Bug 990787, part 1 - When JSObject::shrinkElements can't reallocate the array to shrink it, clear the OOM exception, as we are not going to propagate the error. r=shu.

--HG--
extra : rebase_source : 42d1d8c25a0b31d20b137ca4f2ff7f592e7fdcd8

js/src/jscntxt.cpp

@@ -1056,7 +1056,7 @@ js::HandleExecutionInterrupt(JSContext *cx)
     return true;
 }
 
-js::ThreadSafeContext::ThreadSafeContext(JSRuntime *rt, PerThreadData *pt, ContextKind kind)
+ThreadSafeContext::ThreadSafeContext(JSRuntime *rt, PerThreadData *pt, ContextKind kind)
   : ContextFriendFields(rt),
     contextKind_(kind),
     perThreadData(pt),
@@ -1077,6 +1077,25 @@ ThreadSafeContext::asForkJoinContext()
     return reinterpret_cast<ForkJoinContext *>(this);
 }
 
+void
+ThreadSafeContext::recoverFromOutOfMemory()
+{
+    // If this is not a JSContext, there's nothing to do.
+    if (JSContext *maybecx = maybeJSContext()) {
+        if (maybecx->isExceptionPending()) {
+#ifdef DEBUG
+            RootedValue v(maybecx);
+            bool ok = maybecx->getPendingException(&v);
+            MOZ_ASSERT(ok);
+            MOZ_ASSERT(v == StringValue(maybecx->names().outOfMemory));
+#endif
+            maybecx->clearPendingException();
+        } else {
+            MOZ_ASSERT(maybecx->runtime()->hadOutOfMemory);
+        }
+    }
+}
+
 JSContext::JSContext(JSRuntime *rt)
   : ExclusiveContext(rt, &rt->mainThread, Context_JS),
     throwing(false),

js/src/jscntxt.h

@@ -266,6 +266,9 @@ struct ThreadSafeContext : ContextFriendFields,
         return runtime_->onOutOfMemory(p, nbytes, maybeJSContext());
     }
 
+    /* Clear the pending exception (if any) due to OOM. */
+    void recoverFromOutOfMemory();
+
     inline void updateMallocCounter(size_t nbytes) {
         // Note: this is racy.
         runtime_->updateMallocCounter(zone_, nbytes);

js/src/jsobj.cpp

@@ -3055,8 +3055,9 @@ ReallocateElements(ThreadSafeContext *cx, JSObject *obj, ObjectElements *oldHead
 {
 #ifdef JSGC_GENERATIONAL
     if (cx->isJSContext()) {
-        return cx->asJSContext()->runtime()-> gcNursery.reallocateElements(cx->asJSContext(), obj, oldHeader,
-                                                                           oldCount, newCount);
+        return cx->asJSContext()->runtime()->gcNursery.reallocateElements(cx->asJSContext(), obj,
+                                                                          oldHeader, oldCount,
+                                                                          newCount);
     }
 #endif
 
@@ -3140,7 +3141,7 @@ JSObject::shrinkElements(ThreadSafeContext *cx, uint32_t newcap)
     uint32_t oldcap = getDenseCapacity();
     JS_ASSERT(newcap <= oldcap);
 
-    /* Don't shrink elements below the minimum capacity. */
+    // Don't shrink elements below the minimum capacity.
     if (oldcap <= SLOT_CAPACITY_MIN || !hasDynamicElements())
         return;
 
@@ -3151,8 +3152,10 @@ JSObject::shrinkElements(ThreadSafeContext *cx, uint32_t newcap)
 
     ObjectElements *newheader = ReallocateElements(cx, this, getElementsHeader(),
                                                    oldAllocated, newAllocated);
-    if (!newheader)
-        return;  /* Leave elements at its old size. */
+    if (!newheader) {
+        cx->recoverFromOutOfMemory();
+        return;  // Leave elements at its old size.
+    }
 
     newheader->capacity = newcap;
     elements = newheader->elements();