gcc/attribs.c

   1 /* Functions dealing with attribute handling, used by most front ends.
   2    Copyright (C) 1992-2014 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "tree.h"
  25 #include "stringpool.h"
  26 #include "attribs.h"
  27 #include "stor-layout.h"
  28 #include "flags.h"
  29 #include "diagnostic-core.h"
  30 #include "ggc.h"
  31 #include "tm_p.h"
  32 #include "cpplib.h"
  33 #include "target.h"
  34 #include "langhooks.h"
  35 #include "hash-table.h"
  36 #include "plugin.h"
  37
  38 /* Table of the tables of attributes (common, language, format, machine)
  39    searched.  */
  40 static const struct attribute_spec *attribute_tables[4];
  41
  42 /* Substring representation.  */
  43
  44 struct substring
  45 {
  46   const char *str;
  47   int length;
  48 };
  49
  50 /* Simple hash function to avoid need to scan whole string.  */
  51
  52 static inline hashval_t
  53 substring_hash (const char *str, int l)
  54 {
  55   return str[0] + str[l - 1] * 256 + l * 65536;
  56 }
  57
  58 /* Used for attribute_hash.  */
  59
  60 struct attribute_hasher : typed_noop_remove <attribute_spec>
  61 {
  62   typedef attribute_spec value_type;
  63   typedef substring compare_type;
  64   static inline hashval_t hash (const value_type *);
  65   static inline bool equal (const value_type *, const compare_type *);
  66 };
  67
  68 inline hashval_t
  69 attribute_hasher::hash (const value_type *spec)
  70 {
  71   const int l = strlen (spec->name);
  72   return substring_hash (spec->name, l);
  73 }
  74
  75 inline bool
  76 attribute_hasher::equal (const value_type *spec, const compare_type *str)
  77 {
  78   return (strncmp (spec->name, str->str, str->length) == 0
  79           && !spec->name[str->length]);
  80 }
  81
  82 /* Scoped attribute name representation.  */
  83
  84 struct scoped_attributes
  85 {
  86   const char *ns;
  87   vec<attribute_spec> attributes;
  88   hash_table<attribute_hasher> *attribute_hash;
  89 };
  90
  91 /* The table of scope attributes.  */
  92 static vec<scoped_attributes> attributes_table;
  93
  94 static scoped_attributes* find_attribute_namespace (const char*);
  95 static void register_scoped_attribute (const struct attribute_spec *,
  96                                        scoped_attributes *);
  97
  98 static bool attributes_initialized = false;
  99
 100 /* Default empty table of attributes.  */
 101
 102 static const struct attribute_spec empty_attribute_table[] =
 103 {
 104   { NULL, 0, 0, false, false, false, NULL, false }
 105 };
 106
 107 /* Return base name of the attribute.  Ie '__attr__' is turned into 'attr'.
 108    To avoid need for copying, we simply return length of the string.  */
 109
 110 static void
 111 extract_attribute_substring (struct substring *str)
 112 {
 113   if (str->length > 4 && str->str[0] == '_' && str->str[1] == '_'
 114       && str->str[str->length - 1] == '_' && str->str[str->length - 2] == '_')
 115     {
 116       str->length -= 4;
 117       str->str += 2;
 118     }
 119 }
 120
 121 /* Insert an array of attributes ATTRIBUTES into a namespace.  This
 122    array must be NULL terminated.  NS is the name of attribute
 123    namespace.  The function returns the namespace into which the
 124    attributes have been registered.  */
 125
 126 scoped_attributes*
 127 register_scoped_attributes (const struct attribute_spec * attributes,
 128                             const char* ns)
 129 {
 130   scoped_attributes *result = NULL;
 131
 132   /* See if we already have attributes in the namespace NS.  */
 133   result = find_attribute_namespace (ns);
 134
 135   if (result == NULL)
 136     {
 137       /* We don't have any namespace NS yet.  Create one.  */
