Re: [PATCH] cdefs: Limit definition of fortification macros

[Florian Weimer <fweimer@redhat.com>]

* Siddhesh Poyarekar:

> Define the __glibc_fortify and other macros only when __FORTIFY_LEVEL >
> 0.  This has the effect of not defining these macros on older C90
> compilers that do not have support for variable length argument lists.
>
> Also trim off the trailing backslashes from the definition of
> __glibc_fortify and __glibc_fortify_n macros.
>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
>
> Only tested for sanity.  Florian, can you please verify that this
> resolves the original problem?
>
>  misc/sys/cdefs.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
> index 66d6702123..c37a3ff637 100644
> --- a/misc/sys/cdefs.h
> +++ b/misc/sys/cdefs.h
> @@ -152,6 +152,7 @@
>  # define __glibc_objsize(__o) __bos (__o)
>  #endif
>  
> +#if __USE_FORTIFY_LEVEL > 0
>  /* Compile time conditions to choose between the regular, _chk and _chk_warn
>     variants.  These conditions should get evaluated to constant and optimized
>     away.  */
> @@ -187,7 +188,7 @@
>     ? __ ## f ## _alias (__VA_ARGS__)					      \
>     : (__glibc_unsafe_len (__l, __s, __osz)				      \
>        ? __ ## f ## _chk_warn (__VA_ARGS__, __osz)			      \
> -      : __ ## f ## _chk (__VA_ARGS__, __osz)))			      \
> +      : __ ## f ## _chk (__VA_ARGS__, __osz)))
>  
>  /* Fortify function f, where object size argument passed to f is the number of
>     elements and not total size.  */
> @@ -197,7 +198,8 @@
>     ? __ ## f ## _alias (__VA_ARGS__)					      \
>     : (__glibc_unsafe_len (__l, __s, __osz)				      \
>        ? __ ## f ## _chk_warn (__VA_ARGS__, (__osz) / (__s))		      \
> -      : __ ## f ## _chk (__VA_ARGS__, (__osz) / (__s))))		      \
> +      : __ ## f ## _chk (__VA_ARGS__, (__osz) / (__s))))
> +#endif
>  
>  #if __GNUC_PREREQ (4,3)
>  # define __warnattr(msg) __attribute__((__warning__ (msg)))

Seems reasonable, thanks.  I believe it works with those old compilers.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

Florian