[PATCH v4 04/21] nptl: x32: Fix Race conditions in pthread cancellation [BZ#12683]

[Adhemerval Zanella]

On 03/04/2020 18:22, Joseph Myers wrote:
> On Fri, 3 Apr 2020, Adhemerval Zanella via Libc-alpha wrote:
> 
>> This patches adds the x32 modification required for the BZ#12683.
>> It follows the x86_64-x32 ABI and pointers are zero-extended.
>> However, compiler may not see such cases and accuse a cast from pointer
>> to integer of different size and for such cases the warning is
>> explict disabled.
> 
> MIPS n32 uses an intermediate cast to (__typeof__ ((X) - (X))), so that a 
> conversion to a different size is never directly from a pointer type.  
> Does something like that help here to avoid the warning without needing to 
> use diagnostic pragmas?

The intermediate cast to (__typeof__ ((X) - (X))) is not suffice for x32
(the resulting argumetn it will passed as function argument instead of
asm input).  I have replaced with:

  #define __SSC(__x)                                              \
  ({                                                            \
    __syscall_arg_t __arg = sizeof (1 ? (__x) : 0ULL) < 8       \
      ? (unsigned long int) (uintptr_t)(__x)                    \
      : (__syscall_arg_t) (__typeof__ ((__x) - (__x))) (__x);   \
    __arg;                                                      \
  })