[PATCH] Ensure the default purgeable zone is after the default zone on OS X

[Mike Hommey]

From: Mike Hommey <mh at glandium.org>

---
 src/zone.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/src/zone.c b/src/zone.c
index e0302ef..a722287 100644
--- a/src/zone.c
+++ b/src/zone.c
@@ -176,6 +176,7 @@ register_zone(void)
 	 * register jemalloc's.
 	 */
 	malloc_zone_t *default_zone = malloc_default_zone();
+	malloc_zone_t *purgeable_zone = NULL;
 	if (!default_zone->zone_name ||
 	    strcmp(default_zone->zone_name, "DefaultMallocZone") != 0) {
 		return;
@@ -237,22 +238,37 @@ register_zone(void)
 	 * run time.
 	 */
 	if (malloc_default_purgeable_zone != NULL)
-		malloc_default_purgeable_zone();
+		purgeable_zone = malloc_default_purgeable_zone();
 
 	/* Register the custom zone.  At this point it won't be the default. */
 	malloc_zone_register(&zone);
 
-	/*
-	 * Unregister and reregister the default zone.  On OSX >= 10.6,
-	 * unregistering takes the last registered zone and places it at the
-	 * location of the specified zone.  Unregistering the default zone thus
-	 * makes the last registered one the default.  On OSX < 10.6,
-	 * unregistering shifts all registered zones.  The first registered zone
-	 * then becomes the default.
-	 */
 	do {
 		default_zone = malloc_default_zone();
+		/*
+		 * Unregister and reregister the default zone.  On OSX >= 10.6,
+		 * unregistering takes the last registered zone and places it
+		 * at the location of the specified zone.  Unregistering the
+		 * default zone thus makes the last registered one the default.
+		 * On OSX < 10.6, unregistering shifts all registered zones.
+		 * The first registered zone then becomes the default.
+		 */
 		malloc_zone_unregister(default_zone);
 		malloc_zone_register(default_zone);
+		/*
+		 * On OSX 10.6, having the default purgeable zone appear before
+		 * the default zone makes some things crash because it thinks it
+		 * owns the default zone allocated pointers. We thus unregister/
+		 * re-register it in order to ensure it's always after the
+		 * default zone. On OSX < 10.6, there is no purgeable zone, so
+		 * this does nothing. On OSX >= 10.6, unregistering replaces the
+		 * purgeable zone with the last registered zone above, i.e the
+		 * default zone. Registering it again then puts it at the end,
+		 * obviously after the default zone.
+		 */
+		if (purgeable_zone) {
+			malloc_zone_unregister(purgeable_zone);
+			malloc_zone_register(purgeable_zone);
+		}
 	} while (malloc_default_zone() != &zone);
 }
-- 
2.0.0.rc2