It seems really weird that we'd hit Structure::dump() when just loading a web page. I have no extra logging enabled, and am not web inspecting. (lldb) bt * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 3.1 * frame #0: 0x000000011617c0db JavaScriptCore`JSC::Structure::dump(this=0x00000001284f8380, out=0x00007ffeefbfaf28) const at Structure.cpp:1171 frame #1: 0x000000011617c6aa JavaScriptCore`JSC::Structure::dumpInContext(this=0x00000001284f8380, out=0x00007ffeefbfaf28, context=0x0000000000000000) const at Structure.cpp:1214 frame #2: 0x0000000115309d57 JavaScriptCore`WTF::ValueInContext<JSC::Structure, JSC::DumpContext>::dump(this=0x00007ffeefbfaa90, out=0x00007ffeefbfaf28) const at PrintStream.h:218 frame #3: 0x0000000115309d1d JavaScriptCore`void WTF::printInternal<WTF::ValueInContext<JSC::Structure, JSC::DumpContext> >(out=0x00007ffeefbfaf28, value=0x00007ffeefbfaa90) at PrintStream.h:130 frame #4: 0x0000000115fdf548 JavaScriptCore`void WTF::PrintStream::printImpl<WTF::ValueInContext<JSC::Structure, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfaf28, value=0x00007ffeefbfaa90, remainingValues=<no value available>) [2]) at PrintStream.h:89 frame #5: 0x0000000115fdf50d JavaScriptCore`void WTF::PrintStream::printImpl<char [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfaf28, value=<no value available>, remainingValues=0x00007ffeefbfaa90, remainingValues=<no value available>) [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext> const&, char const (&) [2]) at PrintStream.h:90 frame #6: 0x0000000115fdf4bb JavaScriptCore`void WTF::PrintStream::print<char [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfa988, out=0x00007ffeefbfaf28) [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext> const&, char const (&) [2])::'lambda'(WTF::PrintStream&)::operator()(WTF::PrintStream&) const at PrintStream.h:73 frame #7: 0x0000000115fdf475 JavaScriptCore`void WTF::PrintStream::atomically<void WTF::PrintStream::print<char [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext>, char [2]>(char const (&) [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext> const&, char const (&) [2])::'lambda'(WTF::PrintStream&)>(this=0x00007ffeefbfaf28, func=0x00007ffeefbfa988) [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext> const&, char const (&) [2])::'lambda'(WTF::PrintStream&) const&) at PrintStream.h:64 frame #8: 0x0000000115fda560 JavaScriptCore`void WTF::PrintStream::print<char [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfaf28, values=<no value available>, values=0x00007ffeefbfaa90, values=<no value available>) [13], WTF::ValueInContext<JSC::Structure, JSC::DumpContext> const&, char const (&) [2]) at PrintStream.h:71 frame #9: 0x0000000115fda1b7 JavaScriptCore`JSC::JSValue::dumpInContextAssumingStructure(this=0x00007ffeefbfad20, out=0x00007ffeefbfaf28, context=0x0000000000000000, structure=0x00000001284f8380) const at JSCJSValue.cpp:282 frame #10: 0x0000000115fd9d36 JavaScriptCore`JSC::JSValue::dumpInContext(this=0x00007ffeefbfad20, out=0x00007ffeefbfaf28, context=0x0000000000000000) const at JSCJSValue.cpp:236 frame #11: 0x00000001152d8cc7 JavaScriptCore`WTF::ValueInContext<JSC::JSValue, JSC::DumpContext>::dump(this=0x00007ffeefbfad28, out=0x00007ffeefbfaf28) const at PrintStream.h:218 frame #12: 0x00000001152d8c8d JavaScriptCore`void