* [C++/66443]
@ 2015-06-30 0:10 Nathan Sidwell
2015-06-30 4:24 ` [C++/66443] Jason Merrill
0 siblings, 1 reply; 9+ messages in thread
From: Nathan Sidwell @ 2015-06-30 0:10 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
[-- Attachment #1: Type: text/plain, Size: 580 bytes --]
This patch fixes 66443, a defect introduced by a C++14 change concerning virtual
bases of abstract classes.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66443 points at DR1611 & 1658,
which describe the issue. Essentially, an abstract class type can only exist as
a base of some other (non-abstract) class. Any virtual bases of the abstract
class will be constructed by the containing class itself. In this specific
instance, a deleted default ctor of such a virtual base should not delete the
abstract class's default dtor.
built & tested on x6-64-linux, ok?
nathan
[-- Attachment #2: 66443.patch --]
[-- Type: text/x-patch, Size: 2259 bytes --]
2015-06-29 Nathan Sidwell <nathan@acm.org>
PR c++/66443
* init.c (emit_mem_initializers): Do not emit initializers for
virtual bases of abstract classes.
* method.c (synthesized_method_walk): Skip virtual bases of
abstract classes in C++14 mode.
PR c++/66443
* cpp1y/pr66443.C: New test.
Index: cp/init.c
===================================================================
--- cp/init.c (revision 225103)
+++ cp/init.c (working copy)
@@ -1139,9 +1139,7 @@ emit_mem_initializers (tree mem_inits)
}
/* Initialize the base. */
- if (BINFO_VIRTUAL_P (subobject))
- construct_virtual_base (subobject, arguments);
- else
+ if (!BINFO_VIRTUAL_P (subobject))
{
tree base_addr;
@@ -1155,6 +1153,8 @@ emit_mem_initializers (tree mem_inits)
tf_warning_or_error);
expand_cleanup_for_base (subobject, NULL_TREE);
}
+ else if (!ABSTRACT_CLASS_TYPE_P (current_class_type))
+ construct_virtual_base (subobject, arguments);
}
in_base_initializer = 0;
Index: cp/method.c
===================================================================
--- cp/method.c (revision 225103)
+++ cp/method.c (working copy)
@@ -1505,7 +1505,10 @@ synthesized_method_walk (tree ctype, spe
vbases = CLASSTYPE_VBASECLASSES (ctype);
if (vec_safe_is_empty (vbases))
/* No virtual bases to worry about. */;
- else if (!assign_p)
+ else if (!assign_p
+ /* C++14 ignores virtual bases of abstract classes, as they
+ can never be directly called. */
+ && (cxx_dialect < cxx14 || !ABSTRACT_CLASS_TYPE_P (ctype)))
{
if (constexpr_p)
*constexpr_p = false;
Index: testsuite/g++.dg/cpp1y/pr66443.C
===================================================================
--- testsuite/g++.dg/cpp1y/pr66443.C (revision 0)
+++ testsuite/g++.dg/cpp1y/pr66443.C (working copy)
@@ -0,0 +1,22 @@
+// PR c++/66443
+// { dg-do compile { target c++14 } }
+
+class A {
+public:
+ A( int ) { }
+};
+
+// B's virtual base is ignored for default ctor determination as B is
+// abstract. DR1611 & DR1658
+
+class B: virtual public A {
+public:
+ virtual void do_something() = 0;
+};
+
+class C: public B {
+public:
+ C(): A( 1 ) { }
+ virtual void do_something() { }
+};
+
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443]
2015-06-30 0:10 [C++/66443] Nathan Sidwell
@ 2015-06-30 4:24 ` Jason Merrill
2015-06-30 23:24 ` [C++/66443] Nathan Sidwell
0 siblings, 1 reply; 9+ messages in thread
From: Jason Merrill @ 2015-06-30 4:24 UTC (permalink / raw)
To: Nathan Sidwell, GCC Patches
On 06/29/2015 06:57 PM, Nathan Sidwell wrote:
> * method.c (synthesized_method_walk): Skip virtual bases of
> abstract classes in C++14 mode.
