PR c++/53528 C++11 attribute support

This patch implements the c++-11 generalized attributes, described in
the N2761 paper[1].

The idea is to modify the front-end to accept the new attribute syntax
(including alignas expressions) and to build an internal
representation similar to the one we already have for GNU attributes.

This lets us re-use our existing GNU attribute mechanisms to support
the generalized c++11 attributes.

The patch does change the existing internal representation to support
scoped attribute (aka attributes with namespaces), which is a concept
that doesn't exist in GNU attributes.  I have thus put all existing
GNU extension attributes into the "gnu" namespace.  For instance, in
C++-11, the "unused" attribute would be represented as
"[[gnu::unused]]".  Because there is no syntax for scoped attributes
in C, writting "__attribute__((unused))" unconditionnally refers to
the "unused" attribute in the "gnu" namespace.

Note that this patch follows a conservative understanding of the
specification by disallowing attributes appertaining to types, unless
they apply to a type definition.

Tested on x86_64-unknown-linux-gnu and powerpc64-unknown-linux-gnu.

[1]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2761.pdf

gcc/
	* plugin.h (register_scoped_attributes): Declare new function.
	* tree.h (enu attribute_flags::ATTR_FLAG_CXX_11): New flag.
	(lookup_scoped_attribute_spec, cxx_11_attribute_p)
	(get_attribute_name, get_attribute_namespace): Declare new functions.
	(struct attribute_spec): Remove const qualifier from the members.
	* tree.c (comp_type_attributes, private_lookup_attribute)
	(lookup_ident_attribute, remove_attribute, merge_attribute)
	(attribute_hash_list, attribute_list_contained): Use
	get_attribute_name.
	* attribs.c (decl_attributes): Don't crash on error_mark_node.
	Forbid c++11 attributes appertaining to type-specifiers.
	(attribute_hash): Remove global variable.
	(attributes_table): New global variable.
	(find_attribute_namespace, register_scoped_attribute): New static
	functions.
	(register_scoped_attributes, lookup_scoped_attribute_spec)
	(cxx11_attribute_p, get_attribute_name, get_attribute_namespace):
	New public functions.
	(init_attributes): Register all the GNU attributes into the "gnu"
	namespace.
	(register_attribute): Use register_scoped_attribute to register
	the attribute into the "gnu" namespace.
	(lookup_attribute_spec): Use lookup_scoped_attribute_spec to
	lookup the attribute in the "gnu" namespace.
	(decl_attributes): Use new get_attribute_namespace and
	lookup_scoped_attribute_spec to consider attribute namespaces when
	looking up attributes.  When operating in c++-11 mode, pass flag
	ATTR_FLAG_CXX11 to the spec handler.

gcc/c-family/

	* c-common.h (bitfield_p, cxx_fundamental_alignment_p): Declare
	new functions.
	* c-common.c (check_cxx_fundamental_alignment_constraints): New
	static function.
	(handle_aligned_attribute): In choose strictest alignment
	among many.  Use new check_cxx_fundamental_alignment_constraints.
	(handle_transparent_union_attribute): In c++11 attribute syntax,
	don't look through typedefs.

