EH in C (was: Re: (lack of) Thread-safe exceptions on AIX (gcc-2.95.1)

[Zack Weinberg]

On Tue, Feb 01, 2000 at 03:37:02PM -0800, Geoff Keating wrote:
> Zack Weinberg <zack@wolery.cumb.org> writes:
> 
> > The usual reason people want exceptions in C is to make pthread
> > cancellation play nice with C++.  The pthread library has 'cleanups'
> > that happen when a thread is cancelled, that are basically
> > try/finally, but they don't interoperate with the C++ exception
> > mechanism.  What you'd like is for pthread_cleanup_push/pop to be
> > implemented in terms of try/catch, and pthread_cancel to throw an
> > exception in the cancelled thread.
> > 
> > That requires only try { } catch (...) { }, plus some way to throw
> > an object (not just rethrow), in C.
> 
> Is there some reason why pthread_cleanup_push/pop can't be implemented
> in C++ (with 'extern "C"', of course)?

I don't think that would help any.  The effect of pthread_cleanup_push
is that if your thread is cancelled between it and the matching
pthread_cleanup_pop, the handler you specified gets called.  To make
that work with the exceptions mechanism, the code in between has to be
exception aware too.

zw