Calling other functions while concurrently calling exit?

[Ondřej Bílka]

On Sat, Sep 19, 2015 at 10:26:37AM -0400, Rich Felker wrote:
> On Sat, Sep 19, 2015 at 12:10:41PM +0200, Ondřej Bílka wrote:
> > On Sat, Sep 19, 2015 at 08:48:21AM +0200, Andreas Schwab wrote:
> > > "Carlos O'Donell" <carlos@redhat.com> writes:
> > > 
> > > > Is it spelled out anywhere in POSIX or ISO C that calling
> > > > other functions concurrently with exit is going to result
> > > > in undefined behaviour?
> > > 
> > > exit must be thread-safe, except that calling it more than once is
> > > undefined.
> > > 
> > Wait, we don't do sane thing and first cancel all other threads before doing anything?
> 
> You cannot cancel threads that are currently running code that was not
> designed to be cancellable. Doing so is extremely dangerous.
> 
And could you explain how that is different from situation now where
exit will terminate all threads so you will get inconsistent state
anyway?

> > How otherwise we would run tls destructors in context of correct thread?
> 
> TLS destructors only run when the thread exit, either by being the one
> to call exit or by exiting as a thread (e.g. pthread_exit). This is
> all specified.
> 
While true its bad design, C++ programmers would be often surprised that destructors that close files, unlock process shared locks or so don't run.