[jsc-dev] Crashing on iOS 9

shuan zhao hszhsh at icloud.com
Mon Feb 6 00:26:45 PST 2017 

I didn’t modify JSC, and I didn’t try linking against system’s JSC because TypedArray is not supported until iOS 10, which is required in my project.

It seems to be hard to reproduce the crash in a smaller test case. I’ll export my project and send you off-list later.

> On 6 Feb 2017, at 12:09 PM, Saam Barati <sbarati at apple.com> wrote:
> 
> If you're not able to get a smaller reduced test case, it'd be great if you can send me what you have and steps to reproduce. (You can send me the project off-list as well.) I've spent some time trying to reproduce a crash like this.
> 
> Are you linking your app against a modified JSC? Or does this crash happen when linking against the system's JSC as well?
> 
> - Saam
> 
> On Feb 5, 2017, at 7:58 PM, shuan zhao <hszhsh at icloud.com <mailto:hszhsh at icloud.com>> wrote:
> 
>> Thanks for your reply. I changed to a debug version of JSC build, and the stack looks a little different. It seems that source.provider()->source() became empty for some reason. The weird thing is that the crash did not happen when launched with “Malloc Scribble” or “Malloc Guard Edges” in Xcode.
>> 
>> My project is complicated, so it’s hard to say how to reproduce this. But I will try to reproduce the crash with a simplified project, and report the steps later.
>> 
>> 
>> #0	0x00000001017515e0 in ::WTFCrash() at /Users/hoolai/WebKit-GIT/Source/WTF/wtf/Assertions.cpp:379
>> #1	0x000000010162887c in std::__1::unique_ptr<JSC::FunctionNode, std::__1::default_delete<JSC::FunctionNode> > JSC::parse<JSC::FunctionNode>(JSC::VM*, JSC::SourceCode const&, JSC::Identifier const&, JSC::JSParserBuiltinMode, JSC::JSParserStrictMode, JSC::JSParserScriptMode, JSC::SourceParseMode, JSC::SuperBinding, JSC::ParserError&, JSC::JSTextPosition*, JSC::ConstructorKind, JSC::DerivedContextType, JSC::EvalContextType, JSC::DebuggerParseData*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/parser/Parser.h:1877
>> #2	0x0000000101627db8 in JSC::generateUnlinkedFunctionCodeBlock(JSC::VM&, JSC::UnlinkedFunctionExecutable*, JSC::SourceCode const&, JSC::CodeSpecializationKind, JSC::DebuggerMode, JSC::UnlinkedFunctionKind, JSC::ParserError&, JSC::SourceParseMode) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp:56
>> #3	0x0000000101627b80 in JSC::UnlinkedFunctionExecutable::unlinkedCodeBlockFor(JSC::VM&, JSC::SourceCode const&, JSC::CodeSpecializationKind, JSC::DebuggerMode, JSC::ParserError&, JSC::SourceParseMode) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp:210
>> #4	0x000000010157e2f0 in JSC::ScriptExecutable::newCodeBlockFor(JSC::CodeSpecializationKind, JSC::JSFunction*, JSC::JSScope*, JSC::JSObject*&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/ScriptExecutable.cpp:217
>> #5	0x000000010157f3cc in JSC::ScriptExecutable::prepareForExecutionImpl(JSC::VM&, JSC::JSFunction*, JSC::JSScope*, JSC::CodeSpecializationKind, JSC::CodeBlock*&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/ScriptExecutable.cpp:310
>> #6	0x0000000101130340 in JSC::JSObject* JSC::ScriptExecutable::prepareForExecution<JSC::FunctionExecutable>(JSC::VM&, JSC::JSFunction*, JSC::JSScope*, JSC::CodeSpecializationKind, JSC::CodeBlock*&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/bytecode/CodeBlock.h:1095
>> #7	0x00000001013711a0 in JSC::LLInt::setUpCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind, JSC::JSValue, JSC::LLIntCallLinkInfo*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1304
>> #8	0x00000001013703d4 in JSC::LLInt::genericCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1354
>> #9	0x00000001013702cc in ::llint_slow_path_call(JSC::ExecState *, JSC::Instruction *) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1361
>> #10	0x0000000101381ba0 in llint_entry ()
>> #11	0x0000000101381bb0 in llint_entry ()
>> #12	0x0000000101381bb0 in llint_entry ()
>> #13	0x000000010137b258 in llintPCRangeStart ()
>> #14	0x0000000101178864 in JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/jit/JITCode.cpp:81
>> #15	0x00000001011301d4 in JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/interpreter/Interpreter.cpp:927
>> #16	0x0000000100afa078 in JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/CallData.cpp:39
>> #17	0x0000000100afa16c in JSC::profiledCall(JSC::ExecState*, JSC::ProfilingReason, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/CallData.cpp:59
>> #18	0x000000010128003c in ::JSObjectCallAsFunction(JSContextRef, JSObjectRef, JSObjectRef, size_t, const JSValueRef *, JSValueRef *) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/API/JSObjectRef.cpp:563
>> 
>> 
>>> On 6 Feb 2017, at 1:36 AM, Geoffrey Garen <ggaren at apple.com <mailto:ggaren at apple.com>> wrote:
>>> 
>>> Hi Shuan.
>>> 
>>> The backtrace you included does not remind me of Bug 160337, but it does remind me of another crash that we’d like to diagnose and fix.
>>> 
>>> Do you think you could provide Saam instructions on how to reproduce this crash?
>>> 
>>> Thanks,
>>> Geoff
>>> 
>>>> On Feb 5, 2017, at 1:32 AM, shuan zhao <hszhsh at icloud.com <mailto:hszhsh at icloud.com>> wrote:
>>>> 
>>>> I’m running apps embedding my own build of JavaScriptCore on iOS (using C APIs only). It runs well on iOS 10 but crashes on iOS 9 or iOS 8. I guess it will also crash on iOS 7 or earlier systems which I have not tested on.
>>>> 
>>>> I found the bug (Bug 160337 <https://bugs.webkit.org/show_bug.cgi?id=160337> - Crash in JavaScriptCore GC when using JSC on dispatch queues (thread_get_state returns NULL stack pointer)). But my case is totally different because I have never got null stack pointer from thread_get_state. And I found that when launched with the option “Malloc Scribble” or “Malloc Guard Edges” checked in Xcode, my app won’t crash any more.
>>>> 
>>>> I have no idea what causes this crash. It would be very nice of you if you would give me some hints on the issue.
>>>> 
>>>> Mostly the crash stack was as follows, but sometimes it was different. And sometimes it reported errors that should not exist and crashed later.
>>>> 
>>>> #0	0x0000000100d66ca4 in JSC::Lexer<unsigned short>::setCode(JSC::SourceCode const&, JSC::ParserArena*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/parser/Lexer.cpp:571
>>>> #1	0x0000000100e037f8 in JSC::Parser<JSC::Lexer<unsigned short> >::Parser(JSC::VM*, JSC::SourceCode const&, JSC::JSParserBuiltinMode, JSC::JSParserStrictMode, JSC::JSParserScriptMode, JSC::SourceParseMode, JSC::SuperBinding, JSC::ConstructorKind, JSC::DerivedContextType, bool, JSC::EvalContextType, JSC::DebuggerParseData*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/parser/Parser.cpp:125
>>>> #2	0x0000000100e03c28 in JSC::Parser<JSC::Lexer<unsigned short> >::Parser(JSC::VM*, JSC::SourceCode const&, JSC::JSParserBuiltinMode, JSC::JSParserStrictMode, JSC::JSParserScriptMode, JSC::SourceParseMode, JSC::SuperBinding, JSC::ConstructorKind, JSC::DerivedContextType, bool, JSC::EvalContextType, JSC::DebuggerParseData*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/parser/Parser.cpp:123
>>>> #3	0x0000000100f3311c in std::__1::unique_ptr<JSC::FunctionNode, std::__1::default_delete<JSC::FunctionNode> > JSC::parse<JSC::FunctionNode>(JSC::VM*, JSC::SourceCode const&, JSC::Identifier const&, JSC::JSParserBuiltinMode, JSC::JSParserStrictMode, JSC::JSParserScriptMode, JSC::SourceParseMode, JSC::SuperBinding, JSC::ParserError&, JSC::JSTextPosition*, JSC::ConstructorKind, JSC::DerivedContextType, JSC::EvalContextType, JSC::DebuggerParseData*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/parser/Parser.h:1890
>>>> #4	0x0000000100f32b8c in JSC::generateUnlinkedFunctionCodeBlock(JSC::VM&, JSC::UnlinkedFunctionExecutable*, JSC::SourceCode const&, JSC::CodeSpecializationKind, JSC::DebuggerMode, JSC::UnlinkedFunctionKind, JSC::ParserError&, JSC::SourceParseMode) [inlined] at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp:56
>>>> #5	0x0000000100f32b4c in JSC::UnlinkedFunctionExecutable::unlinkedCodeBlockFor(JSC::VM&, JSC::SourceCode const&, JSC::CodeSpecializationKind, JSC::DebuggerMode, JSC::ParserError&, JSC::SourceParseMode) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp:210
>>>> #6	0x0000000100ee8518 in JSC::ScriptExecutable::newCodeBlockFor(JSC::CodeSpecializationKind, JSC::JSFunction*, JSC::JSScope*, JSC::JSObject*&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/ScriptExecutable.cpp:217
>>>> #7	0x0000000100ee8bc8 in JSC::ScriptExecutable::prepareForExecutionImpl(JSC::VM&, JSC::JSFunction*, JSC::JSScope*, JSC::CodeSpecializationKind, JSC::CodeBlock*&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/ScriptExecutable.cpp:310
>>>> #8	0x0000000100da0cd4 in JSC::JSObject* JSC::ScriptExecutable::prepareForExecution<JSC::FunctionExecutable>(JSC::VM&, JSC::JSFunction*, JSC::JSScope*, JSC::CodeSpecializationKind, JSC::CodeBlock*&) [inlined] at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/bytecode/CodeBlock.h:1095
>>>> #9	0x0000000100da0cbc in JSC::LLInt::setUpCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind, JSC::JSValue, JSC::LLIntCallLinkInfo*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1304
>>>> #10	0x0000000100daa270 in llint_entry ()
>>>> #11	0x0000000100da9e84 in llint_entry ()
>>>> #12	0x0000000100da9ee8 in llint_entry ()
>>>> #13	0x0000000100da35f8 in vmEntryToJavaScript ()
>>>> #14	0x0000000100c4defc in JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/jit/JITCode.cpp:81
>>>> #15	0x0000000100c20fc0 in JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/interpreter/Interpreter.cpp:927
>>>> #16	0x00000001008d8000 in JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) [inlined] at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/CallData.cpp:39
>>>> #17	0x00000001008d7fd0 in JSC::profiledCall(JSC::ExecState*, JSC::ProfilingReason, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/runtime/CallData.cpp:59
>>>> #18	0x0000000100cecb38 in ::JSObjectCallAsFunction(JSContextRef, JSObjectRef, JSObjectRef, size_t, const JSValueRef *, JSValueRef *) at /Users/hoolai/WebKit-GIT/Source/JavaScriptCore/API/JSObjectRef.cpp:563
>>>> 
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>>> 
>> 

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