Let's not limit this to C++14 mode; most DRs apply to earlier standards
as well.
Jason
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443]
2015-06-30 4:24 ` [C++/66443] Jason Merrill
@ 2015-06-30 23:24 ` Nathan Sidwell
2015-07-08 14:50 ` [C++/66443] virtual base of abstract class Nathan Sidwell
0 siblings, 1 reply; 9+ messages in thread
From: Nathan Sidwell @ 2015-06-30 23:24 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
On 06/30/15 00:19, Jason Merrill wrote:
> On 06/29/2015 06:57 PM, Nathan Sidwell wrote:
>> * method.c (synthesized_method_walk): Skip virtual bases of
>> abstract classes in C++14 mode.
>
> Let's not limit this to C++14 mode; most DRs apply to earlier standards as well.
ok, works for me.
(sorry for failing to complete the subject line.)
nathan
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443] virtual base of abstract class
2015-06-30 23:24 ` [C++/66443] Nathan Sidwell
@ 2015-07-08 14:50 ` Nathan Sidwell
2015-07-17 19:57 ` Jason Merrill
0 siblings, 1 reply; 9+ messages in thread
From: Nathan Sidwell @ 2015-07-08 14:50 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
On 06/30/15 19:21, Nathan Sidwell wrote:
> On 06/30/15 00:19, Jason Merrill wrote:
>> On 06/29/2015 06:57 PM, Nathan Sidwell wrote:
>>> * method.c (synthesized_method_walk): Skip virtual bases of
>>> abstract classes in C++14 mode.
>>
>> Let's not limit this to C++14 mode; most DRs apply to earlier standards as well.
curiously opening it up leads to some test failures related to determining the
exception specifier for implicit ctors and dtors. Not had time to investigate
that yet ...
nathan
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443] virtual base of abstract class
2015-07-08 14:50 ` [C++/66443] virtual base of abstract class Nathan Sidwell
@ 2015-07-17 19:57 ` Jason Merrill
2015-07-17 20:12 ` Nathan Sidwell
0 siblings, 1 reply; 9+ messages in thread
From: Jason Merrill @ 2015-07-17 19:57 UTC (permalink / raw)
To: Nathan Sidwell, GCC Patches
On 07/08/2015 10:50 AM, Nathan Sidwell wrote:
> On 06/30/15 19:21, Nathan Sidwell wrote:
>> On 06/30/15 00:19, Jason Merrill wrote:
>>> On 06/29/2015 06:57 PM, Nathan Sidwell wrote:
>>>> * method.c (synthesized_method_walk): Skip virtual bases of
>>>> abstract classes in C++14 mode.
>>>
>>> Let's not limit this to C++14 mode; most DRs apply to earlier
>>> standards as well.
>
> curiously opening it up leads to some test failures related to
> determining the exception specifier for implicit ctors and dtors. Not
> had time to investigate that yet ...
If C++98 mode is problematic, we can limit this to C++11 and up.
Jason
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443] virtual base of abstract class
2015-07-17 19:57 ` Jason Merrill
@ 2015-07-17 20:12 ` Nathan Sidwell
2015-08-01 23:31 ` Nathan Sidwell
0 siblings, 1 reply; 9+ messages in thread
From: Nathan Sidwell @ 2015-07-17 20:12 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
On 07/17/15 15:42, Jason Merrill wrote:
> On 07/08/2015 10:50 AM, Nathan Sidwell wrote:
>> On 06/30/15 19:21, Nathan Sidwell wrote:
>>> On 06/30/15 00:19, Jason Merrill wrote:
>>>> On 06/29/2015 06:57 PM, Nathan Sidwell wrote:
>>>>> * method.c (synthesized_method_walk): Skip virtual bases of
>>>>> abstract classes in C++14 mode.
>>>>
>>>> Let's not limit this to C++14 mode; most DRs apply to earlier
>>>> standards as well.