WTF::printInternal<WTF::ValueInContext<JSC::JSValue, JSC::DumpContext> >(out=0x00007ffeefbfaf28, value=0x00007ffeefbfad28) at PrintStream.h:130 frame #13: 0x00000001152e4b60 JavaScriptCore`void WTF::PrintStream::printImpl<WTF::ValueInContext<JSC::JSValue, JSC::DumpContext>, char [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfaf28, value=0x00007ffeefbfad28, remainingValues=<no value available>, remainingValues=0x00007ffeefbfad10, remainingValues=<no value available>) [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext> const&, char const (&) [2]) at PrintStream.h:89 frame #14: 0x00000001152e4b1d JavaScriptCore`void WTF::PrintStream::printImpl<char [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext>, char [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfaf28, value=<no value available>, remainingValues=0x00007ffeefbfad28, remainingValues=<no value available>, remainingValues=0x00007ffeefbfad10, remainingValues=<no value available>) [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext> const&, char const (&) [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext> const&, char const (&) [2]) at PrintStream.h:90 frame #15: 0x00000001152e4ac3 JavaScriptCore`void WTF::PrintStream::print<char [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext>, char [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfac88, out=0x00007ffeefbfaf28) [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext> const&, char const (&) [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext> const&, char const (&) [2])::'lambda'(WTF::PrintStream&)::operator()(WTF::PrintStream&) const at PrintStream.h:73 frame #16: 0x00000001152e4a75 JavaScriptCore`void WTF::PrintStream::atomically<void WTF::PrintStream::print<char [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext>, char [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext>, char [2]>(char const (&) [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext> const&, char const (&) [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext> const&, char const (&) [2])::'lambda'(WTF::PrintStream&)>(this=0x00007ffeefbfaf28, func=0x00007ffeefbfac88) [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext> const&, char const (&) [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext> const&, char const (&) [2])::'lambda'(WTF::PrintStream&) const&) at PrintStream.h:64 frame #17: 0x00000001152dcee8 JavaScriptCore`void WTF::PrintStream::print<char [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext>, char [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext>, char [2]>(this=0x00007ffeefbfaf28, values=<no value available>, values=0x00007ffeefbfad28, values=<no value available>, values=0x00007ffeefbfad10, values=<no value available>) [2], WTF::ValueInContext<JSC::JSValue, JSC::DumpContext> const&, char const (&) [3], WTF::ValueInContext<JSC::PropertyCondition, JSC::DumpContext> const&, char const (&) [2]) at PrintStream.h:71 frame #18: 0x00000001152dce51 JavaScriptCore`JSC::ObjectPropertyCondition::dumpInContext(this=0x00000001cdc36938, out=0x00007ffeefbfaf28, context=0x0000000000000000) const at ObjectPropertyCondition.cpp:41 frame #19: 0x00000001152dcf41 JavaScriptCore`JSC::ObjectPropertyCondition::dump(this=0x00000001cdc36938, out=0x00007ffeefbfaf28) const at ObjectPropertyCondition.cpp:46 frame #20: 