| Message ID | 55BD56D0.601@acm.org |
|---|---|
| State | New |
| Headers | show |
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
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
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() { } +}; +