Patchwork [C++] PR 57211

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Submitter Paolo Carlini
Date May 22, 2013, 1:30 a.m.
Message ID <519C1FBC.6030701@oracle.com>
Download mbox | patch
Permalink /patch/245477/
State New
Headers show

Comments

Paolo Carlini - May 22, 2013, 1:30 a.m.
Hi,

I think submitters have a point that it doesn't make much sense to warn 
about unused parameters of defaulted functions: evidently those exist 
only for documentation purposes. The actual warning is produced by 
do_warn_unused_parameter, which belongs to gcc/function.c, thus the 
simplest solution I have been able to figure out for our front-end issue 
is setting the TREE_NO_WARNING bit, in defaultable_fn_check. I don't 
think we risk suppressing any other warnings.

Tested x86_64-linux.

Thanks,
Paolo.

/////////////////////////
/cp
2013-05-22  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/57211
	* method.c (defaultable_fn_check): Avoid do_warn_unused_parameter
	warnings about defaulted functions.

/testsuite
2013-05-22  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/57211
	* g++.dg/cpp0x/Wunused-parm.C: New.
Jason Merrill - May 22, 2013, 3:18 a.m.
OK.

Jason

Patch

Index: cp/method.c
===================================================================
--- cp/method.c	(revision 199164)
+++ cp/method.c	(working copy)
@@ -1864,13 +1864,19 @@  defaultable_fn_check (tree fn)
     }
   else
     {
-      tree t = FUNCTION_FIRST_USER_PARMTYPE (fn);
-      for (; t && t != void_list_node; t = TREE_CHAIN (t))
+      for (tree t = FUNCTION_FIRST_USER_PARMTYPE (fn);
+	   t && t != void_list_node; t = TREE_CHAIN (t))
 	if (TREE_PURPOSE (t))
 	  {
 	    error ("defaulted function %q+D with default argument", fn);
 	    break;
 	  }
+
+      /* Avoid do_warn_unused_parameter warnings.  */
+      for (tree p = FUNCTION_FIRST_USER_PARM (fn); p; p = DECL_CHAIN (p))
+	if (DECL_NAME (p))
+	  TREE_NO_WARNING (p) = 1;
+
       if (TYPE_BEING_DEFINED (DECL_CONTEXT (fn)))
 	/* Defer checking.  */;
       else if (!processing_template_decl)
Index: testsuite/g++.dg/cpp0x/Wunused-parm.C
===================================================================
--- testsuite/g++.dg/cpp0x/Wunused-parm.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/Wunused-parm.C	(working copy)
@@ -0,0 +1,23 @@ 
+// PR c++/57211
+// { dg-options "-std=c++11 -Wunused-parameter" }
+
+template <class T> T&& move(T&);
+
+struct A
+{
+  struct B
+  {
+    B& operator=(B&&);
+  };
+
+  B f;
+
+  A& operator=(A&& p) = default;
+};
+
+int main()
+{
+  A a;
+  A b;
+  b = move(a);
+}