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Re: [PATCH] Fix sh4 build with __ASSUME_ST_INO_64_BIT redefinition
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: <libc-alpha at sourceware dot org>
- Date: Thu, 10 Nov 2016 18:07:02 +0000
- Subject: Re: [PATCH] Fix sh4 build with __ASSUME_ST_INO_64_BIT redefinition
- Authentication-results: sourceware.org; auth=none
- References: <1478695312-5009-1-git-send-email-adhemerval.zanella@linaro.org>
On Wed, 9 Nov 2016, Adhemerval Zanella wrote:
> It is because sh4 kernel-features.sh is included multiple times
> without guards and this patch fixes by adding them. Tested on a
> sh4-linux-gnu build.
>
> Also with this issues, is there are strong reason to *not* have include guards
> on kernel-features.h? With current approach, a architecture can't include
> Linux default kernel-features.h and redefine it to a different value, only
> undefine it (unless it explicit do not include default kernel-features.h,
> and I think that's is not the idea).
>
> * sysdeps/unix/sysv/linux/sh/kernel-features.h: Add include
> guards.
OK. I think it's appropriate for all these headers to have include
guards.
The #ifndef, #undef etc. could be avoided (moving this header closer to
glibc's macro-name-typo-proof norms in this regard) if the header were
split up into smaller pieces for individual macros or groups of related
macros whenever a macro's definition needs to vary between architectures.
Thus, you'd have e.g. kernel-features-st-ino.h defining
__ASSUME_ST_INO_64_BIT to either 0 or 1, the default version of that
header would define to 0 and the architectures overriding it would define
to 1 (and wouldn't need #include_next). kernel-features.h could end up as
an architecture-independent header that just #includes the smaller
architecture-specific headers. (This is not a full design, especially for
the more complicated cases such as socket syscalls.)
--
Joseph S. Myers
joseph@codesourcery.com