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Re: [PATCH][AArch64] change greg_t definition in ucontext.h
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Cc: Marcus Shawcroft <marcus dot shawcroft at arm dot com>, Ramana Radhakrishnan <Ramana dot Radhakrishnan at arm dot com>
- Date: Thu, 21 May 2015 14:21:45 -0400
- Subject: Re: [PATCH][AArch64] change greg_t definition in ucontext.h
- Authentication-results: sourceware.org; auth=none
- References: <555E0986 dot 3010608 at arm dot com>
On 05/21/2015 12:36 PM, Szabolcs Nagy wrote:
> This change assumes greg_t is not used outside of libc.
> In glibc it is usually used for defining gregset_t, but
> on aarch64 elf_greg_t is used for that, greg_t is not
> used anywhere (so it is meant to be a cosmetic fix).
>
> If greg_t is used outside of libc, then this is an ABI
> change, but
>
> typedef int greg_t;
>
> is not a useful definition on aarch64.
>
> Some targets (powerpc) don't define greg_t at all so
> removing it should be a valid fix too. It seems the
> signedness of greg_t varies between targets so i settled
> for using elf_greg_t (unsigned long) for the typedef to
> be consistent with the members of gregset_t.
>
>
> Changelog:
>
> 2015-05-07 Szabolcs Nagy <szabolcs.nagy@arm.com>
>
> * sysdeps/unix/sysv/linux/aarch64/sys/ucontext.h (greg_t): Change the
> definition to elf_greg_t.
>
OK for me.
I agree it is not a useful definition for aarch64,
however, it is technically an ABI break.
As long as you acknowledge that you are breaking
the ABI for this type, then you can go ahead, but
something in userspace *might* break.
The only other component I've seen use greg_t is
gdb, but on aarch64 you don't use greg_t, and if
you did you would have discovered this was broken
earlier.
Cheers,
Carlos.