[vlc-commits] commit: Work-around non-thread-safe use of the C random number generator ( Rémi Denis-Courmont )

[git at videolan.org]

vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Sun Apr 11 18:37:49 2010 +0300| [4213a133fd1ef14fd9b62620412a45af091d73ae] | committer: Rémi Denis-Courmont 

Work-around non-thread-safe use of the C random number generator

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=4213a133fd1ef14fd9b62620412a45af091d73ae
---

 bin/override.c |   31 +++++++++++++++++++++++++++++++
 1 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/bin/override.c b/bin/override.c
index 5098a7d..2f7606b 100644
--- a/bin/override.c
+++ b/bin/override.c
@@ -41,6 +41,7 @@ void vlc_enable_override (void)
 #include <stdio.h>
 #include <stdlib.h>
 #include <dlfcn.h>
+#include <pthread.h>
 
 static void vlogbug (const char *level, const char *func, const char *fmt,
                      va_list ap)
@@ -116,4 +117,34 @@ int unsetenv (const char *name)
 }
 
 
+/*** Pseudo random numbers ***
+ *
+ * The C PRNG is not thread-safe (and generally sucks, the POSIX 48-bits PRNG
+ * is much better as a reproducible non-secure PRNG). To work around this, we
+ * force evil callers to serialize. This makes the call safe, but fails to
+ * preserve reproducibility of the number sequence (which usually does not
+ * matter).
+ **/
+static pthread_mutex_t prng_lock = PTHREAD_MUTEX_INITIALIZER;
+
+void srand (unsigned int seed)
+{
+    pthread_mutex_lock (&prng_lock);
+    LOG("Warning", "%d", seed);
+    CALL(srand, seed);
+    pthread_mutex_unlock (&prng_lock);
+}
+
+int rand (void)
+{
+    int ret;
+
+    pthread_mutex_lock (&prng_lock);
+    LOG("Warning", "");
+    ret = CALL(rand);
+    pthread_mutex_unlock (&prng_lock);
+    return ret;
+}
+
+
 #endif /* __ELF__ */