>>
>> curiously opening it up leads to some test failures related to
>> determining the exception specifier for implicit ctors and dtors. Not
>> had time to investigate that yet ...
>
> If C++98 mode is problematic, we can limit this to C++11 and up.
I'm not yet sure. The failure mode I saw surprised me, and suggests there's
something wrong with the patch. Sadly, I've got interrupted by other stuff.
nathan
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443] virtual base of abstract class
2015-07-17 20:12 ` Nathan Sidwell
@ 2015-08-01 23:31 ` Nathan Sidwell
2015-08-03 3:44 ` Jason Merrill
0 siblings, 1 reply; 9+ messages in thread
From: Nathan Sidwell @ 2015-08-01 23:31 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
[-- Attachment #1: Type: text/plain, Size: 1775 bytes --]
On 07/17/15 15:59, Nathan Sidwell wrote:
> On 07/17/15 15:42, Jason Merrill wrote:
>> On 07/08/2015 10:50 AM, Nathan Sidwell wrote:
>>> On 06/30/15 19:21, Nathan Sidwell wrote:
>>>> On 06/30/15 00:19, Jason Merrill wrote:
>>>>> On 06/29/2015 06:57 PM, Nathan Sidwell wrote:
>>>>>> * method.c (synthesized_method_walk): Skip virtual bases of
>>>>>> abstract classes in C++14 mode.
>>>>>
>>>>> Let's not limit this to C++14 mode; most DRs apply to earlier
>>>>> standards as well.
>>>
>>> curiously opening it up leads to some test failures related to
>>> determining the exception specifier for implicit ctors and dtors. Not
>>> had time to investigate that yet ...
>>
>> If C++98 mode is problematic, we can limit this to C++11 and up.
>
> I'm not yet sure. The failure mode I saw surprised me, and suggests there's
> something wrong with the patch. Sadly, I've got interrupted by other stuff.
Ok, this patch fixes things up. The previous version was a little too lax,
extending the logic of DR1611 to all synthesized functions. However, this broke
virtual synthesized dtors, in that an abstract class's synthesized dtor's
exception specification would not take account of any virtual base dtor
exception specs. This would mean that a non-abstract derived class's
synthesized dtor might end up with a throwing exception spec (because the
virtual base's dtor did), and that would be looser than the exception spec on
the abstract base's non-callable synthesized dtor. And that fails the virtual
overriding checks.
So this restricts the skipping to exactly what DR 1611 discusses -- default
constructors of virtual bases of an abstract class. Those can never be virtual,
so we don't end up with the above problem in that case.
Jason, WDYT?
nathan
[-- Attachment #2: 66443-2.patch --]
[-- Type: text/x-patch, Size: 2403 bytes --]
2015-08-01 Nathan Sidwell <nathan@acm.org>
cp/
PR c++/66443
* init.c (emit_mem_initializers): Do not emit initializers for
virtual bases of abstract classes.
* method.c (synthesized_method_walk): Skip virtual bases of
abstract classes in C++14 mode.
testsuite/
PR c++/66443
* cpp1y/pr66443.C: New test.