0x000000011522582d JavaScriptCore`void WTF::printInternal<JSC::ObjectPropertyCondition>(out=0x00007ffeefbfaf28, value=0x00000001cdc36938) at PrintStream.h:130 frame #21: 0x00000001153e62ec JavaScriptCore`void WTF::PrintStream::printImpl<JSC::ObjectPropertyCondition, char [10], JSC::FireDetail>(this=0x00007ffeefbfaf28, value=0x00000001cdc36938, remainingValues=<no value available>, remainingValues=0x00007ffeefbfb160) [10], JSC::FireDetail const&) at PrintStream.h:89 frame #22: 0x00000001153e62b5 JavaScriptCore`void WTF::PrintStream::printImpl<char [15], JSC::ObjectPropertyCondition, char [10], JSC::FireDetail>(this=0x00007ffeefbfaf28, value=<no value available>, remainingValues=0x00000001cdc36938, remainingValues=<no value available>, remainingValues=0x00007ffeefbfb160) [15], JSC::ObjectPropertyCondition const&, char const (&) [10], JSC::FireDetail const&) at PrintStream.h:90 frame #23: 0x00000001153e625f JavaScriptCore`void WTF::PrintStream::print<char [15], JSC::ObjectPropertyCondition, char [10], JSC::FireDetail>(this=0x00007ffeefbfae78, out=0x00007ffeefbfaf28) [15], JSC::ObjectPropertyCondition const&, char const (&) [10], JSC::FireDetail const&)::'lambda'(WTF::PrintStream&)::operator()(WTF::PrintStream&) const at PrintStream.h:73 frame #24: 0x00000001153e6215 JavaScriptCore`void WTF::PrintStream::atomically<void WTF::PrintStream::print<char [15], JSC::ObjectPropertyCondition, char [10], JSC::FireDetail>(char const (&) [15], JSC::ObjectPropertyCondition const&, char const (&) [10], JSC::FireDetail const&)::'lambda'(WTF::PrintStream&)>(this=0x00007ffeefbfaf28, func=0x00007ffeefbfae78) [15], JSC::ObjectPropertyCondition const&, char const (&) [10], JSC::FireDetail const&)::'lambda'(WTF::PrintStream&) const&) at PrintStream.h:64 frame #25: 0x00000001153e09dc JavaScriptCore`void WTF::PrintStream::print<char [15], JSC::ObjectPropertyCondition, char [10], JSC::FireDetail>(this=0x00007ffeefbfaf28, values=<no value available>, values=0x00000001cdc36938, values=<no value available>, values=0x00007ffeefbfb160) [15], JSC::ObjectPropertyCondition const&, char const (&) [10], JSC::FireDetail const&) at PrintStream.h:71 frame #26: 0x00000001153e0858 JavaScriptCore`JSC::DFG::AdaptiveInferredPropertyValueWatchpoint::handleFire(this=0x00000001cdc36930, detail=0x00007ffeefbfb160) at DFGAdaptiveInferredPropertyValueWatchpoint.cpp:50 frame #27: 0x000000011520333c JavaScriptCore`JSC::AdaptiveInferredPropertyValueWatchpointBase::fire(this=0x00000001cdc36930, detail=0x00007ffeefbfb160) at AdaptiveInferredPropertyValueWatchpointBase.cpp:68 frame #28: 0x0000000115203473 JavaScriptCore`JSC::AdaptiveInferredPropertyValueWatchpointBase::StructureWatchpoint::fireInternal(this=0x00000001cdc36958, detail=0x00007ffeefbfb160) at AdaptiveInferredPropertyValueWatchpointBase.cpp:82 frame #29: 0x0000000115322842 JavaScriptCore`JSC::Watchpoint::fire(this=0x00000001cdc36958, detail=0x00007ffeefbfb160) at Watchpoint.cpp:55 frame #30: 0x0000000115322e98 JavaScriptCore`JSC::WatchpointSet::fireAllWatchpoints(this=0x0000000194c64860, vm=0x0000000128000000, detail=0x00007ffeefbfb160) at Watchpoint.cpp:140 frame #31: 0x0000000115322cf4 JavaScriptCore`JSC::WatchpointSet::fireAllSlow(this=0x0000000194c64860, vm=0x0000000128000000, detail=0x00007ffeefbfb160) at Watchpoint.cpp:91 frame #32: 0x000000011618b803 JavaScriptCore`void