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           /* Allow ATTR_FLAG_TYPE_IN_PLACE for the type's naming decl.  */
 284           if (!(TREE_CODE (*anode) == TYPE_DECL
 285                 && *anode == TYPE_NAME (TYPE_MAIN_VARIANT
 286                                         (TREE_TYPE (*anode)))))
 287             flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 288         }
 289
 290       if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
 291           && TREE_CODE (*anode) != METHOD_TYPE)
 292         {
 293           if (TREE_CODE (*anode) == POINTER_TYPE
 294               && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
 295                   || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
 296             {
 297               /* OK, this is a bit convoluted.  We can't just make a copy
 298                  of the pointer type and modify its TREE_TYPE, because if
 299                  we change the attributes of the target type the pointer
 300                  type needs to have a different TYPE_MAIN_VARIANT.  So we
 301                  pull out the target type now, frob it as appropriate, and
 302                  rebuild the pointer type later.
 303
 304                  This would all be simpler if attributes were part of the
 305                  declarator, grumble grumble.  */
 306               fn_ptr_tmp = TREE_TYPE (*anode);
 307               anode = &fn_ptr_tmp;
 308               flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 309             }
 310           else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
 311             {
 312               /* Pass on this attribute to be tried again.  */
 313               returned_attrs = tree_cons (name, args, returned_attrs);
 314               continue;
 315             }
 316
 317           if (TREE_CODE (*anode) != FUNCTION_TYPE
 318               && TREE_CODE (*anode) != METHOD_TYPE)
 319             {
 320               warning (OPT_Wattributes,
 321                        "%qs attribute only applies to function types",
 322                        IDENTIFIER_POINTER (name));
 323               continue;
 324             }
 325         }
 326
 327       if (TYPE_P (*anode)
 328           && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 329           && TYPE_SIZE (*anode) != NULL_TREE)
 330         {
 331           warning (OPT_Wattributes, "type attributes ignored after type is already defined");
 332           continue;
 333         }
 334
 335       if (spec->handler != NULL)
 336         returned_attrs = chainon ((*spec->handler) (anode, name, args,
 337                                                     flags, &no_add_attrs),
 338                                   returned_attrs);
 339
 340       /* Layout the decl in case anything changed.  */
 341       if (spec->type_required && DECL_P (*node)
 342           && (TREE_CODE (*node) == VAR_DECL
 343               || TREE_CODE (*node) == PARM_DECL
 344               || TREE_CODE (*node) == RESULT_DECL))
 345         relayout_decl (*node);
 346
 347       if (!no_add_attrs)
 348         {
 349           tree old_attrs;
 350           tree a;
 351
 352           if (DECL_P (*anode))
 353             old_attrs = DECL_ATTRIBUTES (*anode);
 354           else
 355             old_attrs = TYPE_ATTRIBUTES (*anode);
 356
 357           for (a = lookup_attribute (spec->name, old_attrs);
 358                a != NULL_TREE;
 359                a = lookup_attribute (spec->name, TREE_CHAIN (a)))
 360             {
 361               if (simple_cst_equal (TREE_VALUE (a), args) == 1)
 362                 break;
 363             }
 364
 365           if (a == NULL_TREE)
 366             {
 367               /* This attribute isn't already in the list.  */
 368               if (DECL_P (*anode))
 369                 DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 370               else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 371                 {
 372                   TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 373                   /* If this is the main variant, also push the attributes
 374                      out to the other variants.  */
 375                   if (*anode == TYPE_MAIN_VARIANT (*anode))
 376                     {
 377                       tree variant;
 378                       for (variant = *anode; variant;
 379                            variant = TYPE_NEXT_VARIANT (variant))
 380                         {
 381                           if (TYPE_ATTRIBUTES (variant) == old_attrs)
 382                             TYPE_ATTRIBUTES (variant)
 383                               = TYPE_ATTRIBUTES (*anode);
 384                           else if (!lookup_attribute
 385                                    (spec->name, TYPE_ATTRIBUTES (variant)))
 386                             TYPE_ATTRIBUTES (variant) = tree_cons
 387                               (name, args, TYPE_ATTRIBUTES (variant));
 388                         }
 389                     }
 390                 }
 391               else
 392                 *anode = build_type_attribute_variant (*anode,
 393                                                        tree_cons (name, args,
 394                                                                   old_attrs));
 395             }
 396         }
 397
 398       if (fn_ptr_tmp)
 399         {
 400           /* Rebuild the function pointer type and put it in the
 401              appropriate place.  */
 402           fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
 403           if (DECL_P (*node))
 404             TREE_TYPE (*node) = fn_ptr_tmp;
 405           else
 406             {
 407               gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
 408               *node = fn_ptr_tmp;
 409             }
 410         }
 411     }
 412
 413   return returned_attrs;
 414 }