gcc/cp/

	* cp-tree.h (enum cpp0x_warn_str::CPP0X_ATTRIBUTES): New member.
	(enum cp_decl_spec::ds_std_attribute): New enumerator.
	(struct cp_decl_specifier_seq::std_attributes): New field.
	(cxx_alignas_expr, warn_misplaced_attr_for_class_type): Declare
	new functions.
	(check_tag_decl): Take an extra parameter for explicit
	instantiations.
	* decl.c (warn_misplaced_attr_for_class_type): Extract from ...
	(check_tag_decl): ... here.  Add check for c++11 attributes being
	applied to an explicit instantiation.  Take an extra parameter for
	explicit instantiations.
	(grokdeclarator): Make sure a c++11 attribute after an array
	declarator appertains to the array, an attribute after a function
	declarator appertains to the function type, an attribute after a
	declarator-id appertains to the entity being declared, and an
	attribute after a pointer declarator appertains to the pointer.
	* decl2.c (is_late_template_attribute): Use get_attribute_name.
	* error.c (maybe_warn_cpp0x): Support
	CPP0X_GENERALIZED_ATTRIBUTES.
	* parser.c (cp_next_tokens_can_be_attribute_p)
	(cp_next_tokens_can_be_gnu_attribute_p)
	(cp_next_tokens_can_be_std_attribute_p)
	(cp_nth_tokens_can_be_attribute_p)
	(cp_nth_tokens_can_be_gnu_attribute_p)
	(cp_nth_tokens_can_be_std_attribute_p)
	(cp_parser_gnu_attribute_list, cp_parser_std_attribute)
	(cp_parser_std_attribute_spec, cp_parser_std_attribute_spec_seq)
	(cp_parser_attributes_opt, cp_parser_std_attribute_list): New
	static functions.
	(cp_parser_gnu_attributes_opt): Replace cp_parser_attributes_opt.
	(cp_parser_gnu_attribute_list): Replace cp_parser_attribute_list.
	(cp_parser_postfix_expression): Disallow "[[" tokens here.
	(cp_parser_label_for_labeled_statement): Use take an extra
	parameter for attributes.
	(cp_parser_block_declaration): Use
	cp_nth_tokens_can_be_std_attribute_p here.
	(cp_parser_decl_specifier_seq): Likewise.  Store C++11 attributes
	that appears in in decl specifiers in cp_decl_specifier_seq::std_attributes.
	declaration.  Emit proper warning about misplaced c++11 attributes
	for class type.
	(cp_parser_explicit_instantiation): Adjust call to check_tag_decl.
	(cp_parser_init_declarator):  Parsing attributes here is no more a
	GNU extension in c++-11.
	(cp_parser_type_specifier_seq): Use
	cp_next_tokens_can_be_attribute_p.
	(cp_parser_direct_declarator): Likewise.  Hang c++11 attributes
	following the declarator to its syntactic construct.  It'll later
	be applied to the proper appertaining entity by grokdeclarator.
	(cp_parser_ptr_operator): Likewise.
	(make_declarator): Initialize cp_declarator::std_attribute.
	(make_pointer_declarator, make_reference_declarator)
	(make_ptrmem_declarator, cp_parser_make_indirect_declarator): Take
	attributes that appertain to the pointer/reference in argument.
	(cp_parser_ptr_operator): Take an out parameter for c++11
	attributes.  Update comments.
	(cp_parser_new_declarator_opt)
	(cp_parser_conversion_declarator_opt): Adjust.
	(cp_parser_declarator): Likewise.  Handle C++11 attributes.
	Rename attributes to gnu_attribute for better legibility.
	(cp_parser_simple_declaration): Update comment.
	(cp_parser_class_specifier_1): Parse GNU attributes specifically
	(cp_parser_enum_specifier): Accept only gnu attributes after the
	specifier.
	(cp_parser_member_declaration): Don't clear attributes -- intended
	for the entity being declared -- too early because check_tag_decl
	needs them.
	(cp_parser_statement): Update comment.  Parse optional c++11
	attributes at the beginning of the relevant kind of statements and
	ignore them, for now, unless when calling
	cp_parser_label_for_labeled_statement.
	(cp_parser_label_for_labeled_statement): Take c++11 attributes
	in parameter.
	* semantics.c (potential_constant_expression_1): Likewise.
	* typeck.c (fundamental_alignment_p, cxx_alignas_expr): New public
	functions.

gcc/testsuite/

	* g++.dg/cpp0x/gen-attrs-1.C: New test.
	* g++.dg/cpp0x/gen-attrs-2.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-2-1.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-3.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-4.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-5.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-6.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-7.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-8.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-9.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-10.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-11.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-12.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-13.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-14.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-15.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-16.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-17.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-18.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-19.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-20.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-21.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-22.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-23.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-24.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-25.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-26.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-27.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-28.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-29.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-30.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-31.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-32.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-33.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-34.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-35.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-36.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-36-1.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-37.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-38.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-39.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-39-1.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-40.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-41.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-42.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-43.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-44.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-45.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-46.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-47.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-47-1.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-48.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-49.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-50.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-51.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-52.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-53.C: Likewise.