JSC::WatchpointSet::fireAll<JSC::StructureFireDetail>(this=0x0000000194c64860, vm=0x0000000128000000, fireDetails=0x00007ffeefbfb160) at Watchpoint.h:160 frame #33: 0x000000011617b6ca JavaScriptCore`void JSC::InlineWatchpointSet::fireAll<JSC::StructureFireDetail>(this=0x00000001284f83e0, vm=0x0000000128000000, fireDetails=StructureFireDetail @ 0x00007ffeefbfb160) at Watchpoint.h:299 frame #34: 0x0000000116176765 JavaScriptCore`JSC::Structure::didTransitionFromThisStructure(this=0x00000001284f8380, deferred=0x0000000000000000) const at Structure.cpp:1073 frame #35: 0x000000011617638b JavaScriptCore`JSC::Structure::Structure(this=0x00000001bf4ebe20, vm=0x0000000128000000, previous=0x00000001284f8380, deferred=0x0000000000000000) at Structure.cpp:282 frame #36: 0x00000001161767cd JavaScriptCore`JSC::Structure::Structure(this=0x00000001bf4ebe20, vm=0x0000000128000000, previous=0x00000001284f8380, deferred=0x0000000000000000) at Structure.cpp:259 frame #37: 0x0000000116177f8c JavaScriptCore`JSC::Structure::create(vm=0x0000000128000000, previous=0x00000001284f8380, deferred=0x0000000000000000) at StructureInlines.h:57 frame #38: 0x00000001161786ab JavaScriptCore`JSC::Structure::toDictionaryTransition(vm=0x0000000128000000, structure=0x00000001284f8380, kind=UncachedDictionaryKind, deferred=0x0000000000000000) at Structure.cpp:597 frame #39: 0x00000001161782a6 JavaScriptCore`JSC::Structure::toUncacheableDictionaryTransition(vm=0x0000000128000000, structure=0x00000001284f8380) at Structure.cpp:616 frame #40: 0x0000000116178244 JavaScriptCore`JSC::Structure::removePropertyTransition(vm=0x0000000128000000, structure=0x00000001284f8380, propertyName=PropertyName @ 0x00007ffeefbfb378, offset=0x00007ffeefbfb3d4) at Structure.cpp:547 frame #41: 0x0000000116059533 JavaScriptCore`JSC::JSObject::deleteProperty(cell=0x000000012b814fb0, exec=0x00007ffeefbfb6f0, propertyName=PropertyName @ 0x00007ffeefbfb450) at JSObject.cpp:1916 frame #42: 0x0000000116090d15 JavaScriptCore`JSC::JSSymbolTableObject::deleteProperty(cell=0x000000012b814fb0, exec=0x00007ffeefbfb6f0, propertyName=PropertyName @ 0x00007ffeefbfb4a0) at JSSymbolTableObject.cpp:53 frame #43: 0x0000000106fa0b73 WebCore`WebCore::JSDOMWindow::deleteProperty(cell=0x000000012b814fb0, exec=0x00007ffeefbfb6f0, propertyName=PropertyName @ 0x00007ffeefbfb4f0) at JSDOMWindowCustom.cpp:318 frame #44: 0x000000011607cf8d JavaScriptCore`JSC::JSProxy::deleteProperty(cell=0x000000012b804000, exec=0x00007ffeefbfb6f0, propertyName=PropertyName @ 0x00007ffeefbfb548) at JSProxy.cpp:97 frame #45: 0x0000000115d76189 JavaScriptCore`::llint_slow_path_del_by_val(exec=0x00007ffeefbfb6f0, pc=0x000000013afdef80) at LLIntSlowPaths.cpp:1039 frame #46: 0x0000000114e425e4 JavaScriptCore`llint_entry at LowLevelInterpreter64.asm:58 frame #47: 0x0000020cef7db6dd frame #48: 0x0000020cef78c80c frame #49: 0x0000000114e43932 JavaScriptCore`llint_entry at LowLevelInterpreter.asm:851 frame #50: 0x0000000114e43932 JavaScriptCore`llint_entry at LowLevelInterpreter.asm:851 frame #51: 0x0000020cef85315e frame #52: 0x0000020cef89db22 frame #53: 0x0000000114e43932 JavaScriptCore`llint_entry at LowLevelInterpreter.asm:851 frame #54: 0x0000000114e43932 JavaScriptCore`llint_entry at LowLevelInterpreter.asm:851 frame #55: 0x0000000114e3b322 JavaScriptCore`vmEntryToJavaScript at LowLevelInterpreter64.asm:257 