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[C++,Patch/RFC] PR 60047

Message ID 52F36B19.9090407@oracle.com
State New
Headers show

Commit Message

Paolo Carlini Feb. 6, 2014, 10:59 a.m. UTC 
Hi,

On 02/05/2014 10:28 PM, Jason Merrill wrote:
> On 02/05/2014 11:19 AM, Paolo Carlini wrote:
>>    if (vec_safe_is_empty (vbases))
>>      /* No virtual bases to worry about.  */;
>>    else if (!assign_p)
>>      {
>>        if (constexpr_p)
>>      *constexpr_p = false;
>
> *constexpr_p should be false for a constructor of a class with virtual 
> bases, according to the standard (7.1.5p4):
>
> The definition of a constexpr constructor shall satisfy the following 
> constraints:
> — the class shall not have any virtual base classes;
> ...
>
> So the assert in implicit_declare_fn is wrong.  I guess I would fix it 
> by checking CLASSTYPE_VBASECLASSES.
Ah! It didn't occur to me that the bug could be in the gcc_assert 
itself. Thus, thanks, I tested on x86_64-linux the below.

Paolo.

//////////////////////
/cp
2014-02-06  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/60047
	* method.c (implicitly_declare_fn): A constructor of a class with
	virtual base classes isn't constexpr (7.1.5p4).
	(synthesized_method_walk): Revert PR58871 change.

/testsuite
2014-02-06  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/60047
	* g++.dg/cpp0x/pr60047.C: New.

Comments

Paolo Carlini Feb. 12, 2014, 7:26 a.m. UTC | #1 
Hi,

the last version of this work is unreviewed, should be rather 
straightforward...

Paolo.
Jason Merrill Feb. 12, 2014, 8:03 a.m. UTC | #2 
On 02/06/2014 02:59 AM, Paolo Carlini wrote:
> -  if (vec_safe_is_empty (vbases))
> +  if (vbases == NULL)

vec_safe_is_empty is still more correct here.

The rest of the patch is OK.

Jason
diff mbox

Patch

Index: cp/method.c
===================================================================
--- cp/method.c	(revision 207536)
+++ cp/method.c	(working copy)
@@ -1366,7 +1366,7 @@  synthesized_method_walk (tree ctype, special_funct
     }
 
   vbases = CLASSTYPE_VBASECLASSES (ctype);
-  if (vec_safe_is_empty (vbases))
+  if (vbases == NULL)
     /* No virtual bases to worry about.  */;
   else if (!assign_p)
     {
@@ -1656,10 +1656,12 @@  implicitly_declare_fn (special_function_kind kind,
   /* Don't bother marking a deleted constructor as constexpr.  */
   if (deleted_p)
     constexpr_p = false;
-  /* A trivial copy/move constructor is also a constexpr constructor.  */
+  /* A trivial copy/move constructor is also a constexpr constructor,
+     unless the class has virtual bases (7.1.5p4).  */
   else if (trivial_p && cxx_dialect >= cxx11
 	   && (kind == sfk_copy_constructor
-	       || kind == sfk_move_constructor))
+	       || kind == sfk_move_constructor)
+	   && !CLASSTYPE_VBASECLASSES (type))
     gcc_assert (constexpr_p);
 
   if (!trivial_p && type_has_trivial_fn (type, kind))
Index: testsuite/g++.dg/cpp0x/pr60047.C
===================================================================
--- testsuite/g++.dg/cpp0x/pr60047.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/pr60047.C	(working copy)
@@ -0,0 +1,14 @@ 
+// PR c++/60047
+// { dg-do compile { target c++11 } }
+
+struct B { };
+
+template<typename T> struct A : virtual B
+{
+  A();
+  A(const A&);
+};
+
+template<typename T> A<T>::A(const A<T>&) = default;
+
+A<int> a = A<int>();