Re: __attribute__((cleanup(function)) versus try/finally

[Fergus Henderson <fjh@cs.mu.OZ.AU>]

On 09-May-2003, Andrew Haley <aph@redhat.com> wrote:
> Actually, the C standard is quite explicit about this: signal handlers
> may return either by a return statement of calling longjmp().

[I think you meant to say "or" instead of "of".]

What you say is true to some extent, but it only applies to signal
handlers for synchronous signals, i.e. those caused by an explicit
call to abort() or raise().  For asynchronous signals, the behaviour
is undefined if the signal handler calls longjmp(), due to 
C99 7.14.1.1 paragraph 5, which prohibits such signal handlers
from calling *any* standard library function other than abort(),
_Exit(), or signal():

 |        If the signal  occurs  other  than  as  the  result  of
 |        calling  the  abort  or  raise  function,  the  behavior  is
 |        undefined if the signal handler refers to  any  object  with
 |        static  storage  duration other than by assigning a value to
 |        an object declared as volatile sig_atomic_t, or  the  signal
 |        handler  calls  any  function  in the standard library other
 |        than the abort function, the _Exit function, or  the  signal
 |        function  with the first argument equal to the signal number
 |        corresponding to the signal that caused  the  invocation  of
 |        the  handler.

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.