Everytime I run: G_DEBUG=resident-modules valgrind --tool=memcheck --leak-check=full --leak-resolution=high --num-callers=20 --log-file=vgdump --trace-children=yes WebKitBuild/Release/bin/MiniBrowser http://igalia.com the WebProcess crashes with SIGSEGV: ==5527== Invalid write of size 4 ==5527== at 0x5CD2594: WTFCrash (Assertions.cpp:333) ==5527== by 0x5A96C8F: JSC::linkFor(JSC::ExecState*, JSC::CallLinkInfo&, JSC::CodeBlock*, JSC::JSFunction*, JSC::MacroAssemblerCodePtr, JSC::CodeSpecializationKind, JSC::RegisterPreservat$ ==5527== by 0x5A7F55F: linkFor (JITOperations.cpp:717) ==5527== by 0x5A78F25: operationLinkCall (JITOperations.cpp:723) ==5527== by 0x39FE1A55: ??? ==5527== by 0x79FDD8FD: ??? ==5527== by 0x5CBAAE8: ??? (in /home/elima/gnome3/checkout/WebKit/WebKitBuild/Debug/lib/libjavascriptcoregtk-3.0.so.0.16.2) ==5527== by 0x39FE19F9: ??? ==5527== by 0x39FE19F9: ??? ==5527== by 0x5CB4F20: ??? (in /home/elima/gnome3/checkout/WebKit/WebKitBuild/Debug/lib/libjavascriptcoregtk-3.0.so.0.16.2) ==5527== by 0x5A6B2A4: JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) (JITCode.cpp:47) ==5527== by 0x5A4C605: JSC::Interpreter::execute(JSC::ProgramExecutable*, JSC::ExecState*, JSC::JSObject*) (Interpreter.cpp:933) ==5527== by 0x5B6AD2A: JSC::evaluate(JSC::ExecState*, JSC::SourceCode const&, JSC::JSValue, JSC::JSValue*) (Completion.cpp:82) ==5527== by 0xA9277E4: WebCore::JSMainThreadExecState::evaluate(JSC::ExecState*, JSC::SourceCode const&, JSC::JSValue, JSC::JSValue*) (JSMainThreadExecState.h:62) ==5527== by 0xA964FF4: WebCore::ScriptController::evaluateInWorld(WebCore::ScriptSourceCode const&, WebCore::DOMWrapperWorld&) (ScriptController.cpp:149) ==5527== by 0xA965111: WebCore::ScriptController::evaluate(WebCore::ScriptSourceCode const&) (ScriptController.cpp:165) ==5527== by 0xAC677DC: WebCore::ScriptElement::executeScript(WebCore::ScriptSourceCode const&) (ScriptElement.cpp:307) ==5527== by 0xAEBD29B: WebCore::HTMLScriptRunner::executePendingScriptAndDispatchEvent(WebCore::PendingScript&) (HTMLScriptRunner.cpp:144) ==5527== by 0xAEBD0E9: WebCore::HTMLScriptRunner::executeParsingBlockingScript() (HTMLScriptRunner.cpp:120) ==5527== by 0xAEBD5C7: WebCore::HTMLScriptRunner::executeParsingBlockingScripts() (HTMLScriptRunner.cpp:195) ==5527== Address 0xbbadbeef is not stack'd, malloc'd or (recently) free'd It happens in both release and debug builds, for trunk as of revision 167712. These crashes make it almost impossible to debug any other issue in WKGtk.