re PR c++/92438 (Function declaration parsed incorrectly with `-std=c++1z`)

	PR c++/92438
	* parser.c (cp_parser_constructor_declarator_p): If open paren
	is followed by RID_ATTRIBUTE, skip over the attribute tokens and
	try to parse type specifier.

	* g++.dg/ext/attrib61.C: New test.

From-SVN: r279736

gcc/cp/ChangeLog

+2019-12-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92438
+	* parser.c (cp_parser_constructor_declarator_p): If open paren
+	is followed by RID_ATTRIBUTE, skip over the attribute tokens and
+	try to parse type specifier.
+
 2019-12-23  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR c++/92789

gcc/cp/parser.c

@@ -28493,7 +28493,15 @@ cp_parser_constructor_declarator_p (cp_parser *parser, cp_parser_flags flags,
 	  /* A parameter declaration begins with a decl-specifier,
 	     which is either the "attribute" keyword, a storage class
 	     specifier, or (usually) a type-specifier.  */
-	  && !cp_lexer_next_token_is_decl_specifier_keyword (parser->lexer)
+	  && (!cp_lexer_next_token_is_decl_specifier_keyword (parser->lexer)
+	      /* GNU attributes can actually appear both at the start of
+		 a parameter and parenthesized declarator.
+		 S (__attribute__((unused)) int);
+		 is a constructor, but
+		 S (__attribute__((unused)) foo) (int);
+		 is a function declaration.  */
+	      || (cp_parser_allow_gnu_extensions_p (parser)
+		  && cp_next_tokens_can_be_gnu_attribute_p (parser)))
 	  /* A parameter declaration can also begin with [[attribute]].  */
 	  && !cp_next_tokens_can_be_std_attribute_p (parser))
 	{
@@ -28501,6 +28509,13 @@ cp_parser_constructor_declarator_p (cp_parser *parser, cp_parser_flags flags,
 	  tree pushed_scope = NULL_TREE;
 	  unsigned saved_num_template_parameter_lists;
 
+	  if (cp_next_tokens_can_be_gnu_attribute_p (parser))
+	    {
+	      unsigned int n = cp_parser_skip_gnu_attributes_opt (parser, 1);
+	      while (--n)
+		cp_lexer_consume_token (parser->lexer);
+	    }
+
 	  /* Names appearing in the type-specifier should be looked up
 	     in the scope of the class.  */
 	  if (current_class_type)

gcc/testsuite/ChangeLog

+2019-12-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92438
+	* g++.dg/ext/attrib61.C: New test.
+
 2019-12-23  Thomas Schwinge  <thomas@codesourcery.com>
 
 	* c-c++-common/goacc/mdc-1.c: Restrict to LP64, LLP64.

gcc/testsuite/g++.dg/ext/attrib61.C

+// PR c++/92438
+// { dg-do compile }
+
+typedef struct S { int x; } T;
+T (foo) (T x);
+T __attribute__((unused)) bar (T x);
+struct S (__attribute__((unused)) baz) (T x);
+T (__attribute__((unused)) qux) (T x);
+
+struct U
+{
+  U (__attribute__((unused)) int);
+  U (__attribute__((unused)) corge) (int);
+};
+
+void
+test ()
+{
+  T a, b;
+  a = foo (b);
+  b = bar (a);
+  a = baz (b);
+  b = qux (a);
+  U u (5);
+  U v = u.corge (3);
+}