From-SVN: r192199

3 files changed, 131 insertions, 2 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 0d112cf..b49388d 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,15 @@
+2012-10-08  Dodji Seketeli  <dodji@redhat.com>
+
+	PR c++/53528 C++11 attribute support
+	* c-common.h (bitfield_p, cxx_fundamental_alignment_p): Declare
+	new functions.
+	* c-common.c (check_cxx_fundamental_alignment_constraints): New
+	static function.
+	(handle_aligned_attribute): In choose strictest alignment
+	among many.  Use new check_cxx_fundamental_alignment_constraints.
+	(handle_transparent_union_attribute): In c++11 attribute syntax,
+	don't look through typedefs.
+
 2012-10-04  Arnaud Charlet  <charlet@adacore.com>
 
 	* c-ada-spec.c (print_ada_declaration): Remove handling of TDF_RAW.
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 6de2f1c..e242789 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -484,6 +484,7 @@ const struct c_common_resword c_common_reswords[] =
   { "__underlying_type", RID_UNDERLYING_TYPE, D_CXXONLY },
   { "__volatile",	RID_VOLATILE,	0 },
   { "__volatile__",	RID_VOLATILE,	0 },
+  { "alignas",		RID_ALIGNAS,	D_CXXONLY | D_CXX0X | D_CXXWARN },
   { "alignof",		RID_ALIGNOF,	D_CXXONLY | D_CXX0X | D_CXXWARN },
   { "asm",		RID_ASM,	D_ASM },
   { "auto",		RID_AUTO,	0 },
@@ -6665,7 +6666,9 @@ handle_transparent_union_attribute (tree *node, tree name,
 
   *no_add_attrs = true;
 
-  if (TREE_CODE (*node) == TYPE_DECL)
+
+  if (TREE_CODE (*node) == TYPE_DECL
+      && ! (flags & ATTR_FLAG_CXX11))
     node = &TREE_TYPE (*node);
   type = *node;
 
@@ -7137,6 +7140,89 @@ check_user_alignment (const_tree align, bool allow_zero)
   return i;
 }
 
+/* 
+   If in c++-11, check if the c++-11 alignment constraint with respect
+   to fundamental alignment (in [dcl.align]) are satisfied.  If not in
+   c++-11 mode, does nothing.
+
+   [dcl.align]2/ says:
+
+   [* if the constant expression evaluates to a fundamental alignment,
+   the alignment requirement of the declared entity shall be the
+   specified fundamental alignment.
+
+   * if the constant expression evaluates to an extended alignment
+   and the implementation supports that alignment in the context
+   of the declaration, the alignment of the declared entity shall
+   be that alignment
+
+   * if the constant expression evaluates to an extended alignment
+   and the implementation does not support that alignment in the
+   context of the declaration, the program is ill-formed].  */
+
+static bool
+check_cxx_fundamental_alignment_constraints (tree node,
+					     unsigned align_log,
+					     int flags)
+{
+  bool alignment_too_large_p = false;
+  unsigned requested_alignment = 1U << align_log;
+  unsigned max_align = 0;
+
+  if ((!(flags & ATTR_FLAG_CXX11) && !warn_cxx_compat)
+      || (node == NULL_TREE || node == error_mark_node))
+    return true;
+
+  if (cxx_fundamental_alignment_p (requested_alignment))
+    return true;
+
+  if (DECL_P (node))
+    {
+      if (TREE_STATIC (node))
+	{
+	  /* For file scope variables and static members, the target
+	     supports alignments that are at most
+	     MAX_OFILE_ALIGNMENT.  */
+	  if (requested_alignment > (max_align = MAX_OFILE_ALIGNMENT))
+	    alignment_too_large_p = true;
+	}
+      else
+	{
+#ifdef BIGGEST_FIELD_ALIGNMENT
+#define MAX_TARGET_FIELD_ALIGNMENT BIGGEST_FIELD_ALIGNMENT
+#else
+#define MAX_TARGET_FIELD_ALIGNMENT BIGGEST_ALIGNMENT
+#endif
+	  /* For non-static members, the target supports either
+	     alignments that at most either BIGGEST_FIELD_ALIGNMENT
+	     if it is defined or BIGGEST_ALIGNMENT.  */
+	  max_align = MAX_TARGET_FIELD_ALIGNMENT;
+	  if (TREE_CODE (node) == FIELD_DECL
+	      && requested_alignment > (max_align = MAX_TARGET_FIELD_ALIGNMENT))
+	    alignment_too_large_p = true;
+#undef MAX_TARGET_FIELD_ALIGNMENT
+	  /* For stack variables, the target supports at most
+	     MAX_STACK_ALIGNMENT.  */
+	  else if (decl_function_context (node) != NULL
+		   && requested_alignment > (max_align = MAX_STACK_ALIGNMENT))
+	    alignment_too_large_p = true;
+	}
+    }
+  else if (TYPE_P (node))
+    {
+      /* Let's be liberal for types.  */
+      if (requested_alignment > (max_align = BIGGEST_ALIGNMENT))
+	alignment_too_large_p = true;
+    }
+
+  if (alignment_too_large_p)
+    pedwarn (input_location, OPT_Wattributes,
+	     "requested alignment %d is larger than %d",
+	     requested_alignment, max_align);
+
+  return !alignment_too_large_p;
+}
+
 /* Handle a "aligned" attribute; arguments as in
    struct attribute_spec.handler.  */
 
