributes);
 232
 233   for (a = attributes; a; a = TREE_CHAIN (a))
 234     {
 235       tree name = TREE_PURPOSE (a);
 236       tree args = TREE_VALUE (a);
 237       tree *anode = node;
 238       const struct attribute_spec *spec = lookup_attribute_spec (name);
 239       bool no_add_attrs = 0;
 240       tree fn_ptr_tmp = NULL_TREE;
 241
 242       if (spec == NULL)
 243         {
 244           warning (OPT_Wattributes, "%qs attribute directive ignored",
 245                    IDENTIFIER_POINTER (name));
 246           continue;
 247         }
 248       else if (list_length (args) < spec->min_length
 249                || (spec->max_length >= 0
 250                    && list_length (args) > spec->max_length))
 251         {
 252           error ("wrong number of arguments specified for %qs attribute",
 253                  IDENTIFIER_POINTER (name));
 254           continue;
 255         }
 256       gcc_assert (is_attribute_p (spec->name, name));
 257
 258       if (spec->decl_required && !DECL_P (*anode))
 259         {
 260           if (flags & ((int) ATTR_FLAG_DECL_NEXT
 261                        | (int) ATTR_FLAG_FUNCTION_NEXT
 262                        | (int) ATTR_FLAG_ARRAY_NEXT))
 263             {
 264               /* Pass on this attribute to be tried again.  */
 265               returned_attrs = tree_cons (name, args, returned_attrs);
 266               continue;
 267             }
 268           else
 269             {
 270               warning (OPT_Wattributes, "%qs attribute does not apply to types",
 271                        IDENTIFIER_POINTER (name));
 272               continue;
 273             }
 274         }
 275
 276       /* If we require a type, but were passed a decl, set up to make a
 277          new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
 278          would have applied if we'd been passed a type, but we cannot modify
 279          the decl's type in place here.  */
 280       if (spec->type_required && DECL_P (*anode))
 281         {
 282           anode = &TREE_TYPE (*anode);
 283           flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 284         }
 285
 286       if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
 287           && TREE_CODE (*anode) != METHOD_TYPE)
 288         {
 289           if (TREE_CODE (*anode) == POINTER_TYPE
 290               && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
 291                   || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
 292             {
 293               /* OK, this is a bit convoluted.  We can't just make a copy
 294                  of the pointer type and modify its TREE_TYPE, because if
 295                  we change the attributes of the target type the pointer
 296                  type needs to have a different TYPE_MAIN_VARIANT.  So we
 297                  pull out the target type now, frob it as appropriate, and
 298                  rebuild the pointer type later.
 299
 300                  This would all be simpler if attributes were part of the
 301                  declarator, grumble grumble.  */
 302               fn_ptr_tmp = TREE_TYPE (*anode);
 303               anode = &fn_ptr_tmp;
 304               flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 305             }
 306           else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
 307             {
 308               /* Pass on this attribute to be tried again.  */
 309               returned_attrs = tree_cons (name, args, returned_attrs);
 310               continue;
 311             }
 312
 313           if (TREE_CODE (*anode) != FUNCTION_TYPE
 314               && TREE_CODE (*anode) != METHOD_TYPE)
 315             {
 316               warning (OPT_Wattributes,
 317                        "%qs attribute only applies to function types",
 318                        IDENTIFIER_POINTER (name));
 319               continue;
 320             }
 321         }
 322
 323       if (TYPE_P (*anode)
 324           && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 325           && TYPE_SIZE (*anode) != NULL_TREE)
 326         {
 327           warning (OPT_Wattributes, "type attributes ignored after type is already defined");
 328           continue;
 329         }
 330
 331       if (spec->handler != NULL)
 332         returned_attrs = chainon ((*spec->handler) (anode, name, args,
 333                                                     flags, &no_add_attrs),
 334                                   returned_attrs);
 335
 336       /* Layout the decl in case anything changed.  */
 337       if (spec->type_required && DECL_P (*node)
 338           && (TREE_CODE (*node) == VAR_DECL
 339               || TREE_CODE (*node) == PARM_DECL
 340               || TREE_CODE (*node) == RESULT_DECL))
 341         relayout_decl (*node);
 342
 343       if (!no_add_attrs)
 344         {
 345           tree old_attrs;
 346           tree a;
 347
 348           if (DECL_P (*anode))
 349             old_attrs = DECL_ATTRIBUTES (*anode);
 350           else
 351             old_attrs = TYPE_ATTRIBUTES (*anode);
 352
 353           for (a = lookup_attribute (spec->name, old_attrs);
 354                a != NULL_TREE;
 355                a = lookup_attribute (spec->name, TREE_CHAIN (a)))
 356             {
 357               if (simple_cst_equal (TREE_VALUE (a), args) == 1)
 358                 break;
 359             }
 360
 361           if (a == NULL_TREE)
 362             {
 363               /* This attribute isn't already in the list.  */
 364               if (DECL_P (*anode))
 365                 DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 366               else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 367                 {
 368                   TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 369                   /* If this is the main variant, also push the attributes
 370                      out to the other variants.  */
 371                   if (*anode == TYPE_MAIN_VARIANT (*anode))
 372                     {
 373                       tree variant;
 374                       for (variant = *anode; variant;
 375                            variant = TYPE_NEXT_VARIANT (variant))
 376                         {
 377                           if (TYPE_ATTRIBUTES (variant) == old_attrs)
 378                             TYPE_ATTRIBUTES (variant)
 379                               = TYPE_ATTRIBUTES (*anode);
 380                           else if (!lookup_attribute
 381                                    (spec->name, TYPE_ATTRIBUTES (variant)))
 382                             TYPE_ATTRIBUTES (variant) = tree_cons
 383                               (name, args, TYPE_ATTRIBUTES (variant));
 384                         }
 385                     }
 386                 }
 387               else
 388                 *anode = build_type_attribute_variant (*anode,
 389                                                        tree_cons (name, args,
 390                                                                   old_attrs));
 391             }
 392         }
 393
 394       if (fn_ptr_tmp)
 395         {
 396           /* Rebuild the function pointer type and put it in the
 397              appropriate place.  */
 398           fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
 399           if (DECL_P (*node))
 400             TREE_TYPE (*node) = fn_ptr_tmp;
 401           else
 402             {
 403               gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
 404               *node = fn_ptr_tmp;
 405             }
 406         }
 407     }
 408
 409   return returned_attrs;
 410 }