system.h (TARGET_ESC): Move to ...

	* system.h (TARGET_ESC): Move to ...
	* defaults.h (TARGET_ESC): ... here.
	* target-def.h (TARGET_VALID_DECL_ATTRIBUTE,
	TARGET_VALID_TYPE_ATTRIBUTE): Default to a no-op handler.
	* tree.c (default_valid_attribute_p): New.
	(valid_machine_attribute): Handlers can not be NULL.
	* tree.h (default_valid_attribute_p): New.
	* doc/tm.texi: Document TARGET_ESC.
	* cp/decl2.c (import_export_class): Update.

From-SVN: r43615

gcc/target-def.h

@@ -20,13 +20,16 @@ Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  what you give them.   Help stamp out software-hoarding!  */
 
 /* See target.h for a desciption of what this file contains and how to
-   use it.  */
+   use it.
 
-/* Both in tree.c.  */
+   We want to have non-NULL default definitions of all hook functions,
+   even if they do nothing.  */
+
+/* All in tree.c.  */
 #define TARGET_MERGE_DECL_ATTRIBUTES merge_decl_attributes
 #define TARGET_MERGE_TYPE_ATTRIBUTES merge_type_attributes
-#define TARGET_VALID_DECL_ATTRIBUTE 0
-#define TARGET_VALID_TYPE_ATTRIBUTE 0
+#define TARGET_VALID_DECL_ATTRIBUTE default_valid_attribute_p
+#define TARGET_VALID_TYPE_ATTRIBUTE default_valid_attribute_p
 
 /* The whole shebang.  */
 #define TARGET_INITIALIZER			\

gcc/target.h

@@ -52,13 +52,13 @@ struct gcc_target
   /* Given two types, merge their attributes and return the result.  */
   tree (* merge_type_attributes) PARAMS ((tree, tree));
 
-  /* Nonzero if IDENTIFIER with arguments ARGS is a valid machine
+  /* Return nonzero if IDENTIFIER with arguments ARGS is a valid machine
      specific attribute for DECL.  The attributes in ATTRIBUTES have
      previously been assigned to DECL.  */
   int (* valid_decl_attribute) PARAMS ((tree decl, tree attributes,
 					tree identifier, tree args));
 
-  /* Nonzero if IDENTIFIER with arguments ARGS is a valid machine
+  /* Return nonzero if IDENTIFIER with arguments ARGS is a valid machine
      specific attribute for TYPE.  The attributes in ATTRIBUTES have
      previously been assigned to TYPE.  */
   int (* valid_type_attribute) PARAMS ((tree type, tree attributes,