@@ -7160,7 +7246,8 @@ handle_aligned_attribute (tree *node, tree ARG_UNUSED (name), tree args,
   else if (TYPE_P (*node))
     type = node, is_type = 1;
 
-  if ((i = check_user_alignment (align_expr, false)) == -1)
+  if ((i = check_user_alignment (align_expr, false)) == -1
+      || !check_cxx_fundamental_alignment_constraints (*node, i, flags))
     *no_add_attrs = true;
   else if (is_type)
     {
@@ -7190,6 +7277,17 @@ handle_aligned_attribute (tree *node, tree ARG_UNUSED (name), tree args,
       error ("alignment may not be specified for %q+D", decl);
       *no_add_attrs = true;
     }
+  else if (DECL_USER_ALIGN (decl)
+	   && DECL_ALIGN (decl) > (1U << i) * BITS_PER_UNIT)
+    /* C++-11 [dcl.align/4]:
+
+           When multiple alignment-specifiers are specified for an
+	   entity, the alignment requirement shall be set to the
+	   strictest specified alignment.
+
+      This formally comes from the c++11 specification but we are
+      doing it for the GNU attribute syntax as well.  */
+    *no_add_attrs = true;
   else if (TREE_CODE (decl) == FUNCTION_DECL
 	   && DECL_ALIGN (decl) > (1U << i) * BITS_PER_UNIT)
     {
@@ -11154,4 +11252,22 @@ convert_vector_to_pointer_for_subscript (location_t loc,
     }
 }
 
+/* Return true iff ALIGN is an integral constant that is a fundamental
+   alignment, as defined by [basic.align] in the c++-11
+   specifications.
+
+   That is:
+
+       [A fundamental alignment is represented by an alignment less than or
+        equal to the greatest alignment supported by the implementation
+        in all contexts, which is equal to
+        alignof(max_align_t)].  */
+
+bool
+cxx_fundamental_alignment_p  (unsigned align)
+{
+  return (align <=  MAX (TYPE_ALIGN (long_long_integer_type_node),
+			 TYPE_ALIGN (long_double_type_node)));
+}
+
 #include "gt-c-family-c-common.h"
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index cefe92d..5b23bd3 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -789,6 +789,7 @@ extern bool keyword_begins_type_specifier (enum rid);
 extern bool keyword_is_storage_class_specifier (enum rid);
 extern bool keyword_is_type_qualifier (enum rid);
 extern bool keyword_is_decl_specifier (enum rid);
+extern bool cxx_fundamental_alignment_p (unsigned);
 
 #define c_sizeof(LOC, T)  c_sizeof_or_alignof_type (LOC, T, true, 1)
 #define c_alignof(LOC, T) c_sizeof_or_alignof_type (LOC, T, false, 1)