frame #56: 0x0000000115c9070a JavaScriptCore`JSC::JITCode::execute(this=0x00000001cdc635b0, vm=0x0000000128000000, protoCallFrame=0x00007ffeefbfbde0) at JITCodeInlines.h:38 frame #57: 0x0000000115c90ce3 JavaScriptCore`JSC::Interpreter::executeCall(this=0x0000000127800b00, callFrame=0x000000012b814ff8, function=0x0000000199b008d0, callType=JS, callData=0x00007ffeefbfc400, thisValue=JSValue @ 0x00007ffeefbfbef0, args=0x00007ffeefbfc2e0) at Interpreter.cpp:1023 frame #58: 0x0000000115f1ecda JavaScriptCore`JSC::call(exec=0x000000012b814ff8, functionObject=JSValue @ 0x00007ffeefbfbf70, callType=JS, callData=0x00007ffeefbfc400, thisValue=JSValue @ 0x00007ffeefbfbf68, args=0x00007ffeefbfc2e0) at CallData.cpp:41 frame #59: 0x0000000115f1edbc JavaScriptCore`JSC::call(exec=0x000000012b814ff8, functionObject=JSValue @ 0x00007ffeefbfc060, callType=JS, callData=0x00007ffeefbfc400, thisValue=JSValue @ 0x00007ffeefbfc058, args=0x00007ffeefbfc2e0, returnedException=0x00007ffeefbfc308) at CallData.cpp:48 frame #60: 0x0000000115f1f05d JavaScriptCore`JSC::profiledCall(exec=0x000000012b814ff8, reason=Other, functionObject=JSValue @ 0x00007ffeefbfc0f0, callType=JS, callData=0x00007ffeefbfc400, thisValue=JSValue @ 0x00007ffeefbfc0e8, args=0x00007ffeefbfc2e0, returnedException=0x00007ffeefbfc308) at CallData.cpp:67 frame #61: 0x0000000106f6c49b WebCore`WebCore::JSMainThreadExecState::profiledCall(exec=0x000000012b814ff8, reason=Other, functionObject=JSValue @ 0x00007ffeefbfc180, callType=JS, callData=0x00007ffeefbfc400, thisValue=JSValue @ 0x00007ffeefbfc178, args=0x00007ffeefbfc2e0, returnedException=0x00007ffeefbfc308) at JSMainThreadExecState.h:72 frame #62: 0x0000000106faf756 WebCore`WebCore::JSEventListener::handleEvent(this=0x000000012d5089f0, scriptExecutionContext=0x0000000152800000, event=0x00000001cdca0030) at JSEventListener.cpp:169 frame #63: 0x0000000107535822 WebCore`WebCore::EventTarget::fireEventListeners(this=0x0000000169100840, event=0x00000001cdca0030, listeners={ size = 1, capacity = 0 }) at EventTarget.cpp:292 frame #64: 0x000000010753163a WebCore`WebCore::EventTarget::fireEventListeners(this=0x0000000169100840, event=0x00000001cdca0030) at EventTarget.cpp:234 frame #65: 0x00000001075915f4 WebCore`WebCore::Node::handleLocalEvents(this=0x0000000169100840, event=0x00000001cdca0030) at Node.cpp:2321 frame #66: 0x0000000107518ebd WebCore`WebCore::EventContext::handleLocalEvents(this=0x00000001cdc9f810, event=0x00000001cdca0030) const at EventContext.cpp:54 frame #67: 0x000000010752d3c6 WebCore`WebCore::dispatchEventInDOM(event=0x00000001cdca0030, path=0x00007ffeefbfc7e8) at EventDispatcher.cpp:91 frame #68: 0x000000010752cef1 WebCore`WebCore::EventDispatcher::dispatchEvent(node=0x0000000169100840, event=0x00000001cdca0030) at EventDispatcher.cpp:159 frame #69: 0x000000010759164d WebCore`WebCore::Node::dispatchEvent(this=0x0000000169100840, event=0x00000001cdca0030) at Node.cpp:2331 frame #70: 0x00000001078e8b7e WebCore`WebCore::HTMLScriptElement::dispatchLoadEvent(this=0x0000000169100840) at HTMLScriptElement.cpp:179 frame #71: 0x00000001075ccbe0 WebCore`WebCore::ScriptElement::dispatchLoadEventRespectingUserGestureIndicator(this=0x0000000169100840) at ScriptElement.cpp:410 frame #72: 0x00000001075cce0b WebCore`WebCore::ScriptElement::executeScriptAndDispatchEvent(this=0x0000000169100840, loadableScript=0x000000012d508ab0) at