[PATCH] PR c++/PR48035

[Jason Merrill]

On 03/11/2011 03:01 AM, Jakub Jelinek wrote:
> Do we need to redo parts of class.c anyway?  From what I understand, the
> problematic vtbl pointers are at the end of the base types and DECL_SIZE
> is set to the CLASSTYPE_AS_BASE type size, thus those pointers ought to
> be at or beyond the containing field's size.
> So, can't we simply skip subfields whose bit_position is equal or larger
> to containing field's size?  Something like (works on the testcase from this
> PR, otherwise untested):

Sure, that should work.  I had been thinking of stopping when we run out 
of fields in CLASSTYPE_AS_BASE, but your approach seems simpler.

> Or, in the simplify_aggr_init case where the created tree is handed
> immediately to the gimplifier, there is IMHO no point in initializing
> all fields to zero when the gimplifier throws that immediately away again.

Unfortunately, pointers to data members make this not good enough: 
zero-initializing one means setting the bits to -1.  Though I suppose we 
could keep track of whether or not a class has a pointer to data member 
field somewhere (and therefore need to do this the hard way) and if not, 
just use an empty CONSTRUCTOR.

Jason