On Wed, 28 Jun 2017, Dmitry Vyukov wrote:
> On Wed, Jun 28, 2017 at 1:10 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> >> In my case I ended up with something like:
> >>
> >> __typeof__(foo) __ptr = __ptr;
> >>
> >> which compiler decided to turn into 0.
> >>
> >> Thank you, macros.
> >>
> >> We can add more underscores, but the problem can happen again. Should
> >> we prefix current function/macro name to all local vars?..
> >
> > Actually we can void that ___ptr dance completely.
> >
> > Thanks,
> >
> > tglx
> >
> > 8<--------------------
> >
> > --- a/include/asm-generic/atomic-instrumented.h
> > +++ b/include/asm-generic/atomic-instrumented.h
> > @@ -359,37 +359,32 @@ static __always_inline bool atomic64_add
> >
> > #define cmpxchg(ptr, old, new) \
> > ({ \
> > - __typeof__(ptr) ___ptr = (ptr); \
> > - kasan_check_write(___ptr, sizeof(*___ptr)); \
> > + kasan_check_write((ptr), sizeof(*(ptr))); \
> > arch_cmpxchg((ptr), (old), (new)); \
> > })
> >
> > #define sync_cmpxchg(ptr, old, new) \
> > ({ \
> > - __typeof__(ptr) ___ptr = (ptr); \
> > - kasan_check_write(___ptr, sizeof(*___ptr)); \
> > - arch_sync_cmpxchg(___ptr, (old), (new)); \
> > + kasan_check_write((ptr), sizeof(*(ptr))); \
> > + arch_sync_cmpxchg((ptr), (old), (new)); \
> > })
> >
> > #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.
Sigh, is that actually used?
That's all insane. The whole crap gets worse because:
cmpxchg() can be used on u8, u16, u32 ....
There is a reason why type safety matters.
Thanks,
tglx
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