On Wed, 28 Jun 2017, Dmitry Vyukov wrote:
> On Wed, Jun 28, 2017 at 2:24 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > On Wed, 28 Jun 2017, Dmitry Vyukov wrote:
> >> On Wed, Jun 28, 2017 at 1:10 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> >> > #define cmpxchg_local(ptr, old, new) \
> >> > ({ \
> >> > - __typeof__(ptr) ____ptr = (ptr); \
> >> > - kasan_check_write(____ptr, sizeof(*____ptr)); \
> >> > - arch_cmpxchg_local(____ptr, (old), (new)); \
> >> > + kasan_check_write((ptr), sizeof(*(ptr))); \
> >> > + arch_cmpxchg_local((ptr), (old), (new)); \
> >>
> >>
> >> /\/\/\/\/\/\/\/\/\/\/\/\
> >>
> >> These are macros.
> >> If ptr is foo(), then we will call foo() twice.
> >
> > If that's true, the foo() will be evaluated a gazillion more times down the
> > way to the end of this macro maze.
>
> No. If we do:
>
> __typeof__(ptr) ____ptr = (ptr);
>
> and then only use ____ptr, then ptr is evaluated only once regardless
> of what the rest of macros do.
What I meant is, that we have today nested macros which do a lot of that
same nonsense even w/o that patch.
Thanks,
tglx
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