[Bug c++/50282] pointer-to-member cast works incorrectly

["imzhuli at vip dot qq.com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50282

--- Comment #4 from zhuli <imzhuli at vip dot qq.com> 2011-09-03 12:17:35 UTC ---
yes, you are right. 
As an addition, compiling with -O2 might yield an warning, as you metioned.

but i checked my env(32-bit) and used default compiler option, so i just simply
assumed 4byte-object & 16byte-object share the same alignment. and as this is
not the point of the issue, i didnt take much care about that. In fact, i
seldom use such code, even to debug.
Anyway, you comment is advisable, thanks.



(In reply to comment #3)
> (In reply to comment #2)
> > I've never used any unint32_t tu hold any pointer-to-member, 
> > I just tested and find out the sizeof (pointer-to-member-function) is 16, 
> > then i used a pointer-to-uint32_t four times to dump the value of the
> > pointer-to-member, 32bits by 32bits.
> >
> > According my understanding to the standard, this conversion should be valid, or
> > there must be any valid way . 
> 
> The above violates C++ aliasing rules but would be supported by GCC as an
> extension with -O[01] or -fno-strict-aliasing.  The standard only allows
> accessing the storage via a character type (thus, dump 16 individual bytes via
> a char * pointer).
> 
> > (In reply to comment #1)
> > > uint32_t isn't big enough to hold a pointer-to-member value, and that
> > > conversion isn't valid anyway