Re: [PATCH] tile: use better variable naming in INLINE_SYSCALL

[Chris Metcalf <cmetcalf@ezchip.com>]

On 5/26/2015 4:44 PM, Carlos O'Donell wrote:
> On 05/26/2015 02:19 PM, Chris Metcalf wrote:
>> At issue for INLINE_SYSCALL was that it used "err" and "val"
>> as variable names in a #define, so that if it was used in a context
>> where the "caller" was also using "err" or "val", and those
>> variables were passed in to INLINE_SYSCALL, we would end up
>> referencing the internal shadowed variables instead.
>>
>> For example, "char val" in check_may_shrink_heap() in
>> sysdeps/unix/sysv/linux/malloc-sysdep.h was being shadowed by
>> the syscall return "val" in INLINE_SYSCALL, causing the "char val"
>> not to get updated at all, and may_shrink_heap ended up always false.
>>
>> A similar fix was made to INTERNAL_VSYSCALL_CALL.
> Established practice appears to be to use `sc_err`.
>
> A quick look shows that other sysdep.h also suffer this problem,
> but have been lucky that nobody uses `sc_ret` or similarly named
> variables in the outer scope.
>
> Doesn't this also impact MIPS, Microblaze, SPARC and NIOS2?
>
> sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h:  ({ INTERNAL_SYSCALL_DECL(err);					\
> sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h:#undef INTERNAL_SYSCALL_DECL
> sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h:  ({ INTERNAL_SYSCALL_DECL(err);					\
> sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h:#undef INTERNAL_SYSCALL_DECL
> sysdeps/unix/sysv/linux/mips/mips32/sysdep.h:  ({ INTERNAL_SYSCALL_DECL(err);					\
> sysdeps/unix/sysv/linux/mips/mips32/sysdep.h:#undef INTERNAL_SYSCALL_DECL
> sysdeps/unix/sysv/linux/microblaze/sysdep.h:({  INTERNAL_SYSCALL_DECL(err);                                      \
> sysdeps/unix/sysv/linux/microblaze/sysdep.h:# undef INTERNAL_SYSCALL_DECL
> sysdeps/unix/sysv/linux/sparc/sysdep.h:({	INTERNAL_SYSCALL_DECL(err);  					\
> sysdeps/unix/sysv/linux/sparc/sysdep.h:#undef INTERNAL_SYSCALL_DECL
> sysdeps/unix/sysv/linux/nios2/sysdep.h:  ({ INTERNAL_SYSCALL_DECL(err);					\
> sysdeps/unix/sysv/linux/nios2/sysdep.h:#undef INTERNAL_SYSCALL_DECL
>
> I dislike the use of `sc_err`, and I'd rather blanket fix
> *every* port to use `_sc_err` instead, but that's just me.
>
> Fixing tile is more than good enough.

Thanks for looking at this, and you're right that probably fixing everything is
a better approach, but one that I was too lazy to undertake this minute.  :-)
I updated my change to use _sc_err instead of _sys_err (likewise for _sc_val) and
committed.

This is the convention already used in sysdeps/unix/alpha/sysdep.h, by the way.

-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com