Re: [Qemu-devel] [PATCH 4/5] Avoid unportable %m format

[Anthony Liguori]

On 07/10/2012 04:12 PM, Stefan Weil wrote:
> Am 10.07.2012 22:53, schrieb Anthony Liguori:
> > On 07/08/2012 06:51 AM, address@hidden wrote:
> > > From: Blue Swirl<address@hidden>
> > >
> > > Replace %m format with explicit call to standard strerror().
> > >
> > > Signed-off-by: Blue Swirl<address@hidden>
> >
> > I would expect '%m' to be thread safe whereas strerror() isn't. I don't think
> > this change is actually good.
> >
> > You'd need to do something more clever with strerror_r() to be equivalent.
> >
> > Regards,
> >
> > Anthony Liguori
>
> Extract from the Linux manpage PRINTF(3):
>
> m (Glibc extension.) Print output of strerror(errno). No argument is required.

You're reading the docs too literally:

http://sourceware.org/git/?p=glibc.git;a=blob;f=stdio-common/vfprintf.c;h=d5690342536bc8cf948c786f663bb63f73f91f3a;hb=HEAD#l966

It uses strerror_r() and is thread-safe.  Converting to strerror() removes that 
safety.

Regards,

Anthony Liguori