Some subsurface notes from a week of diving

[Thiago Macieira]

Em seg 17 mar 2014, às 22:26:19, Lubomir I. Ivanov escreveu:
> >         if (!p)
> >                 return -1;
> >         return *p;
> >
> > }
> > 
> > Clang 3.4 removes the check for !p. ICC 14.0 and GCC 4.9 don't.
> 
> quite bogus; i don't see why clang removes the check for !p.

The only way for p to be null is if d was -offsetof(d, p) (that is, -0x4).

The compiler is, in my opinion, quite right to assume that the address of a 
member of an object is not null. A pointer to the top of the object might be, 
but it makes no sense for an object to roll over the top of the memory and 
overflow.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
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