Bug 241538

we found a crash on our crash report system. we didn't reproduce it. from our system, we found serveral features below: first, it may happened much times on one device; second, it may happened on low-memory device. finally, it may happened related to webview and react-native. Thread 0（crashed） 1 JavaScriptCore WTF::StringImpl::hashSlowCase() const (in JavaScriptCore) + 132 2 JavaScriptCore WTF::HashTable<WTF::Packed<WTF::StringImpl*>, WTF::Packed<WTF::StringImpl*>, WTF::IdentityExtractor, WTF::DefaultHash<WTF::Packed<WTF::StringImpl*> >, WTF::HashTraits<WTF::Packed<WTF::StringImpl*> >, WTF::HashTraits<WTF::Packed<WTF::StringImpl*> > >::rehash(unsigned int, WTF::Packed<WTF::StringImpl*>*) (in JavaScriptCore) + 308 3 JavaScriptCore WTF::AtomStringImpl::remove(WTF::AtomStringImpl*) (in JavaScriptCore) + 448 4 JavaScriptCore WTF::StringImpl::~StringImpl() (in JavaScriptCore) + 76 5 JavaScriptCore JSC::Structure::destroy(JSC::JSCell*) (in JavaScriptCore) + 104 6 JavaScriptCore JSC::HeapCellType::finishSweep(JSC::MarkedBlock::Handle&, JSC::FreeList*) const (in JavaScriptCore) + 5540 7 JavaScriptCore JSC::MarkedBlock::Handle::sweep(JSC::FreeList*) (in JavaScriptCore) + 1164 8 JavaScriptCore JSC::MarkedSpace::lastChanceToFinalize() (in JavaScriptCore) + 136 9 JavaScriptCore JSC::Heap::lastChanceToFinalize() (in JavaScriptCore) + 372 10 JavaScriptCore JSC::VM::~VM() (in JavaScriptCore) + 656 11 JavaScriptCore JSC::JSLockHolder::~JSLockHolder() (in JavaScriptCore) + 316 12 JavaScriptCore -[JSVirtualMachine dealloc] (in JavaScriptCore) + 84 13 libobjc.A.dylib object_cxxDestructFromClass(objc_object*, objc_class*) (in libobjc.A.dylib) + 116 14 libobjc.A.dylib objc_destructInstance (in libobjc.A.dylib) + 80 15 libobjc.A.dylib _objc_rootDealloc (in libobjc.A.dylib) + 80 16 JavaScriptCore -[JSContext dealloc] (in JavaScriptCore) + 76 17 JavaScriptCore -[JSValue dealloc] (in JavaScriptCore) + 148 18 libobjc.A.dylib AutoreleasePoolPage::releaseUntil(objc_object**) (in libobjc.A.dylib) + 196 19 libobjc.A.dylib objc_autoreleasePoolPop (in libobjc.A.dylib) + 256 20 CoreFoundation _CFAutoreleasePoolPop (in CoreFoundation) + 32 21 CoreFoundation __CFRunLoopPerCalloutARPEnd (in CoreFoundation) + 48 22 CoreFoundation __CFRunLoopRun (in CoreFoundation) + 2076 23 CoreFoundation CFRunLoopRunSpecific (in CoreFoundation) + 612 24 GraphicsServices GSEventRunModal (in GraphicsServices) + 164 25 UIKitCore -[UIApplication _run] (in UIKitCore) + 888 26 UIKitCore UIApplicationMain (in UIKitCore) + 340 27 OurAppication main (in JD4iPhone) (main.m:15)