Re: [Qemu-devel] [PATCH V2 1/3] Darwin: Fix incorrect check for fdatasync() in configure

["Andreas Färber" <andreas.faerber@web.de>]

Am 30.05.2011 um 00:22 schrieb Alexandre Raymond:

> Under darwin (OS X 10.6.7), a symbol exists for the fdatasync() method
> but it is not supported because _POSIX_SYNCHRONIZED_IO is set to '-1'.

Question: How did you notice? Did anything break that we could  
mention, or did you just review the code?

> Enable fdatasync() only if _POSIX_SYNCHRONIZED_IO is '>0', as per
> The Open Group Base Specifications Issue 7.

Not quite what I meant. ;) Would you be okay with the following:

configure: Fix check for fdatasync()

Under Darwin, a symbol exists for the fdatasync() function, but it is
not supported. Yada yada. _POSIX_SYNCHRONIZED_IO is set to '-1'.

According to POSIX:2008, a value of -1 means the feature is not  
supported.
A value of 0 means supported at compilation time, and a value greater 0
means supported at both compilation and run time.

Enable fdatasync() only if _POSIX_SYNCHRONIZED_IO is '>0'.

Andreas

> Signed-off-by: Alexandre Raymond <cerbere@gmail.com>
> ---
> configure |    8 +++++++-
> 1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/configure b/configure
> index a318d37..b21ef75 100755
> --- a/configure
> +++ b/configure
> @@ -2477,7 +2477,13 @@ fi
> fdatasync=no
> cat > $TMPC << EOF
> #include <unistd.h>
> -int main(void) { return fdatasync(0); }
> +int main(void) {
> +#if defined(_POSIX_SYNCHRONIZED_IO) && _POSIX_SYNCHRONIZED_IO > 0
> +return fdatasync(0);
> +#else
> +#abort Not supported
> +#endif
> +}
> EOF
> if compile_prog "" "" ; then
>     fdatasync=yes
> -- 
> 1.7.5
>