This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: Calling other functions while concurrently calling exit?
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Rich Felker <dalias at aerifal dot cx>
- Cc: Andreas Schwab <schwab at linux-m68k dot org>, Carlos O'Donell <carlos at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>, Torvald Riegel <triegel at redhat dot com>
- Date: Tue, 22 Sep 2015 21:42:08 +0200
- Subject: Re: Calling other functions while concurrently calling exit?
- Authentication-results: sourceware.org; auth=none
- References: <55FCD13B dot 8030000 at redhat dot com> <87fv2aoqfe dot fsf at igel dot home> <20150919101041 dot GA15324 at domone> <20150919142637 dot GH17773 at brightrain dot aerifal dot cx>
On Sat, Sep 19, 2015 at 10:26:37AM -0400, Rich Felker wrote:
> On Sat, Sep 19, 2015 at 12:10:41PM +0200, OndÅej BÃlka 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.