GCC screws up pointer->ulong conversion on 32 bit systems

[Iain Buclaw]

On Saturday, 9 November 2013 at 17:53:41 UTC, Johannes Pfau wrote:
> Am Sat, 9 Nov 2013 17:01:43 +0000
> schrieb Iain Buclaw <ibuclaw at ubuntu.com>:
>
>> On 9 November 2013 12:19, Johannes Pfau <nospam at example.com> 
>> wrote:
>> > The fix is simple:
>> > in gcc/convert.c(convert_to_integer):
>> >
>> > /* Convert to an unsigned integer of the correct width 
>> > first, and
>> > from there widen/truncate to the required type.  Some targets
>> > support the coexistence of multiple valid pointer sizes, so 
>> > fetch
>> > the one we need from the type.  */
>> >       expr = fold_build1 (CONVERT_EXPR,
>> >                           lang_hooks.types.type_for_size
>> >                             (TYPE_PRECISION (intype), 0),
>> >                           expr);
>> >
>> >
>> That code does seem to contradict what the comment is saying.  
>> I'll
>> raise it in #gcc and send a patch  (unless you want to do it).
>> 
>> 
>
> It indeed seems like it's only a small oversight. It'd be
> great if you could report it.

Apparently it's working as per C semantics, which means the 
behavior is undefined.  I've mentioned that it makes no sense 
that documentation/code don't match comments. But all I've heard 
back is that you shouldn't use convert_to_integer in the front 
end (except maybe through convert() - which I am 90% certain is 
the case with us), and to implement our own semantics if we say 
that pointer to integer conversion is clearly defined in D.

Regards
Iain.