ScriptElement.cpp:427 frame #73: 0x00000001075cced6 WebCore`WebCore::ScriptElement::executePendingScript(this=0x0000000169100840, pendingScript=0x000000012d508b80) at ScriptElement.cpp:434 frame #74: 0x00000001075e644b WebCore`WebCore::ScriptRunner::timerFired(this=0x00000001229212c0) at ScriptRunner.cpp:121 frame #75: 0x00000001075ffa91 WebCore`WTF::Function<void ()>::CallableWrapper<std::__1::__bind<void (WebCore::ScriptRunner::*&)(), WebCore::ScriptRunner*> >::call() [inlined] decltype(__f=0x0000000122921378, __a0=0x0000000122921388)).*fp(std::__1::forward<>(fp1))) std::__1::__invoke<void (WebCore::ScriptRunner::*&)(), WebCore::ScriptRunner*&, void>(void (WebCore::ScriptRunner::*&&&)(), WebCore::ScriptRunner*&&&) at type_traits:4264 frame #76: 0x00000001075ffa12 WebCore`WTF::Function<void ()>::CallableWrapper<std::__1::__bind<void (WebCore::ScriptRunner::*&)(), WebCore::ScriptRunner*> >::call() [inlined] std::__1::__bind_return<void (WebCore::ScriptRunner::*)(), std::__1::tuple<WebCore::ScriptRunner*>, std::__1::tuple<>, __is_valid_bind_return<void (WebCore::ScriptRunner::*)(), std::__1::tuple<WebCore::ScriptRunner*>, std::__1::tuple<> >::value>::type std::__1::__apply_functor<void (__f=0x0000000122921378, __bound_args=0x0000000122921388, __args=0x00007ffeefbfcc18)(), std::__1::tuple<WebCore::ScriptRunner*>, 0ul, std::__1::tuple<> >(void (WebCore::ScriptRunner::*&)(), std::__1::tuple<WebCore::ScriptRunner*>&, std::__1::__tuple_indices<0ul>, std::__1::tuple<>&&) at functional:2224 frame #77: 0x00000001075ff9e2 WebCore`WTF::Function<void ()>::CallableWrapper<std::__1::__bind<void (WebCore::ScriptRunner::*&)(), WebCore::ScriptRunner*> >::call() [inlined] std::__1::__bind_return<void (WebCore::ScriptRunner::*)(), std::__1::tuple<WebCore::ScriptRunner*>, std::__1::tuple<>, __is_valid_bind_return<void (WebCore::ScriptRunner::*)(), std::__1::tuple<WebCore::ScriptRunner*>, std::__1::tuple<> >::value>::type std::__1::__bind<void (this=0x0000000122921378)(), WebCore::ScriptRunner*>::operator()<>() at functional:2257 frame #78: 0x00000001075ff9bf WebCore`WTF::Function<void ()>::CallableWrapper<std::__1::__bind<void (this=0x0000000122921370)(), WebCore::ScriptRunner*> >::call() at Function.h:101 frame #79: 0x00000001056d0c0b WebCore`WTF::Function<void ()>::operator(this=0x0000000122921358)() const at Function.h:56 frame #80: 0x0000000105722a39 WebCore`WebCore::Timer::fired(this=0x0000000122921318) at Timer.h:131 frame #81: 0x0000000107fd9084 WebCore`WebCore::ThreadTimers::sharedTimerFiredInternal(this=0x0000000122908600) at ThreadTimers.cpp:117 frame #82: 0x0000000107feea01 WebCore`WebCore::ThreadTimers::setSharedTimer(this=0x0000000122908638)::$_0::operator()() const at ThreadTimers.cpp:69 frame #83: 0x0000000107fee9b9 WebCore`WTF::Function<void ()>::CallableWrapper<WebCore::ThreadTimers::setSharedTimer(this=0x0000000122908630)::$_0>::call() at Function.h:101 frame #84: 0x00000001056d0c0b WebCore`WTF::Function<void ()>::operator(this=0x000000010a237490)() const at Function.h:56 frame #85: 0x0000000107fb1205 WebCore`WebCore::MainThreadSharedTimer::fired(this=0x000000010a237488) at MainThreadSharedTimer.cpp:54 frame #86: 0x0000000108055079 WebCore`WebCore::timerFired((null)=0x0000614000160e40, (null)=0x0000000000000000) at MainThreadSharedTimerCF.cpp:74 