Index: cp/init.c
===================================================================
--- cp/init.c (revision 226444)
+++ cp/init.c (working copy)
@@ -1140,9 +1140,7 @@ emit_mem_initializers (tree mem_inits)
}
/* Initialize the base. */
- if (BINFO_VIRTUAL_P (subobject))
- construct_virtual_base (subobject, arguments);
- else
+ if (!BINFO_VIRTUAL_P (subobject))
{
tree base_addr;
@@ -1156,6 +1154,8 @@ emit_mem_initializers (tree mem_inits)
tf_warning_or_error);
expand_cleanup_for_base (subobject, NULL_TREE);
}
+ else if (!ABSTRACT_CLASS_TYPE_P (current_class_type))
+ construct_virtual_base (subobject, arguments);
}
in_base_initializer = 0;
Index: cp/method.c
===================================================================
--- cp/method.c (revision 226444)
+++ cp/method.c (working copy)
@@ -1506,7 +1506,13 @@ synthesized_method_walk (tree ctype, spe
vbases = CLASSTYPE_VBASECLASSES (ctype);
if (vec_safe_is_empty (vbases))
/* No virtual bases to worry about. */;
- else if (!assign_p)
+ else if (!assign_p
+ /* DR 1611 ignores virtual bases of abstract classes for
+ the default constructor. Such ctors can never be
+ directly called. Thus their deletion should not affect
+ whether they are deleted in this class. */
+ && (!ABSTRACT_CLASS_TYPE_P (ctype) || sfk != sfk_constructor
+ || inherited_parms))
{
if (constexpr_p)
*constexpr_p = false;
Index: testsuite/g++.dg/other/pr66443.C
===================================================================
--- testsuite/g++.dg/other/pr66443.C (revision 0)
+++ testsuite/g++.dg/other/pr66443.C (working copy)
@@ -0,0 +1,21 @@
+// { dg-do compile }
+
+class A {
+public:
+ A( int ) { }
+};
+
+// B's virtual base is ignored for default ctor determination as B is
+// abstract. DR1611 & DR1658
+
+class B: virtual public A {
+public:
+ virtual void do_something() = 0;
+};
+
+class C: public B {
+public:
+ C(): A( 1 ) { }
+ virtual void do_something() { }
+};
+
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443] virtual base of abstract class
2015-08-01 23:31 ` Nathan Sidwell
@ 2015-08-03 3:44 ` Jason Merrill
2015-08-03 13:20 ` Nathan Sidwell
0 siblings, 1 reply; 9+ messages in thread
From: Jason Merrill @ 2015-08-03 3:44 UTC (permalink / raw)
To: Nathan Sidwell, GCC Patches
On 08/01/2015 07:31 PM, Nathan Sidwell wrote:
> Ok, this patch fixes things up. The previous version was a little too
> lax, extending the logic of DR1611 to all synthesized functions.
> However, this broke virtual synthesized dtors, in that an abstract
> class's synthesized dtor's exception specification would not take
> account of any virtual base dtor exception specs. This would mean that
> a non-abstract derived class's synthesized dtor might end up with a
> throwing exception spec (because the virtual base's dtor did), and that
> would be looser than the exception spec on the abstract base's
> non-callable synthesized dtor. And that fails the virtual overriding
> checks.
It seems to me that DR 1658 ignores vbases of abstract classes for
determining whether a destructor is deleted, but says nothing about
exception specifications.
DR 1351 specifically ignores vbases of abstract classes for determining
the exception specification of a constructor, but only for constructors.
So I think that for destructors we want to walk the base, but pass in a
fake delete_p.
Why the check for inherited_parms? I would think that inheriting
constructors would be handled like other ctors.
Jason
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [C++/66443] virtual base of abstract class
2015-08-03 3:44 ` Jason Merrill
@ 2015-08-03 13:20 ` Nathan Sidwell
0 siblings, 0 replies; 9+ messages in thread
From: Nathan Sidwell @ 2015-08-03 13:20 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
On 08/02/15 23:44, Jason Merrill wrote:
> It seems to me that DR 1658 ignores vbases of abstract classes for determining
> whether a destructor is deleted, but says nothing about exception specifications.
>
> DR 1351 specifically ignores vbases of abstract classes for determining the
> exception specification of a constructor, but only for constructors.
>
> So I think that for destructors we want to walk the base, but pass in a fake
> delete_p.
Ok. that all makes sense.
> Why the check for inherited_parms? I would think that inheriting constructors
> would be handled like other ctors.
I think I continue to be confused ...
nathan
^ permalink raw reply [flat|nested] 9+ messages in thread
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2015-06-30 4:24 ` [C++/66443] Jason Merrill
2015-06-30 23:24 ` [C++/66443] Nathan Sidwell
2015-07-08 14:50 ` [C++/66443] virtual base of abstract class Nathan Sidwell
2015-07-17 19:57 ` Jason Merrill
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