Bug 247695 - Many memory leaks in the simple Apple JavaScriptCore C API usage
Summary: Many memory leaks in the simple Apple JavaScriptCore C API usage
Status: RESOLVED WONTFIX
Alias: None
Product: WebKit
Classification: Unclassified
Component: JavaScriptCore (show other bugs)
Version: Safari 16
Hardware: Mac (Apple Silicon) macOS 12
: P2 Normal
Assignee: Nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2022-11-09 13:31 PST by Sergio
Modified: 2022-11-09 19:47 PST (History)
2 users (show)

See Also:

Attachments
Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Sergio 2022-11-09 13:31:12 PST 
The simple create/release code:

    #include <JavaScriptCore/JSContextRef.h>

    int main() {
      auto *global = JSGlobalContextCreate(nullptr);
      JSGlobalContextRelease(global);
    }

built with clang:

    clang++ -std=c++14 -g test.cc -framework JavaScriptCore

and run with the leaks instrumentation:

    leaks -atExit -- ./a.out

reports a lot of leaks:

Process 19039 is not debuggable. Due to security restrictions, leaks can only show or save contents of readonly memory of restricted processes.

Process:         a.out [19039]
Path:            /Users/USER/*/a.out
Load Address:    0x1001b4000
Identifier:      a.out
Version:         0
Code Type:       ARM64
Platform:        macOS
Parent Process:  leaks [19037]

Date/Time:       2022-11-09 14:29:12.962 -0700
Launch Time:     2022-11-09 14:29:12.435 -0700
OS Version:      macOS 12.6 (21G115)
Report Version:  7
Analysis Tool:   /Applications/Xcode.app/Contents/Developer/usr/bin/leaks
Analysis Tool Version:  Xcode 14.0.1 (14A400)
----

leaks Report Version: 4.0
Process 19039: 1012 nodes malloced for 68 KB
Process 19039: 110 leaks for 4400 total leaked bytes.

    110 (4.30K) << TOTAL >>
      1 (1.25K) ROOT LEAK: 0x11d820000 [1280]
      1 (64 bytes) ROOT LEAK: 0x11d804960 [64]
      1 (64 bytes) ROOT LEAK: 0x11d8049a0 [64]
      1 (64 bytes) ROOT LEAK: 0x11d8049e0 [64]
      1 (64 bytes) ROOT LEAK: 0x11d804a20 [64]
      1 (32 bytes) ROOT LEAK: 0x11d804020 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804040 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804060 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804080 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8040a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8040c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8040e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804100 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804120 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804140 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804160 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804180 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8041a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8041c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8041e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804200 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804220 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804240 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804260 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804280 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8042a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8042c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8042e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804300 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804320 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804340 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804360 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804380 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8043a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8043c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8043e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804400 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804420 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804440 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804460 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804480 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8044a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8044c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8044e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804500 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804520 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804540 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804560 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804580 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8045a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8045c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8045e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804600 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804620 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804640 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804660 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804680 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8046a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8046c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8046e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804700 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804720 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804740 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804760 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804780 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8047a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8047c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8047e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804800 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804820 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804840 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804860 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804880 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8048a0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8048c0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d8048e0 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804900 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804920 [32]
      1 (32 bytes) ROOT LEAK: 0x11d804940 [32]
      1 (16 bytes) ROOT LEAK: 0x1090040c0 [16]
      1 (16 bytes) ROOT LEAK: 0x109004110 [16]
      1 (16 bytes) ROOT LEAK: 0x109004140 [16]
      1 (16 bytes) ROOT LEAK: 0x109004170 [16]
      1 (16 bytes) ROOT LEAK: 0x1090041a0 [16]
      1 (16 bytes) ROOT LEAK: 0x1090041d0 [16]
      1 (16 bytes) ROOT LEAK: 0x109004200 [16]
      1 (16 bytes) ROOT LEAK: 0x109004230 [16]
      1 (16 bytes) ROOT LEAK: 0x109004260 [16]
      1 (16 bytes) ROOT LEAK: 0x109004290 [16]
      1 (16 bytes) ROOT LEAK: 0x1090042c0 [16]
      1 (16 bytes) ROOT LEAK: 0x1090042f0 [16]
      1 (16 bytes) ROOT LEAK: 0x109004320 [16]
      1 (16 bytes) ROOT LEAK: 0x109004350 [16]
      1 (16 bytes) ROOT LEAK: 0x109004380 [16]
      1 (16 bytes) ROOT LEAK: 0x1090043b0 [16]
      1 (16 bytes) ROOT LEAK: 0x1090043e0 [16]
      1 (16 bytes) ROOT LEAK: 0x109004410 [16]
      1 (16 bytes) ROOT LEAK: 0x109004440 [16]
      1 (16 bytes) ROOT LEAK: 0x109004470 [16]
      1 (16 bytes) ROOT LEAK: 0x1090044a0 [16]
      1 (16 bytes) ROOT LEAK: 0x1090044d0 [16]
      1 (16 bytes) ROOT LEAK: 0x109004500 [16]
      1 (16 bytes) ROOT LEAK: 0x109004510 [16]
      1 (16 bytes) ROOT LEAK: 0x109004520 [16]
      1 (16 bytes) ROOT LEAK: 0x109004530 [16]
      1 (16 bytes) ROOT LEAK: 0x109004540 [16]
      1 (16 bytes) ROOT LEAK: 0x1090045b0 [16]
      1 (16 bytes) ROOT LEAK: 0x1090045d0 [16]
      1 (16 bytes) ROOT LEAK: <WTF::Detail::CallableWrapper<JSC::VMTraps::SignalSender::initializeSignals()::'lambda'()::operator()() const::'lambda'(WTF::Signal, WTF::SigInfo&, __darwin_arm_thread_state64&), WTF::SignalAction, WTF::Signal, WTF::SigInfo&, __darwin_arm_thread_state64&> 0x1090045f0> [16]
      1 (16 bytes) ROOT LEAK: <WTF::Detail::CallableWrapper<JSC::Wasm::prepareFastMemory()::$_1::operator()() const::'lambda'(WTF::Signal, WTF::SigInfo&, __darwin_arm_thread_state64&), WTF::SignalAction, WTF::Signal, WTF::SigInfo&, __darwin_arm_thread_state64&> 0x109004600> [16]

Is it a bug? If it is not, how to properly finalize JavaScriptCore global context?
Comment 1 Alexey Proskuryakov 2022-11-09 17:49:28 PST 
This is likely not an actual issue. CC'ing some experts for an authoritative answer though.

- This app doesn't give garbage collection any time to run.

- JSC uses decorated pointers which leaks doesn't understand.
Comment 2 Sergio 2022-11-09 18:14:59 PST 
If I call JSGarbageCollect(), it does not change output:

    #include <JavaScriptCore/JSContextRef.h>

    int main() {
      auto *global = JSGlobalContextCreate(nullptr);
      JSGarbageCollect(global);
      JSGlobalContextRelease(global);
    }

I would like to know a proper JavaScriptCore shutdown.
Comment 3 Yusuke Suzuki 2022-11-09 19:47:59 PST 
Thanks for reporting.
This is not a real issue, the problem is that leaks tool cannot trace compact pointers.
So they are false positive.