[svn-r12019] Purpose:

Bug fix/Feature

Description:
Modify the library to use rand_r, when available, instead of srand.  If
rand_r is not available, it will try to use srandom/random, and then finally
fall back to srand/rand.

Solution:
A couple places in the library use the srand() function to seed the random
number generator.  This can cause problems on certain platforms and could theoretically
cause problems for users who expect a certain sequence of random numbers following their
own call to srand().

Most platforms have an implementation of rand_r, which is identical to rand, except that
it allows for explicit storage of the seed value.  The configure script will now check
for the existence of rand_r to facilitate its use in the library.

Two new functions are added, to replace the macros HDsrand/HDrand.  These functions are HDrand and
HDsrand.  HDrand will call rand_r, if available, or random(), if available, and fall back to rand() if neither
of those is available.  HDsrand will store the seed value locally, if rand_r is available.  Otherwise, it will call
srandom if available, and fall back to srand otherwise.


Platforms tested:
heping, mir.  Really need to test on Red Storm, since that platform motivated this fix, but the machine
is currently not available.

Misc. update:

1 files changed, 45 insertions, 0 deletions

diff --git a/src/H5.c b/src/H5.c
index 0476dbb..6f13e9c 100644
--- a/src/H5.c
+++ b/src/H5.c
@@ -3114,3 +3114,48 @@ H5_trace (const double *returning, const char *func, const char *type, ...)
     HDfflush (out);
     return event_time.etime;
 }
+
+/*-------------------------------------------------------------------------
+ * Function:	HDrand/HDsrand
+ *
+ * Purpose:	Wrapper function for rand.  If rand_r exists on this system,
+ * 		use it.  Otherwise, just call random() or rand().
+ *
+ * 		Wrapper function for srand.  If rand_r is available, it will keep
+ * 		track of the seed locally instead of using srand() which modifies
+ * 		global state and can break other programs.  Otherwise, just call
+ * 		srandom() or srand().
+ *
+ * Return:	Success:	Random number from 0 to RAND_MAX
+ *
+ *		Failure:	Cannot fail.
+ *
+ * Programmer:	Leon Arber
+ *              March 6, 2006.
+ *
+ * Modifications:
+ *-------------------------------------------------------------------------
+ */
+static unsigned int g_seed = 42;
+
+int HDrand(void)
+{
+#ifdef H5_HAVE_RAND_R
+    return rand_r(&g_seed);
+#elif H5_HAVE_RANDOM
+    return random();
+#else
+    return rand();
+#endif
+}
+
+void HDsrand(unsigned int seed)
+{
+#ifdef H5_HAVE_RAND_R
+    g_seed = seed; 
+#elif H5_HAVE_RANDOM
+    return srandom(seed);
+#else
+    return srand(seed);
+#endif
+}