 138       scoped_attributes sa;
 139
 140       if (!attributes_table.is_empty ())
 141         attributes_table.create (64);
 142
 143       memset (&sa, 0, sizeof (sa));
 144       sa.ns = ns;
 145       sa.attributes.create (64);
 146       result = attributes_table.safe_push (sa);
 147       result->attribute_hash = new hash_table<attribute_hasher> (200);
 148     }
 149
 150   /* Really add the attributes to their namespace now.  */
 151   for (unsigned i = 0; attributes[i].name != NULL; ++i)
 152     {
 153       result->attributes.safe_push (attributes[i]);
 154       register_scoped_attribute (&attributes[i], result);
 155     }
 156
 157   gcc_assert (result != NULL);
 158
 159   return result;
 160 }
 161
 162 /* Return the namespace which name is NS, NULL if none exist.  */
 163
 164 static scoped_attributes*
 165 find_attribute_namespace (const char* ns)
 166 {
 167   unsigned ix;
 168   scoped_attributes *iter;
 169
 170   FOR_EACH_VEC_ELT (attributes_table, ix, iter)
 171     if (ns == iter->ns
 172         || (iter->ns != NULL
 173             && ns != NULL
 174             && !strcmp (iter->ns, ns)))
 175       return iter;
 176   return NULL;
 177 }
 178
 179 /* Initialize attribute tables, and make some sanity checks
 180    if --enable-checking.  */
 181
 182 void
 183 init_attributes (void)
 184 {
 185   size_t i;
 186
 187   if (attributes_initialized)
 188     return;
 189
 190   attribute_tables[0] = lang_hooks.common_attribute_table;
 191   attribute_tables[1] = lang_hooks.attribute_table;
 192   attribute_tables[2] = lang_hooks.format_attribute_table;
 193   attribute_tables[3] = targetm.attribute_table;
 194
 195   /* Translate NULL pointers to pointers to the empty table.  */
 196   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 197     if (attribute_tables[i] == NULL)
 198       attribute_tables[i] = empty_attribute_table;
 199
 200 #ifdef ENABLE_CHECKING
 201   /* Make some sanity checks on the attribute tables.  */
 202   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 203     {
 204       int j;
 205
 206       for (j = 0; attribute_tables[i][j].name != NULL; j++)
 207         {
 208           /* The name must not begin and end with __.  */
 209           const char *name = attribute_tables[i][j].name;
 210           int len = strlen (name);
 211
 212           gcc_assert (!(name[0] == '_' && name[1] == '_'
 213                         && name[len - 1] == '_' && name[len - 2] == '_'));
 214
 215           /* The minimum and maximum lengths must be consistent.  */
 216           gcc_assert (attribute_tables[i][j].min_length >= 0);
 217
 218           gcc_assert (attribute_tables[i][j].max_length == -1
 219                       || (attribute_tables[i][j].max_length
 220                           >= attribute_tables[i][j].min_length));
 221
 222           /* An attribute cannot require both a DECL and a TYPE.  */
 223           gcc_assert (!attribute_tables[i][j].decl_required
 224                       || !attribute_tables[i][j].type_required);
 225
 226           /* If an attribute requires a function type, in particular
 227              it requires a type.  */
 228           gcc_assert (!attribute_tables[i][j].function_type_required
 229                       || attribute_tables[i][j].type_required);
 230         }
 231     }
 232
 233   /* Check that each name occurs just once in each table.  */
 234   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 235     {
 236       int j, k;
 237       for (j = 0; attribute_tables[i][j].name != NULL; j++)
 238         for (k = j + 1; attribute_tables[i][k].name != NULL; k++)
 239           gcc_assert (strcmp (attribute_tables[i][j].name,
 240                               attribute_tables[i][k].name));
