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