| Message ID | mvmr3q2l1yr.fsf@hawking.suse.de |
|---|---|
| State | New |
| Headers | show |
On Fri, May 29, 2015 at 3:32 AM, Chris Metcalf <cmetcalf@ezchip.com> wrote: > On 05/27/2015 07:00 AM, Andreas Schwab wrote: >> >> sem_t must have the same alignment as struct new_sem. >> >> Andreas. >> >> * sysdeps/aarch64/nptl/bits/semaphore.h (sem_t) [!__LP64__]: Use >> long long for __align. >> --- >> sysdeps/aarch64/nptl/bits/semaphore.h | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/sysdeps/aarch64/nptl/bits/semaphore.h >> b/sysdeps/aarch64/nptl/bits/semaphore.h >> index 047dd4e..d9f4ab6 100644 >> --- a/sysdeps/aarch64/nptl/bits/semaphore.h >> +++ b/sysdeps/aarch64/nptl/bits/semaphore.h >> @@ -31,5 +31,9 @@ >> typedef union >> { >> char __size[__SIZEOF_SEM_T]; >> +#ifdef __LP64__ >> long int __align; >> +#else >> + long long int __align; >> +#endif >> } sem_t; > > > Why not unconditionally use "long long" as the type? Or if you really > prefer > the different types, just use "__INT64_TYPE__ __align" instead? Either way > seems like it makes the code a little more readable, though I'd prefer > the former (and it is more friendly to non-gcc compilers). > > More generally, I'm not sure why we don't just use > __attribute__((aligned(8))) > on a simple struct holding the __size[] array, rather than playing union > games. > Obviously this still would have to be per-platform due to > __HAVE_64B_ATOMICS, > but just explicitly specifying the alignment does seem cleaner. I guess it > is > arguably more friendly to non-gcc compilers using the public headers to > do it the way it has been done traditionally. > > None of these suggestions change C++ type mangling as far as I can see, > so are presumably all safe from an ABI perspective. Or better yet use __kernel_signed_long type. Thanks, Andrew > > -- > Chris Metcalf, EZChip Semiconductor > http://www.ezchip.com >
Andrew Pinski <pinskia@gmail.com> writes:
> Or better yet use __kernel_signed_long type.
This has nothing to do with the kernel. It's a pure user-space
requirement that sem_t must be 64-bit aligned.
Andreas.
diff --git a/sysdeps/aarch64/nptl/bits/semaphore.h b/sysdeps/aarch64/nptl/bits/semaphore.h index 047dd4e..d9f4ab6 100644 --- a/sysdeps/aarch64/nptl/bits/semaphore.h +++ b/sysdeps/aarch64/nptl/bits/semaphore.h @@ -31,5 +31,9 @@ typedef union { char __size[__SIZEOF_SEM_T]; +#ifdef __LP64__ long int __align; +#else + long long int __align; +#endif } sem_t;