 241     }
 242   /* Check that no name occurs in more than one table.  Names that
 243      begin with '*' are exempt, and may be overridden.  */
 244   for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
 245     {
 246       size_t j, k, l;
 247
 248       for (j = i + 1; j < ARRAY_SIZE (attribute_tables); j++)
 249         for (k = 0; attribute_tables[i][k].name != NULL; k++)
 250           for (l = 0; attribute_tables[j][l].name != NULL; l++)
 251             gcc_assert (attribute_tables[i][k].name[0] == '*'
 252                         || strcmp (attribute_tables[i][k].name,
 253                                    attribute_tables[j][l].name));
 254     }
 255 #endif
 256
 257   for (i = 0; i < ARRAY_SIZE (attribute_tables); ++i)
 258     /* Put all the GNU attributes into the "gnu" namespace.  */
 259     register_scoped_attributes (attribute_tables[i], "gnu");
 260
 261   invoke_plugin_callbacks (PLUGIN_ATTRIBUTES, NULL);
 262   attributes_initialized = true;
 263 }
 264
 265 /* Insert a single ATTR into the attribute table.  */
 266
 267 void
 268 register_attribute (const struct attribute_spec *attr)
 269 {
 270   register_scoped_attribute (attr, find_attribute_namespace ("gnu"));
 271 }
 272
 273 /* Insert a single attribute ATTR into a namespace of attributes.  */
 274
 275 static void
 276 register_scoped_attribute (const struct attribute_spec *attr,
 277                            scoped_attributes *name_space)
 278 {
 279   struct substring str;
 280   attribute_spec **slot;
 281
 282   gcc_assert (attr != NULL && name_space != NULL);
 283
 284   gcc_assert (name_space->attribute_hash);
 285
 286   str.str = attr->name;
 287   str.length = strlen (str.str);
 288
 289   /* Attribute names in the table must be in the form 'text' and not
 290      in the form '__text__'.  */
 291   gcc_assert (str.length > 0 && str.str[0] != '_');
 292
 293   slot = name_space->attribute_hash
 294          ->find_slot_with_hash (&str, substring_hash (str.str, str.length),
 295                                 INSERT);
 296   gcc_assert (!*slot || attr->name[0] == '*');
 297   *slot = CONST_CAST (struct attribute_spec *, attr);
 298 }
 299
 300 /* Return the spec for the scoped attribute with namespace NS and
 301    name NAME.   */
 302
 303 static const struct attribute_spec *
 304 lookup_scoped_attribute_spec (const_tree ns, const_tree name)
 305 {
 306   struct substring attr;
 307   scoped_attributes *attrs;
 308
 309   const char *ns_str = (ns != NULL_TREE) ? IDENTIFIER_POINTER (ns): NULL;
 310
 311   attrs = find_attribute_namespace (ns_str);
 312
 313   if (attrs == NULL)
 314     return NULL;
 315
 316   attr.str = IDENTIFIER_POINTER (name);
 317   attr.length = IDENTIFIER_LENGTH (name);
 318   extract_attribute_substring (&attr);
 319   return attrs->attribute_hash->find_with_hash (&attr,
 320                                                 substring_hash (attr.str,
 321                                                                 attr.length));
 322 }
 323
 324 /* Return the spec for the attribute named NAME.  If NAME is a TREE_LIST,
 325    it also specifies the attribute namespace.  */
 326
 327 const struct attribute_spec *
 328 lookup_attribute_spec (const_tree name)
 329 {
 330   tree ns;
 331   if (TREE_CODE (name) == TREE_LIST)
 332     {
 333       ns = TREE_PURPOSE (name);
 334       name = TREE_VALUE (name);
 335     }
 336   else
 337     ns = get_identifier ("gnu");
 338   return lookup_scoped_attribute_spec (ns, name);
 339 }
 340
 341
 342 /* Return the namespace of the attribute ATTR.  This accessor works on
 343    GNU and C++11 (scoped) attributes.  On GNU attributes,
 344    it returns an identifier tree for the string "gnu".
