Re: Unix.localtime not threadsafe?

[Bardur Arantsson <spam@scientician.net>]

Yaron Minsky wrote:
> I was looking at the Unix.localtime implementation, and it appears to
> me that it's not threadsafe.  I'm wondering if anyone can confirm.
> 
> First off, the underlying localtime call is definitely not re-entrant.
>  The tm data structure is shared among all calls, leading to the
> possibility of races.  What I'm not sure of is whether there can be a
> race given the locking of the OCaml runtime.  Here's the code from
> gmtime.c in the ocaml distribution:

I don't think the glibc/Linux localtime() man page explicitly states 
this, but I expect that it returns a pointer to a *thread-local* 
statically allocated struct tm... in which case there's no problem.

Most other system functions whose API looks non-threadsafe do the same. 
('errno' would be the standard example).

[--snip--]

-- 
Bardur Arantsson
<bardur@imada.sdu.dk>
<bardur@scientician.net>

- But don't be reading my mind between 4 and 5. That's Willie's
time!
                              Groundskeeper Willie, 'The Simpsons'