re PR c++/56871 ([c++11] Specialization of constexpr Templated Function)

/cp
2013-04-08  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/56871
	* decl.c (validate_constexpr_redeclaration): Allow an explicit
	specialization to be different wrt the constexpr specifier.

/testsuite
2013-04-08  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/56871
	* g++.dg/cpp0x/constexpr-specialization.C: New.

From-SVN: r197597

gcc/cp/ChangeLog

+2013-04-08  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/56871
+	* decl.c (validate_constexpr_redeclaration): Allow an explicit
+	specialization to be different wrt the constexpr specifier.
+
 2013-04-06  Jason Merrill  <jason@redhat.com>
 
 	* parser.c (cp_parser_std_attribute): Treat [[noreturn]] like GNU

gcc/cp/decl.c

@@ -1196,12 +1196,21 @@ validate_constexpr_redeclaration (tree old_decl, tree new_decl)
   if (DECL_DECLARED_CONSTEXPR_P (old_decl)
       == DECL_DECLARED_CONSTEXPR_P (new_decl))
     return true;
-  if (TREE_CODE (old_decl) == FUNCTION_DECL && DECL_BUILT_IN (old_decl))
+  if (TREE_CODE (old_decl) == FUNCTION_DECL)
     {
-      /* Hide a built-in declaration.  */
-      DECL_DECLARED_CONSTEXPR_P (old_decl)
-	= DECL_DECLARED_CONSTEXPR_P (new_decl);
-      return true;
+      if (DECL_BUILT_IN (old_decl))
+	{
+	  /* Hide a built-in declaration.  */
+	  DECL_DECLARED_CONSTEXPR_P (old_decl)
+	    = DECL_DECLARED_CONSTEXPR_P (new_decl);
+	  return true;
+	}
+      /* 7.1.5 [dcl.constexpr]
+	 Note: An explicit specialization can differ from the template
+	 declaration with respect to the constexpr specifier.  */
+      if (! DECL_TEMPLATE_SPECIALIZATION (old_decl)
+	  && DECL_TEMPLATE_SPECIALIZATION (new_decl))
+	return true;
     }
   error ("redeclaration %qD differs in %<constexpr%>", new_decl);
   error ("from previous declaration %q+D", old_decl);

gcc/testsuite/ChangeLog

+2013-04-08  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/56871
+	* g++.dg/cpp0x/constexpr-specialization.C: New.
+
 2013-04-08  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.c-torture/execute/pr56837.c: New test.

gcc/testsuite/g++.dg/cpp0x/constexpr-specialization.C

+// PR c++/56871
+// { dg-options "-std=c++11" }
+
+template<typename T> constexpr int foo(T);
+template<> int foo(int);
+template<> int foo(int);            // { dg-error "previous" }
+template<> constexpr int foo(int);  // { dg-error "redeclaration" }
+
+template<typename T> int bar(T);
+template<> constexpr int bar(int);
+template<> constexpr int bar(int);  // { dg-error "previous" }
+template<> int bar(int);            // { dg-error "redeclaration" }