 345
 346    Please read the comments of cxx11_attribute_p to understand the
 347    format of attributes.  */
 348
 349 static tree
 350 get_attribute_namespace (const_tree attr)
 351 {
 352   if (cxx11_attribute_p (attr))
 353     return TREE_PURPOSE (TREE_PURPOSE (attr));
 354   return get_identifier ("gnu");
 355 }
 356
 357
 358 /* Process the attributes listed in ATTRIBUTES and install them in *NODE,
 359    which is either a DECL (including a TYPE_DECL) or a TYPE.  If a DECL,
 360    it should be modified in place; if a TYPE, a copy should be created
 361    unless ATTR_FLAG_TYPE_IN_PLACE is set in FLAGS.  FLAGS gives further
 362    information, in the form of a bitwise OR of flags in enum attribute_flags
 363    from tree.h.  Depending on these flags, some attributes may be
 364    returned to be applied at a later stage (for example, to apply
 365    a decl attribute to the declaration rather than to its type).  */
 366
 367 tree
 368 decl_attributes (tree *node, tree attributes, int flags)
 369 {
 370   tree a;
 371   tree returned_attrs = NULL_TREE;
 372
 373   if (TREE_TYPE (*node) == error_mark_node || attributes == error_mark_node)
 374     return NULL_TREE;
 375
 376   if (!attributes_initialized)
 377     init_attributes ();
 378
 379   /* If this is a function and the user used #pragma GCC optimize, add the
 380      options to the attribute((optimize(...))) list.  */
 381   if (TREE_CODE (*node) == FUNCTION_DECL && current_optimize_pragma)
 382     {
 383       tree cur_attr = lookup_attribute ("optimize", attributes);
 384       tree opts = copy_list (current_optimize_pragma);
 385
 386       if (! cur_attr)
 387         attributes
 388           = tree_cons (get_identifier ("optimize"), opts, attributes);
 389       else
 390         TREE_VALUE (cur_attr) = chainon (opts, TREE_VALUE (cur_attr));
 391     }
 392
 393   if (TREE_CODE (*node) == FUNCTION_DECL
 394       && optimization_current_node != optimization_default_node
 395       && !DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node))
 396     DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node) = optimization_current_node;
 397
 398   /* If this is a function and the user used #pragma GCC target, add the
 399      options to the attribute((target(...))) list.  */
 400   if (TREE_CODE (*node) == FUNCTION_DECL
 401       && current_target_pragma
 402       && targetm.target_option.valid_attribute_p (*node, NULL_TREE,
 403                                                   current_target_pragma, 0))
 404     {
 405       tree cur_attr = lookup_attribute ("target", attributes);
 406       tree opts = copy_list (current_target_pragma);
 407
 408       if (! cur_attr)
 409         attributes = tree_cons (get_identifier ("target"), opts, attributes);
 410       else
 411         TREE_VALUE (cur_attr) = chainon (opts, TREE_VALUE (cur_attr));
 412     }
 413
 414   /* A "naked" function attribute implies "noinline" and "noclone" for
 415      those targets that support it.  */
 416   if (TREE_CODE (*node) == FUNCTION_DECL
 417       && attributes
 418       && lookup_attribute_spec (get_identifier ("naked"))
 419       && lookup_attribute ("naked", attributes) != NULL)
 420     {
 421       if (lookup_attribute ("noinline", attributes) == NULL)
 422         attributes = tree_cons (get_identifier ("noinline"), NULL, attributes);
 423
 424       if (lookup_attribute ("noclone", attributes) == NULL)
 425         attributes = tree_cons (get_identifier ("noclone"),  NULL, attributes);
 426     }
 427
 428   targetm.insert_attributes (*node, &attributes);
 429
 430   for (a = attributes; a; a = TREE_CHAIN (a))
 431     {
 432       tree ns = get_attribute_namespace (a);
 433       tree name = get_attribute_name (a);
 434       tree args = TREE_VALUE (a);
 435       tree *anode = node;
 436       const struct attribute_spec *spec =
 437         lookup_scoped_attribute_spec (ns, name);
 438       bool no_add_attrs = 0;
 439       int fn_ptr_quals = 0;
 440       tree fn_ptr_tmp = NULL_TREE;
 441
 442       if (spec == NULL)
 443         {
 444           if (!(flags & (int) ATTR_FLAG_BUILT_IN))
 445             {
 446               if (ns == NULL_TREE || !cxx11_attribute_p (a))
 447                 warning (OPT_Wattributes, "%qE attribute directive ignored",
 448                          name);
 449               else
 450                 warning (OPT_Wattributes,
 451                          "%<%E::%E%> scoped attribute directive ignored",
 452                          ns, name);
 453             }
 454           continue;
 455         }
 456       else if (list_length (args) < spec->min_length
 457                || (spec->max_length >= 0
 458                    && list_length (args) > spec->max_length))
 459         {
