From: Greg Hazel <ghazel@gmail.com>
Date: Tue, 29 May 2012 19:39:12 +0000 (-0700)
Subject: check for arc4random_buf at runtime, on OS X
X-Git-Tag: release-2.0.20-stable~26
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bff5f9407341030c77a29fc1c398083ccdb4e277;p=libevent

check for arc4random_buf at runtime, on OS X

(Tweaked by nickm: Fix up the arcr4andom_buf OSX hack so that the
fallback case isn't compiled into the code when we have
arc4random_buf() and we are not on OSX.  Also add a comment
explaining what's up.)
---

diff --git a/evutil_rand.c b/evutil_rand.c
index 3cc163d3..e2bf605f 100644
--- a/evutil_rand.c
+++ b/evutil_rand.c
@@ -58,10 +58,22 @@ evutil_secure_rng_global_setup_locks_(const int enable_locks)
 static void
 ev_arc4random_buf(void *buf, size_t n)
 {
-#ifdef _EVENT_HAVE_ARC4RANDOM_BUF
+	unsigned char *b = buf;
+#if defined(_EVENT_HAVE_ARC4RANDOM_BUF) && !defined(__APPLE__)
 	return arc4random_buf(buf, n);
 #else
-	unsigned char *b = buf;
+
+#if defined(_EVENT_HAVE_ARC4RANDOM_BUF)
+	/* OSX 10.7 introducd arc4random_buf, so if you build your program
+	 * there, you'll get surprised when older versions of OSX fail to run.
+	 * To solve this, we can check whether the function pointer is set,
+	 * and fall back otherwise.  (OSX does this using some linker
+	 * trickery.)
+	 */
+	if (arc4random_buf) {
+		return arc4random_buf(buf, n);
+	}
+#endif
 	/* Make sure that we start out with b at a 4-byte alignment; plenty
 	 * of CPUs care about this for 32-bit access. */
 	if (n >= 4 && ((ev_uintptr_t)b) & 3) {