Re: Thread-, Signal- and Cancellation-safety documentation

[Florian Weimer <fweimer at redhat dot com>]

On 05/19/2013 09:31 AM, Alexandre Oliva wrote:
> On May 17, 2013, Torvald Riegel <triegel@redhat.com> wrote:
>
> > * There's no clear definition of whether "thread-safe" is about...
>
> There's a clear definition of the specified behavior for each function,
> so âfunction F is safe to callâ ought to mean âF behaves as specifiedâ.

But this is clearly wrong for functions such as chdir().  You really 
shouldn't call them in multi-threaded programs, but they still work 
exactly as specified.

For the standard, a very narrow (or broad, depending on your 
perspective) view of what constitutes "thread-safe" makes sense, but for 
the glibc documentation, we should aim to provide useful guidance for 
developers and focus on the question if the function is actually usable 
in a multi-threaded context.  Sometimes, there will be an overlap (say, 
strtok), sometimes, glibc will consider functions thread-safe which 
aren't in the standard (readdir), sometimes, the standard will label 
things thread-safe which aren't from our perspective (chdir).

--
Florian Weimer / Red Hat Product Security Team