 460           error ("wrong number of arguments specified for %qE attribute",
 461                  name);
 462           continue;
 463         }
 464       gcc_assert (is_attribute_p (spec->name, name));
 465
 466       if (TYPE_P (*node)
 467           && cxx11_attribute_p (a)
 468           && !(flags & ATTR_FLAG_TYPE_IN_PLACE))
 469         {
 470           /* This is a c++11 attribute that appertains to a
 471              type-specifier, outside of the definition of, a class
 472              type.  Ignore it.  */
 473           warning (OPT_Wattributes, "attribute ignored");
 474           inform (input_location,
 475                   "an attribute that appertains to a type-specifier "
 476                   "is ignored");
 477           continue;
 478         }
 479
 480       if (spec->decl_required && !DECL_P (*anode))
 481         {
 482           if (flags & ((int) ATTR_FLAG_DECL_NEXT
 483                        | (int) ATTR_FLAG_FUNCTION_NEXT
 484                        | (int) ATTR_FLAG_ARRAY_NEXT))
 485             {
 486               /* Pass on this attribute to be tried again.  */
 487               returned_attrs = tree_cons (name, args, returned_attrs);
 488               continue;
 489             }
 490           else
 491             {
 492               warning (OPT_Wattributes, "%qE attribute does not apply to types",
 493                        name);
 494               continue;
 495             }
 496         }
 497
 498       /* If we require a type, but were passed a decl, set up to make a
 499          new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
 500          would have applied if we'd been passed a type, but we cannot modify
 501          the decl's type in place here.  */
 502       if (spec->type_required && DECL_P (*anode))
 503         {
 504           anode = &TREE_TYPE (*anode);
 505           /* Allow ATTR_FLAG_TYPE_IN_PLACE for the type's naming decl.  */
 506           if (!(TREE_CODE (*anode) == TYPE_DECL
 507                 && *anode == TYPE_NAME (TYPE_MAIN_VARIANT
 508                                         (TREE_TYPE (*anode)))))
 509             flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 510         }
 511
 512       if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
 513           && TREE_CODE (*anode) != METHOD_TYPE)
 514         {
 515           if (TREE_CODE (*anode) == POINTER_TYPE
 516               && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
 517                   || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
 518             {
 519               /* OK, this is a bit convoluted.  We can't just make a copy
 520                  of the pointer type and modify its TREE_TYPE, because if
 521                  we change the attributes of the target type the pointer
 522                  type needs to have a different TYPE_MAIN_VARIANT.  So we
 523                  pull out the target type now, frob it as appropriate, and
 524                  rebuild the pointer type later.
 525
 526                  This would all be simpler if attributes were part of the
 527                  declarator, grumble grumble.  */
 528               fn_ptr_tmp = TREE_TYPE (*anode);
 529               fn_ptr_quals = TYPE_QUALS (*anode);
 530               anode = &fn_ptr_tmp;
 531               flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
 532             }
 533           else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
 534             {
 535               /* Pass on this attribute to be tried again.  */
 536               returned_attrs = tree_cons (name, args, returned_attrs);
 537               continue;
 538             }
 539
 540           if (TREE_CODE (*anode) != FUNCTION_TYPE
 541               && TREE_CODE (*anode) != METHOD_TYPE)
 542             {
 543               warning (OPT_Wattributes,
 544                        "%qE attribute only applies to function types",
 545                        name);
 546               continue;
 547             }
 548         }
 549
 550       if (TYPE_P (*anode)
 551           && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 552           && TYPE_SIZE (*anode) != NULL_TREE)
 553         {
 554           warning (OPT_Wattributes, "type attributes ignored after type is already defined");
 555           continue;
 556         }
 557
 558       if (spec->handler != NULL)
 559         {
 560           int cxx11_flag =
 561             cxx11_attribute_p (a) ? ATTR_FLAG_CXX11 : 0;
 562
 563           returned_attrs = chainon ((*spec->handler) (anode, name, args,
 564                                                       flags|cxx11_flag,
 565                                                       &no_add_attrs),
 566                                     returned_attrs);