frame #87: 0x00007fff56a38064 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20 frame #88: 0x00007fff56a37cd7 CoreFoundation`__CFRunLoopDoTimer + 1095 frame #89: 0x00007fff56a377da CoreFoundation`__CFRunLoopDoTimers + 346 frame #90: 0x00007fff56a2edab CoreFoundation`__CFRunLoopRun + 2427 frame #91: 0x00007fff56a2e1a3 CoreFoundation`CFRunLoopRunSpecific + 483 frame #92: 0x00007fff55d16d96 HIToolbox`RunCurrentEventLoopInMode + 286 frame #93: 0x00007fff55d16b06 HIToolbox`ReceiveNextEventCommon + 613 frame #94: 0x00007fff55d16884 HIToolbox`_BlockUntilNextEventMatchingListInModeWithFilter + 64 frame #95: 0x00007fff53fc9a73 AppKit`_DPSNextEvent + 2085 frame #96: 0x00007fff5475fe34 AppKit`-[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 3044 frame #97: 0x00007fff53fbe885 AppKit`-[NSApplication run] + 764 frame #98: 0x00007fff53f8da72 AppKit`NSApplicationMain + 804 frame #99: 0x0000000100005cc9 MiniBrowser`main(argc=5, argv=0x00007ffeefbff618) at main.m:32 frame #100: 0x00007fff7ed77015 libdyld.dylib`start + 1 frame #101: 0x00007fff7ed77015 libdyld.dylib`start + 1 (lldb)
Should DFG::AdaptiveInferredPropertyValueWatchpoint::handleFire() really be doing: StringPrintStream out; out.print("Adaptation of ", key(), " failed: ", detail);
This code path is responsible for a bunch of memory allocations: fastMalloc allocation 8718 1 0x114d8bcc1 WTF::fastMalloc(unsigned long) 2 0x114de71a4 WTF::StringPrintStream::increaseSize(unsigned long) 3 0x114de6fcd WTF::StringPrintStream::vprintf(char const*, __va_list_tag*) 4 0x114dc5ba0 WTF::PrintStream::printf(char const*, ...) 5 0x114dc5dc9 WTF::printInternal(WTF::PrintStream&, char const*) 6 0x114dc69b2 void WTF::PrintStream::printImpl<char const*>(char const* const&) 7 0x114dc6970 void WTF::PrintStream::print<char const*>(char const* const&)::'lambda'(WTF::PrintStream&)::operator()(WTF::PrintStream&) const 8 0x114dc6935 void WTF::PrintStream::atomically<void WTF::PrintStream::print<char const*>(char const* const&)::'lambda'(WTF::PrintStream&)>(void WTF::PrintStream::print<char const*>(char const* const&)::'lambda'(WTF::PrintStream&) const&) 9 0x114dc5f58 void WTF::PrintStream::print<char const*>(char const* const&) 10 0x114dc5f25 WTF::printInternal(WTF::PrintStream&, WTF::CString const&) 11 0x114dc681f void WTF::PrintStream::printImpl<WTF::CString>(WTF::CString const&) 12 0x114dc67e0 void WTF::PrintStream::print<WTF::CString>(WTF::CString const&)::'lambda'(WTF::PrintStream&)::operator()(WTF::PrintStream&) const 13 0x114dc67a5 void WTF::PrintStream::atomically<void WTF::PrintStream::print<WTF::CString>(WTF::CString const&)::'lambda'(WTF::PrintStream&)>(void WTF::PrintStream::print<WTF::CString>(WTF::CString const&)::'lambda'(WTF::PrintStream&) const&) 14 0x114dc64f8 void WTF::PrintStream::print<WTF::CString>(WTF::CString const&) 15 0x114dc5ec1 WTF::printExpectedCStringHelper(WTF::PrintStream&, char const*, std::experimental::fundamentals_v3::expected<WTF::CString, WTF::UTF8ConversionError>) 16 0x114dc600b WTF::printInternal(WTF::PrintStream&, WTF::StringImpl const*) 17 0x115222ce0 WTF::printInternal(WTF::PrintStream&, WTF::UniquedStringImpl const*) 18 0x115222c9d WTF::printInternal(WTF::PrintStream&, WTF::UniquedStringImpl*) 19 0x11618bcef void WTF::PrintStream::printImpl<WTF::UniquedStringImpl*, char [2], int>(WTF::UniquedStringImpl* const&, char