Oh, it would be a warning with -Wcast-qual, ok, got it. --David
On Fri, Apr 7, 2017 at 8:21 AM, David Grayson <davidegray...@gmail.com>
wrote:
> > type1 *foo(const type1 *my_const_ptr)
> > {
> > union {
> > type1 *t1;
> > const type1 *ct1;
> > } v;
> > v.ct1 = my_const_ptr;
> > return v.t1;
> > }
>
> Yes, that is sad, and it seems like just a matter of time before a C++
> compiler looks at the code above and reasons that the write to ct1 can be
> optimized away because there is no code that ever reads from ct1. Thus the
> read from t1 will be recognized as undefined behavior (probably called a
> poison value in LLVM) and anything could happen.
>
> What was the problem with Mateusz's patch? I think people are implying it
> results in compiler warnings, but I thought casting a pointer to a pointer
> usually doesn't give any warnings.
>
> --David
>
> On Fri, Apr 7, 2017 at 4:33 AM, Norbert Pfeiler <
> norbert.pfeiler+mingw-...@gmail.com> wrote:
>
>> That’s a kinda sad stance for a compiler support project, don’t you think?
>>
>> Best, Norbert.
>>
>> Liu Hao <lh_mo...@126.com> schrieb am Fr., 7. Apr. 2017 um 05:48 Uhr:
>>
>> > On 2017/4/7 8:11, Norbert Pfeiler wrote:
>> > > Wasn’t LH_Mouse’s point that even if the warning is explicitly turned
>> on
>> > it
>> > > wouldn’t be shown to the user?
>> > >
>> > > The situation for unions is different in C and C++: (I don’t think
>> that
>> > > it’s just about constness changes anything)
>> > > http://stackoverflow.com/questions/11373203
>> > Nice link. Nevertheless, I don't think most people care about UB unless
>> > UB bites them (that is, unless UB refuses to work silently). XD
>> >
>> > --
>> > Best regards,
>> > LH_Mouse
>> >
>> >
>> >
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