Re: Fix signal handler

[Jeff King <peff@peff.net>]

On Tue, Feb 02, 2010 at 10:44:37PM +0100, Markus Elfring wrote:

> > No, it's not a sig_atomic_t, but it is assignment of a single function
> > pointer that is properly declared as volatile. Is this actually a
> > problem on any known system?
> 
> Is it guaranteed to work on all supported software environments that an
> address can be atomically set?

I think you are missing my point. We are not coding to a set of
standards that provide guarantees. We are coding to a practical set of
real-world implementations that people try to run git on and produce bug
reports for. I do not think anyone on this list could even enumerate a
complete a list of the "supported software environments" of git.

We try to be conservative about portability issues. Some things are
obviously wrong. But other things may violate the letter of some
standards, and yet work in practice on all of the platforms people are
interested in running git on.

I don't think anyone here is much interested in whether there is any
sort of guarantee on a particular construct working. What we do care
about is whether there is an actual problem on some platform that enough
people care about to justify rewriting the code to handle it.

So to answer your question, I honestly don't know. The code may well be
broken on common platforms and it is simply a race condition that has
never come up. But I do know that it has not been a common source of bug
reports, which makes me not want to spend time investigating it when
nobody has demonstrated its incorrectness beyond mentioning a standards
document.  Especially when that time could be better spent fixing other
bugs.

-Peff