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 (const struct attribute_spec *)
 210     htab_find_with_hash (attribute_hash, &attr,
 211                          substring_hash (attr.str, attr.length));
 212 }
 213 \f
 214 /* Process the attributes listed in ATTRIBUTES and install them in *NODE,
 215    which is either a DECL (including a TYPE_DECL) or a TYPE.  If a DECL,
 216    it should be modified in place; if a TYPE, a copy should be created
 217    unless ATTR_FLAG_TYPE_IN_PLACE is set in FLAGS.  FLAGS gives further
 218    information, in the form of a bitwise OR of flags in enum attribute_flags
 219    from tree.h.  Depending on these flags, some attributes may be
 220    returned to be applied at a later stage (for example, to apply
 221    a decl attribute to the declaration rather than to its type).  */
 222
 223 tree
 224 decl_attributes (tree *node, tree attributes, int flags)
 225 {
 226   tree a;
 227   tree returned_attrs = NULL_TREE;
 228
 229   if (TREE_TYPE (*node) == error_mark_node)
 230     return NULL_TREE;
 231
 232   if (!attributes_initialized)
 233     init_attributes ();
 234
 235   targetm.insert_attributes (*node, &attributes);
 236
 237   for (a = attributes; a; a = TREE_CHAIN (a))
 238     {
 239       tree name = TREE_PURPOSE (a);
 240       tree args = TREE_VALUE (a);
 241       tree *anode = node;
 242       const struct attribute_spec *spec = lookup_attribute_spec (name);
 243       bool no_add_attrs = 0;
 244       tree fn_ptr_tmp = NULL_TREE;
 245
 246       if (spec == NULL)
 247         {
 248           warning (OPT_Wattributes, "%qs attribute directive ignored",
 249                    IDENTIFIER_POINTER (name));
 250           continue;
 251         }
 252       else if (list_length (args) < spec->min_length
 253                || (spec->max_length >= 0
 254                    && list_length (args) > spec->max_length))
 255         {
 256           error ("wrong number of arguments specified for %qs attribute",
 257                  IDENTIFIER_POINTER (name));
 258           continue;
 259         }
 260       gcc_assert (is_attribute_p (spec->name, name));
 261
 262       if (spec->decl_required && !DECL_P (*anode))
 263         {
 264           if (flags & ((int) ATTR_FLAG_DECL_NEXT
 265                        | (int) ATTR_FLAG_FUNCTION_NEXT
 266                        | (int) ATTR_FLAG_ARRAY_NEXT))
 267             {
 268               /* Pass on this attribute to be tried again.  */
 269               returned_attrs = tree_cons (name, args, returned_attrs);
 270               continue;
 271             }
 272           else
 273             {
 274               warning (OPT_Wattributes, "%qs attribute does not apply to types",
 275                        IDENTIFIER_POINTER (name));
 276               continue;
 277             }
 278         }
 279
 280       /* If we require a type, but were passed a decl, set up to make a
 281          new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
 282          would have applied if we'd been passed a type, but we cannot modify
 283          the decl's type in place here.  */
 284       if (spec->type_required && DECL_P (*anode))
 285         {
 286           anode = &TREE_TYPE (*anode);
 287           /* Allow ATTR_FLAG_TYPE_IN_PLACE for the type's naming decl.  */
 288           if (!(TREE_CODE (*anode) == TYPE_DECL
 289                 && *anode == TYPE_NAME (TYPE_MAIN_VARIANT
 290                                         (TREE_TYPE (*anode)))))
 291             flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 292         }
 293
 294       if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
 295           && TREE_CODE (*anode) != METHOD_TYPE)
 296         {
 297           if (TREE_CODE (*anode) == POINTER_TYPE
 298               && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
 299                   || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
 300             {
 301               /* OK, this is a bit convoluted.  We can't just make a copy
 302                  of the pointer type and modify its TREE_TYPE, because if
 303                  we change the attributes of the target type the pointer
 304                  type needs to have a different TYPE_MAIN_VARIANT.  So we
 305                  pull out the target type now, frob it as appropriate, and
 306                  rebuild the pointer type later.