 567         }
 568
 569       /* Layout the decl in case anything changed.  */
 570       if (spec->type_required && DECL_P (*node)
 571           && (TREE_CODE (*node) == VAR_DECL
 572               || TREE_CODE (*node) == PARM_DECL
 573               || TREE_CODE (*node) == RESULT_DECL))
 574         relayout_decl (*node);
 575
 576       if (!no_add_attrs)
 577         {
 578           tree old_attrs;
 579           tree a;
 580
 581           if (DECL_P (*anode))
 582             old_attrs = DECL_ATTRIBUTES (*anode);
 583           else
 584             old_attrs = TYPE_ATTRIBUTES (*anode);
 585
 586           for (a = lookup_attribute (spec->name, old_attrs);
 587                a != NULL_TREE;
 588                a = lookup_attribute (spec->name, TREE_CHAIN (a)))
 589             {
 590               if (simple_cst_equal (TREE_VALUE (a), args) == 1)
 591                 break;
 592             }
 593
 594           if (a == NULL_TREE)
 595             {
 596               /* This attribute isn't already in the list.  */
 597               if (DECL_P (*anode))
 598                 DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 599               else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
 600                 {
 601                   TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
 602                   /* If this is the main variant, also push the attributes
 603                      out to the other variants.  */
 604                   if (*anode == TYPE_MAIN_VARIANT (*anode))
 605                     {
 606                       tree variant;
 607                       for (variant = *anode; variant;
 608                            variant = TYPE_NEXT_VARIANT (variant))
 609                         {
 610                           if (TYPE_ATTRIBUTES (variant) == old_attrs)
 611                             TYPE_ATTRIBUTES (variant)
 612                               = TYPE_ATTRIBUTES (*anode);
 613                           else if (!lookup_attribute
 614                                    (spec->name, TYPE_ATTRIBUTES (variant)))
 615                             TYPE_ATTRIBUTES (variant) = tree_cons
 616                               (name, args, TYPE_ATTRIBUTES (variant));
 617                         }
 618                     }
 619                 }
 620               else
 621                 *anode = build_type_attribute_variant (*anode,
 622                                                        tree_cons (name, args,
 623                                                                   old_attrs));
 624             }
 625         }
 626
 627       if (fn_ptr_tmp)
 628         {
 629           /* Rebuild the function pointer type and put it in the
 630              appropriate place.  */
 631           fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
 632           if (fn_ptr_quals)
 633             fn_ptr_tmp = build_qualified_type (fn_ptr_tmp, fn_ptr_quals);
 634           if (DECL_P (*node))
 635             TREE_TYPE (*node) = fn_ptr_tmp;
 636           else
 637             {
 638               gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
 639               *node = fn_ptr_tmp;
 640             }
 641         }
 642     }
 643
 644   return returned_attrs;
 645 }
 646
 647 /* Return TRUE iff ATTR has been parsed by the front-end as a C++-11
 648    attribute.
 649
 650    When G++ parses a C++11 attribute, it is represented as
 651    a TREE_LIST which TREE_PURPOSE is itself a TREE_LIST.  TREE_PURPOSE
 652    (TREE_PURPOSE (ATTR)) is the namespace of the attribute, and the
 653    TREE_VALUE (TREE_PURPOSE (ATTR)) is its non-qualified name.  Please
 654    use get_attribute_namespace and get_attribute_name to retrieve the
 655    namespace and name of the attribute, as these accessors work with
 656    GNU attributes as well.  */
 657
 658 bool
 659 cxx11_attribute_p (const_tree attr)
 660 {
 661   if (attr == NULL_TREE
 662       || TREE_CODE (attr) != TREE_LIST)
 663     return false;
 664
 665   return (TREE_CODE (TREE_PURPOSE (attr)) == TREE_LIST);
 666 }
 667
 668 /* Return the name of the attribute ATTR.  This accessor works on GNU
 669    and C++11 (scoped) attributes.
 670
 671    Please read the comments of cxx11_attribute_p to understand the
 672    format of attributes.  */
 673
 674 tree
 675 get_attribute_name (const_tree attr)
 676 {
 677   if (cxx11_attribute_p (attr))
 678     return TREE_VALUE (TREE_PURPOSE (attr));
 679   return TREE_PURPOSE (attr);
 680 }
 681
 682 /* Subroutine of set_method_tm_attributes.  Apply TM attribute ATTR
 683    to the method FNDECL.  */
 684
 685 void
 686 apply_tm_attr (tree fndecl, tree attr)
 687 {
 688   decl_attributes (&TREE_TYPE (fndecl), tree_cons (attr, NULL, NULL), 0);
 689 }