On 22/01/2019 19.10, Eric Blake wrote: > On 1/22/19 11:23 AM, Daniel P. Berrangé wrote: > >> >>>> On this point though, does anyone know of any platforms we support[1], >>>> or are likely to support in future, where 'strerror' is *not* thread >>>> safe ? >>> >>> I'm not coming up with one, and I think the problem is independent of >>> this series (if we DO have a problem, it's a series all its own to >>> eradicate the use of strerror() in favor of something safer, either >>> picking strerror_l() or dealing with the glibc vs. BSD differences in >>> strerror_r()). >> >> Agree that its not really something for this series - this just >> made me think of it again. > > Shoot - FreeBSD strerror() is not threadsafe: > https://github.com/freebsd/freebsd/blob/master/lib/libc/string/strerror.c#L119 > > char * > strerror(int num) > { > static char ebuf[NL_TEXTMAX]; > > if (strerror_r(num, ebuf, sizeof(ebuf)) != 0) > errno = EINVAL; > return (ebuf); > } > >> >> We went through the scrubbing in libvirt to use the sane, but still >> tedious to call, variant of strerror_r() many years ago. With luck >> though it is a worry that can be confined the dustbin of ancient >> UNIX history....unless someone can point to evidence to the contrary ? > > libvirt has it easy - they let gnulib do all the work of futzing around > with getting a working strerror() despite platform bugs and despite > glibc's insistence on a non-POSIX signature if _GNU_SOURCE is defined. > We'll have to do a bit more legwork. > > That said, I've added it to: > https://wiki.qemu.org/Contribute/BiteSizedTasks#Error_checking > > if someone wants to do the grunt work.
I think we should change that task to switch to g_strerror() from glib instead ... as far as I can see, this is a proper wrapper around strerror_r(), so we don't have to deal with the implementation oddities of strerror_r() in QEMU. Thomas
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