Patchwork C++ PATCH for c++/54277 (wrong cv-quals in lambda)

On 03/16/2013 03:28 PM, Jason Merrill wrote:
> I have no idea why the existing code tried to deduce the desired quals
> from current_class_ref rather than just look at the object it has.

Well, maybe now I do; when I tested all my changes again before checking 
in, this one caused a crash because I had left out another change that 
it depends on.  Previously we gave the 'this' capture in a lambda a 
DECLTYPE_TYPE type since the enclosing class is a dependent type, but 
that means that *this has no type at all and so we can't look at its 
quals.  But that isn't necessary; we know enough about the type of 
'this' that it's a pointer to some instantiation of this class template, 
so we can give the capture field and proxy that type rather than mess 
with DECLTYPE_TYPE.  We could limit this change to only POINTER_TYPE, 
but we might as well save a bit of memory and only use the DECLTYPE_TYPE 
when we really don't know anything about the type being captured; 
specifically, when we don't know whether or not it's a reference.

Tested x86_64-pc-linux-gnu, applying to trunk.

On 13-03-16 10:40 PM, Jason Merrill wrote:
> On 03/16/2013 03:28 PM, Jason Merrill wrote:
>> I have no idea why the existing code tried to deduce the desired quals
>> from current_class_ref rather than just look at the object it has.
>
> Well, maybe now I do; when I tested all my changes again before checking
> in, this one caused a crash because I had left out another change that
> it depends on.  Previously we gave the 'this' capture in a lambda a
> DECLTYPE_TYPE type since the enclosing class is a dependent type, but
> that means that *this has no type at all and so we can't look at its
> quals.  But that isn't necessary; we know enough about the type of
> 'this' that it's a pointer to some instantiation of this class template,
> so we can give the capture field and proxy that type rather than mess
> with DECLTYPE_TYPE.  We could limit this change to only POINTER_TYPE,
> but we might as well save a bit of memory and only use the DECLTYPE_TYPE
> when we really don't know anything about the type being captured;
> specifically, when we don't know whether or not it's a reference.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.

Hi Jason,

It seems this change introduced the following segfault building 
compatibility-thread-c++0x.cc for an arm eabi target.

ice.ii:48:20: internal compiler error: Segmentation fault
         (__args) ...);
                     ^
0xa7b67f crash_signal
	../../gcc/toplev.c:332
0x4e98e2 resolve_args
	../../gcc/cp/call.c:3739
0x5022d7 build_new_function_call(tree_node*, vec<tree_node*, va_gc, 
vl_embed>**, bool, int)
	../../gcc/cp/call.c:3849
0x66dc42 finish_call_expr(tree_node*, vec<tree_node*, va_gc, 
vl_embed>**, bool, bool, int)
	../../gcc/cp/semantics.c:2214

Attached is a reduced testcase. Sorry, for reporting it on gcc-patches 
but bugzilla is currently offline.

Regards,

Ryan Mansfield
namespace std __attribute__ ((__visibility__ ("default")))
{
  template < typename _Tp > struct remove_reference
  {
    typedef _Tp type;
  };
  template < typename _Tp > constexpr _Tp
    && forward (typename std::remove_reference < _Tp >::type & __t) noexcept
  {
    return static_cast < _Tp && >(__t);
  }
  template < typename _Res, typename _T1,
    typename _T2 >
    struct _Reference_wrapper_base <_Res (_T1::*) (_T2) const volatile
    >:binary_function < const volatile _T1 *, _T2, _Res >
  {
  };
template < typename _Tp > class reference_wrapper:public _Reference_wrapper_base < typename remove_cv <
    _Tp >::type >
  {
  };
  template < typename _Tp > inline reference_wrapper < _Tp >
    ref (_Tp & __t) noexcept
  {
  }
  template < typename _Signature > struct _Bind_simple;
  template < typename _Func, typename ... _BoundArgs > struct _Bind_simple_helper
  {
    typedef _Bind_simple < __func_type (typename decay <
					_BoundArgs >::type ...) > __type;
  };
  template < typename _Callable,
    typename ... _Args > typename _Bind_simple_helper < _Callable,
    _Args ... >::__type __bind_simple (_Callable && __callable, _Args
				       && ... __args)
  {
  }
  template < typename _Signature > class function;
  struct once_flag
  {
  };
  template < typename _Callable,
    typename ... _Args > void call_once (once_flag & __once, _Callable
					 && __f, _Args && ... __args)
  {
    auto __callable = std::__bind_simple (std::forward < _Callable > (__f),
					  std::forward < _Args >
					  (__args) ...);
    __once_functor =[&]()
    {
      __callable ();
    };
  }
  class _State_base
  {
    once_flag _M_once;
    void _M_set_result (function < _Ptr_type () > __res,
			bool __ignore_failure = false)
    {
      bool __set = __ignore_failure;
        call_once (_M_once, &_State_base::_M_do_set, this, ref (__res),
		   ref (__set));
    }
  private:void _M_do_set (function < _Ptr_type () > &__f, bool & __set)
    {

    }
  }
}