Bug 650161 - Add API to disable compacting GC r=terrence

js/public/GCAPI.h

@@ -285,6 +285,21 @@ DisableIncrementalGC(JSRuntime *rt);
 extern JS_FRIEND_API(bool)
 IsIncrementalGCEnabled(JSRuntime *rt);
 
+/*
+ * Compacting GC defaults to enabled, but may be disabled for testing or in
+ * embeddings that have not implemented the necessary object moved hooks or weak
+ * pointer callbacks.  There is not currently a way to re-enable compacting GC
+ * once it has been disabled on the runtime.
+ */
+extern JS_FRIEND_API(void)
+DisableCompactingGC(JSRuntime *rt);
+
+/*
+ * Returns true if compacting GC is enabled.
+ */
+extern JS_FRIEND_API(bool)
+IsCompactingGCEnabled(JSRuntime *rt);
+
 /*
  * Returns true while an incremental GC is ongoing, both when actively
  * collecting and between slices.

js/src/gc/GCRuntime.h

@@ -444,6 +444,7 @@ class GCRuntime
 #ifdef JSGC_COMPACTING
     void disableCompactingGC();
     void enableCompactingGC();
+    bool isCompactingGCEnabled();
 #endif
 
     void setGrayRootsTracer(JSTraceDataOp traceOp, void *data);

js/src/jsfriendapi.cpp

@@ -1125,6 +1125,24 @@ JS::DisableIncrementalGC(JSRuntime *rt)
     rt->gc.disallowIncrementalGC();
 }
 
+JS_FRIEND_API(void)
+JS::DisableCompactingGC(JSRuntime *rt)
+{
+#ifdef JSGC_COMPACTING
+    rt->gc.disableCompactingGC();
+#endif
+}
+
+JS_FRIEND_API(bool)
+JS::IsCompactingGCEnabled(JSRuntime *rt)
+{
+#ifdef JSGC_COMPACTING
+    return rt->gc.isCompactingGCEnabled();
+#else
+    return false;
+#endif
+}
+
 JS::AutoDisableGenerationalGC::AutoDisableGenerationalGC(JSRuntime *rt)
   : gc(&rt->gc)
 #if defined(JSGC_GENERATIONAL) && defined(JS_GC_ZEAL)

js/src/jsgc.cpp

@@ -2005,7 +2005,7 @@ bool
 GCRuntime::shouldCompact()
 {
 #ifdef JSGC_COMPACTING
-    return invocationKind == GC_SHRINK && !compactingDisabled;
+    return invocationKind == GC_SHRINK && isCompactingGCEnabled();
 #else
     return false;
 #endif
@@ -2026,6 +2026,12 @@ GCRuntime::enableCompactingGC()
     --compactingDisabled;
 }
 
+bool
+GCRuntime::isCompactingGCEnabled()
+{
+    return rt->gc.compactingDisabled == 0;
+}
+
 AutoDisableCompactingGC::AutoDisableCompactingGC(JSRuntime *rt)
   : gc(rt->gc)
 {