 307
 308                  This would all be simpler if attributes were part of the
 309                  declarator, grumble grumble.  */
 310               fn_ptr_tmp = TREE_TYPE (*anode);
 311               anode = &fn_ptr_tmp;
 312               flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 313             }
 314           else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
 315             {
 316               /* Pass on this attribute to be tried again.  */
 317               returned_attrs = tree_cons (name, args, returned_attrs);
 318               continue;
 319             }
 320
 321           if (TREE_CODE (*anode) != FUNCTION_TYPE
 322               && TREE_CODE (*anode) != METHOD_TYPE)
 323             {
 324               warning (OPT_Wattributes,
 325                        "%qs attribute only applies to function types",
 326                        IDENTIFIER_POINTER (name));
 327               continue;
 328             }
 329         }
 330
 331       if (TYPE_P (*anode)
 332           && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 333           && TYPE_SIZE (*anode) != NULL_TREE)
 334         {
 335           warning (OPT_Wattributes, "type attributes ignored after type is already defined");
 336           continue;
 337         }
 338
 339       if (spec->handler != NULL)
 340         returned_attrs = chainon ((*spec->handler) (anode, name, args,
 341                                                     flags, &no_add_attrs),
 342                                   returned_attrs);
 343
 344       /* Layout the decl in case anything changed.  */
 345       if (spec->type_required && DECL_P (*node)
 346           && (TREE_CODE (*node) == VAR_DECL
 347               || TREE_CODE (*node) == PARM_DECL
 348               || TREE_CODE (*node) == RESULT_DECL))
 349         relayout_decl (*node);
 350
 351       if (!no_add_attrs)
 352         {
 353           tree old_attrs;
 354           tree a;
 355
 356           if (DECL_P (*anode))
 357             old_attrs = DECL_ATTRIBUTES (*anode);
 358           else
 359             old_attrs = TYPE_ATTRIBUTES (*anode);
 360
 361           for (a = lookup_attribute (spec->name, old_attrs);
 362                a != NULL_TREE;
 363                a = lookup_attribute (spec->name, TREE_CHAIN (a)))
 364             {
 365               if (simple_cst_equal (TREE_VALUE (a), args) == 1)
 366                 break;
 367             }
 368
 369           if (a == NULL_TREE)
 370             {
 371               /* This attribute isn't already in the list.  */
 372               if (DECL_P (*anode))
 373                 DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 374               else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 375                 {
 376                   TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 377                   /* If this is the main variant, also push the attributes
 378                      out to the other variants.  */
 379                   if (*anode == TYPE_MAIN_VARIANT (*anode))
 380                     {
 381                       tree variant;
 382                       for (variant = *anode; variant;
 383                            variant = TYPE_NEXT_VARIANT (variant))
 384                         {
 385                           if (TYPE_ATTRIBUTES (variant) == old_attrs)
 386                             TYPE_ATTRIBUTES (variant)
 387                               = TYPE_ATTRIBUTES (*anode);
 388                           else if (!lookup_attribute
 389                                    (spec->name, TYPE_ATTRIBUTES (variant)))
 390                             TYPE_ATTRIBUTES (variant) = tree_cons
 391                               (name, args, TYPE_ATTRIBUTES (variant));
 392                         }
 393                     }
 394                 }
 395               else
 396                 *anode = build_type_attribute_variant (*anode,
 397                                                        tree_cons (name, args,
 398                                                                   old_attrs));
 399             }
 400         }
 401
 402       if (fn_ptr_tmp)
 403         {
 404           /* Rebuild the function pointer type and put it in the
 405              appropriate place.  */
 406           fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
 407           if (DECL_P (*node))
 408             TREE_TYPE (*node) = fn_ptr_tmp;
 409           else
 410             {
 411               gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
 412               *node = fn_ptr_tmp;
 413             }
 414         }
 415     }
 416
 417   return returned_attrs;
 418 }