const (&) [2], int const&) 20 0x11618bcb5 void WTF::PrintStream::printImpl<WTF::CommaPrinter, WTF::UniquedStringImpl*, char [2], int>(WTF::CommaPrinter const&, WTF::UniquedStringImpl* const&, char const (&) [2], int const&) 21 0x11618bc5f void WTF::PrintStream::print<WTF::CommaPrinter, WTF::UniquedStringImpl*, char [2], int>(WTF::CommaPrinter const&, WTF::UniquedStringImpl* const&, char const (&) [2], int const&)::'lambda'(WTF::PrintStream&)::operator()(WTF::PrintStream&) const 22 0x11618bc15 void WTF::PrintStream::atomically<void WTF::PrintStream::print<WTF::CommaPrinter, WTF::UniquedStringImpl*, char [2], int>(WTF::CommaPrinter const&, WTF::UniquedStringImpl* const&, char const (&) [2], int const&)::'lambda'(WTF::PrintStream&)>(void WTF::PrintStream::print<WTF::CommaPrinter, WTF::UniquedStringImpl*, char [2], int>(WTF::CommaPrinter const&, WTF::UniquedStringImpl* const&, char const (&) [2], int const&)::'lambda'(WTF::PrintStream&) const&) 23 0x11618bbcc void WTF::PrintStream::print<WTF::CommaPrinter, WTF::UniquedStringImpl*, char [2], int>(WTF::CommaPrinter const&, WTF::UniquedStringImpl* const&, char const (&) [2], int const&) 24 0x11618bb6b JSC::Structure::dump(WTF::PrintStream&) const::$_7::operator()(JSC::PropertyMapEntry const&) const 25 0x11617c45f void JSC::Structure::forEachPropertyConcurrently<JSC::Structure::dump(WTF::PrintStream&) const::$_7>(JSC::Structure::dump(WTF::PrintStream&) const::$_7 const&) 26 0x11617c150 JSC::Structure::dump(WTF::PrintStream&) const 27 0x11617c6aa JSC::Structure::dumpInContext(WTF::PrintStream&, JSC::DumpContext*) const 28 0x115309d57 WTF::ValueInContext<JSC::Structure, JSC::DumpContext>::dump(WTF::PrintStream&) const 29 0x115309d1d void WTF::printInternal<WTF::ValueInContext<JSC::Structure, JSC::DumpContext> >(WTF::PrintStream&, WTF::ValueInContext<JSC::Structure, JSC::DumpContext> const&)
These are the > 1024 byte allocations I see under this call stack: fastMalloc allocation 1080 fastMalloc allocation 2162 fastMalloc allocation 4354 fastMalloc allocation 8718 fastMalloc allocation 5461 fastMalloc allocation 1080 fastMalloc allocation 2162 fastMalloc allocation 4354 fastMalloc allocation 8718 fastMalloc allocation 5461 fastMalloc allocation 1080 fastMalloc allocation 2162 fastMalloc allocation 4354 fastMalloc allocation 8718 fastMalloc allocation 5461 That's a lot of memory churn for a string that no-one cares about.
<rdar://problem/40974404>
AdaptiveStructureWatchpoint::fireInternal() does this too.
And ArrayPrototypeAdaptiveInferredPropertyWatchpoint::handleFire()
Nice, yeah, creating these strings is a pure overhead if we do not dump watch point firing information.
Created attachment 342489 [details] Patch
Comment on attachment 342489 [details] Patch Rejecting attachment 342489 [details] from commit-queue. Number of test failures exceeded the failure limit. Full output: http://webkit-queues.webkit.org/results/8139751
Created attachment 342497 [details] Archive of layout-test-results from webkit-cq-02 for mac-sierra The attached test failures were seen while running run-webkit-tests on the commit-queue. Bot: webkit-cq-02 Port: mac-sierra Platform: Mac OS X 10.12.6
Ugh, none of those failures are probably relevant to my patch... That's what I get for using cq.
Committed r232738: <https://trac.webkit.org/changeset/232738>