Re: [Qemu-trivial] [Qemu-devel] [PATCH] util/qemu-thread-posix.c: Replace OS ifdefs with CONFIG_HAVE_SEM_TIMEDWAIT

[Eric Blake]

On 09/05/2017 07:19 AM, Peter Maydell wrote:
> In qemu-thread-posix.c we have two implementations of the
> various qemu_sem_* functions, one of which uses native POSIX
> sem_* and the other of which emulates them with pthread conditions.
> This is necessary because not all our host OSes support
> sem_timedwait().
> 
> Instead of a hard-coded list of OSes which don't implement
> sem_timedwait(), which gets out of date, make configure
> test for the presence of the function and set a new
> CONFIG_HAVE_SEM_TIMEDWAIT appropriately.
> 
> In particular, newer NetBSDs have sem_timedwait(), so this
> commit will switch them over to using it. OSX still does
> not have an implementation.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> It would be nice to gradually reduce the number of places
> we do per-OS ifdeffery in favour of checking for the specific
> feature we care about in each case...

Yes, that's always been autoconf's philosophy: feature tests trump
platform tests every time, because platforms can add features over time,
and because an ifdef on a single feature test is easier to read than a
list of platform names.

> Tested on Linux, NetBSD, OSX.
> 

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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