Patchwork [C++] PR 56871

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Submitter Paolo Carlini
Date April 8, 2013, 2:41 p.m.
Message ID <5162D714.3020507@oracle.com>
Download mbox | patch
Permalink /patch/234796/
State New
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Comments

Paolo Carlini - April 8, 2013, 2:41 p.m.
... I think that by the time we do the check, if old_decl is a 
FUNCTION_DECL we can safely assume that new_decl is also a 
FUNCTION_DECL, thus I can simplify the code. I'm finishing testing the 
below variant.

Thanks
Paolo.

///////////////////////
Jason Merrill - April 8, 2013, 5:22 p.m.
OK.

Jason

Patch

Index: cp/decl.c
===================================================================
--- cp/decl.c	(revision 197572)
+++ cp/decl.c	(working copy)
@@ -1196,12 +1196,21 @@  validate_constexpr_redeclaration (tree old_decl, t
   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);
Index: testsuite/g++.dg/cpp0x/constexpr-specialization.C
===================================================================
--- testsuite/g++.dg/cpp0x/constexpr-specialization.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/constexpr-specialization.C	(working copy)
@@ -0,0 +1,12 @@ 
+// 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" }