c-family: Allow placement of attributes on function definitions.

This is to address Issue gcc-mirror#12.

It is very unlikely to be acceptable upstream, because the situation
with how GNU attributes appertain is already very complex.  This is
strictly an extension to allow us to consume them in the same position
as clang does.

gcc/c-family/ChangeLog:

	* c.opt:

gcc/c/ChangeLog:

	* c-parser.cc (c_parser_declaration_or_fndef):

gcc/ChangeLog:

	* config/darwin.cc (darwin_override_options):

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_init_declarator):

Signed-off-by: Iain Sandoe <[email protected]>

Author: iains

gcc/c-family/c.opt

@@ -1805,6 +1805,10 @@ static-libmpxwrappers
 Driver WarnRemoved
 Removed in GCC 9.  This switch has no effect.
 
+fallow-extended-attribute-placement
+C ObjC C++ ObjC++ LTO Var(flag_allow_ext_attr_placement) Init(0)
+Allow placement of attributes on function definitions.
+
 fcilkplus
 C ObjC C++ ObjC++ LTO Undocumented Ignore
 Removed in GCC 8.  This switch has no effect.

gcc/c/c-parser.cc

@@ -2691,15 +2691,28 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
 	    d = d->declarator;
 	  underspec_name = d->u.id.id;
 	}
+      tree postfix_attrs = NULL_TREE;
+      if (flag_allow_ext_attr_placement
+	  && c_parser_next_token_is_keyword (parser, RID_ATTRIBUTE))
+	{
+	  postfix_attrs = c_parser_gnu_attributes (parser);
+	  /* IF we have a function definition, and we're allowing it then
+	     treat these attributes as if they had been prepended.  */
+	  if (c_parser_next_token_is (parser, CPP_OPEN_BRACE))
+	    {
+	      all_prefix_attrs = chainon (all_prefix_attrs, postfix_attrs);
+	      postfix_attrs = NULL_TREE;
+	    }
+	}
       if (c_parser_next_token_is (parser, CPP_EQ)
 	  || c_parser_next_token_is (parser, CPP_COMMA)
 	  || c_parser_next_token_is (parser, CPP_SEMICOLON)
 	  || c_parser_next_token_is_keyword (parser, RID_ASM)
 	  || c_parser_next_token_is_keyword (parser, RID_ATTRIBUTE)
+	  || postfix_attrs
 	  || c_parser_next_token_is_keyword (parser, RID_IN))
 	{
 	  tree asm_name = NULL_TREE;
-	  tree postfix_attrs = NULL_TREE;
 	  if (!diagnosed_no_specs && !specs->declspecs_seen_p)
 	    {
 	      diagnosed_no_specs = true;
@@ -2711,8 +2724,9 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
 	  if (c_parser_next_token_is_keyword (parser, RID_ASM))
 	    asm_name = c_parser_simple_asm_expr (parser);
 	  if (c_parser_next_token_is_keyword (parser, RID_ATTRIBUTE))
+	    postfix_attrs = c_parser_gnu_attributes (parser);
+	  if (postfix_attrs)
 	    {
-	      postfix_attrs = c_parser_gnu_attributes (parser);
 	      if (c_parser_next_token_is (parser, CPP_OPEN_BRACE))
 		{
 		  /* This means there is an attribute specifier after

gcc/config/darwin.cc

@@ -3592,6 +3592,11 @@ darwin_override_options (void)
 
   /* The c_dialect...() macros are not available to us here.  */
   darwin_running_cxx = (strstr (lang_hooks.name, "C++") != 0);
+
+  /* We need to consume attributes on function definitions from the the SDK
+     headers.  */
+  if (!OPTION_SET_P (flag_allow_ext_attr_placement))
+    flag_allow_ext_attr_placement = true;
 }
 
 #if DARWIN_PPC

gcc/cp/parser.cc

@@ -23966,9 +23966,16 @@ cp_parser_init_declarator (cp_parser* parser,
 		      "an %<asm%> specification is not allowed "
 		      "on a function-definition");
 	  if (attributes)
-	    error_at (attributes_start_token->location,
-		      "attributes are not allowed "
-		      "on a function-definition");
+	    {
+	      /* When we are allowing attributes in this position, then add
+		 them to the prefix ones.  */
+	      if (flag_allow_ext_attr_placement)
+		prefix_attributes = chainon (prefix_attributes, attributes);
+	      else
+		error_at (attributes_start_token->location,
+			  "attributes are not allowed "
+			  "on a function-definition");
+	    }
 	  /* This is a function-definition.  */
 	  *function_definition_p = true;