re PR c++/8057 (Templates/non-templates and warnings about statements without effects)

cp/
	PR c++/8057
	* cvt.c (convert_to_void): Don't warn about unused values when
	processing a template declaration.
testsuite/
	PR c++/8057
	* g++.dg/warn/noeffect7.C: New test.
	* g++.dg/warn/noeffect2.C: Instantiate templates.
	* g++.dg/warn/noeffect4.C: Instantiate template.  Add new error
	and warning.

From-SVN: r105273

gcc/cp/ChangeLog

+2005-10-11  Ian Lance Taylor  <ian@airs.com>
+
+	PR c++/8057
+	* cvt.c (convert_to_void): Don't warn about unused values when
+	processing a template declaration.
+
 2005-10-11  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/21089

gcc/cp/cvt.c

@@ -910,7 +910,10 @@ convert_to_void (tree expr, const char *implicit)
 
   if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
     {
-      if (implicit && warn_unused_value && !TREE_NO_WARNING (expr))
+      if (implicit
+	  && warn_unused_value
+	  && !TREE_NO_WARNING (expr)
+	  && !processing_template_decl)
 	{
 	  /* The middle end does not warn about expressions that have
 	     been explicitly cast to void, so we must do so here.  */

gcc/testsuite/ChangeLog

+2005-10-11  Ian Lance Taylor  <ian@airs.com>
+
+	PR c++/8057
+	* g++.dg/warn/noeffect7.C: New test.
+	* g++.dg/warn/noeffect2.C: Instantiate templates.
+	* g++.dg/warn/noeffect4.C: Instantiate template.  Add new error
+	and warning.
+
 2005-10-11  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/21089

gcc/testsuite/g++.dg/warn/noeffect2.C

@@ -12,7 +12,9 @@ extern "C" void FormatDisk();
   struct C {
     C(){ FormatDisk(), 0; }  // { dg-warning "right-hand operand of comma" "" }
   };
+  template struct C<int>; // { dg-warning "instantiated" }
   template <class T>
   void f() { FormatDisk(), 0; } // { dg-warning "right-hand operand of comma" "" }
+  template void f<int> (); // { dg-warning "instantiated" }
 void g() { FormatDisk(), 0; } // { dg-warning "right-hand operand of comma" "" }
 

gcc/testsuite/g++.dg/warn/noeffect4.C

@@ -76,13 +76,13 @@ template<int I> void Foo (X &x)
   x->m;
   static_cast<int> (x);
   dynamic_cast<Y &> (x);
-  reinterpret_cast<int> (x.Foo ());
-  const_cast<X &> (x.Foo ());
+  reinterpret_cast<int> (x.Foo ()); // { dg-error "invalid cast" }
+  const_cast<X &> (x.Foo ());       // { dg-warning "not used" }
   
   reinterpret_cast<int *> (&x);// { dg-warning "no effect" "" }
   const_cast<X &> (x);         // { dg-warning "no effect" "" }
   sizeof (x++);                // { dg-warning "no effect" "" }
   __alignof__ (x++);           // { dg-warning "no effect" "" }
 }
-  
 
+template void Foo<4> (X&);     // { dg-warning "instantiated" }

gcc/testsuite/g++.dg/warn/noeffect7.C

+// PR c++/8057
+// Don't give a "statement has no effect" warning when declaring a
+// template, only when instantiating it.
+// { dg-do compile }
+// { dg-options "-Wunused" }
+struct Y { static int i; };
+template <typename T> class X { X() { Y::i; }; };
+class Z { Z() { Y::i; }; }; // { dg-warning "no effect" }