teedee wrote on 2006-03-27:
> Is localtime_r thread-safe? If it's not, what's the alternative for this
> function call?
localtime_r is thread-safe if the system provides it and it has the POSIX
prototype: struct tm * localtime_r (const time_t *, struct tm *);
In the other cases, gnulib provides a replacement that has the right prototype
but is not thread-safe.
The alternative is to use the time() function and convert to local time
yourself.
Paul, what about the following patch to make our replacement functions MT-safe?
2006-04-27 Bruno Haible <[EMAIL PROTECTED]>
Make gmtime_r and localtime_r replacements multithread-safe.
* time_r.c: Include lock.h.
(bufferlock): New variable.
(gmtime_r, localtime_r): Protect against concurrent use.
* modules/time_r: Depend on module lock.
diff -c -3 -r1.6 time_r.c
*** lib/time_r.c 25 Mar 2006 04:36:14 -0000 1.6
--- lib/time_r.c 27 Apr 2006 13:42:37 -0000
***************
*** 25,30 ****
--- 25,31 ----
#include "time_r.h"
#include <string.h>
+ #include "lock.h"
static struct tm *
copy_tm_result (struct tm *dest, struct tm const *src)
***************
*** 35,49 ****
return dest;
}
struct tm *
gmtime_r (time_t const * restrict t, struct tm * restrict tp)
{
! return copy_tm_result (tp, gmtime (t));
}
struct tm *
localtime_r (time_t const * restrict t, struct tm * restrict tp)
{
! return copy_tm_result (tp, localtime (t));
}
--- 36,64 ----
return dest;
}
+ /* A lock protecting the static buffers holding the return values of
+ gmtime() and localtime(). We use a single lock, not two locks, because
+ it might be a single buffer for both functions. */
+ gl_lock_define_initialized(static, bufferlock)
struct tm *
gmtime_r (time_t const * restrict t, struct tm * restrict tp)
{
! struct tm *result;
!
! gl_lock_lock (bufferlock);
! result = copy_tm_result (tp, gmtime (t));
! gl_lock_unlock (bufferlock);
! return result;
}
struct tm *
localtime_r (time_t const * restrict t, struct tm * restrict tp)
{
! struct tm *result;
!
! gl_lock_lock (bufferlock);
! result = copy_tm_result (tp, localtime (t));
! gl_lock_unlock (bufferlock);
! return result;
}
diff -c -3 -r1.6 time_r
*** modules/time_r 12 Apr 2006 16:50:51 -0000 1.6
--- modules/time_r 27 Apr 2006 13:42:37 -0000
***************
*** 7,12 ****
--- 7,13 ----
m4/time_r.m4
Depends-on:
+ lock
extensions
restrict
