"Step Over" hangs

[eloparco]

Hello, I followed the steps:

1. I cloned https://github.com/koush/quickjs and ran make qjs-debug
2. Installed the QuickJS Debugger extension from VS Code
3. I opened the quickjs repo in VS Code and, from the VS Code window, I did RUN AND DEBUG > Attach QuickJS
4. Finally, QUICKJS_DEBUG_ADDRESS=localhost:5555 ./qjs-debug test.js

I'm able to set the breakpoints in test.js, but if I keep pressing Step Over every once in a while it gets stuck. To get unstuck, I have to press Pause and then Step Over again.

Is that I known bug or am I doing anything wrong? Thanks

[eloparco]

If I attach with the debugger I can see that it hangs here https://github.com/koush/quickjs/blob/fe9aeaa703e3887866f3f32b217a27ee39b91268/quickjs-debugger-transport-unix.c#L29

Here is the stack trace:

thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x000000019ac6cacc libsystem_kernel.dylib`read + 8
    frame #1: 0x00000001000c3ca4 qjs-debug`js_transport_read(udata=0x0000000100206f90, buffer="00000081", length=9) at quickjs-debugger-transport-unix.c:29:19
    frame #2: 0x00000001000c1b00 qjs-debug`js_transport_read_fully(info=0x0000000100206558, buffer="00000081", length=9) at quickjs-debugger.c:16:24
    frame #3: 0x00000001000c08fc qjs-debug`js_process_debugger_messages(info=0x0000000100206558, cur_pc="!\xca\v\nLD\U00000002") at quickjs-debugger.c:443:14
    frame #4: 0x00000001000c1404 qjs-debug`js_debugger_check(ctx=0x0000000100405f00, cur_pc="!\xca\v\nLD\U00000002") at quickjs-debugger.c:669:9
    frame #5: 0x00000001000198f0 qjs-debug`JS_CallInternal(caller_ctx=0x0000000100405f00, func_obj=JSValue @ 0x000000016fdf7150, this_obj=JSValue @ 0x000000016fdf7140, new_target=JSValue @ 0x000000016fdf7130, argc=1, argv=0x000000016fdf7900, flags=0) at quickjs.c:16372:9
    frame #6: 0x000000010001b054 qjs-debug`JS_CallInternal(caller_ctx=0x0000000100405f00, func_obj=JSValue @ 0x000000016fdf9530, this_obj=JSValue @ 0x000000016fdf9520, new_target=JSValue @ 0x000000016fdf9510, argc=0, argv=0x000000016fdf9ce0, flags=0) at quickjs.c:16670:27
    frame #7: 0x000000010001b054 qjs-debug`JS_CallInternal(caller_ctx=0x0000000100405f00, func_obj=JSValue @ 0x000000016fdfb900, this_obj=JSValue @ 0x000000016fdfb8f0, new_target=JSValue @ 0x000000016fdfb8e0, argc=0, argv=0x000000016fdfc0d0, flags=0) at quickjs.c:16670:27
    frame #8: 0x000000010001b348 qjs-debug`JS_CallInternal(caller_ctx=0x0000000100405f00, func_obj=JSValue @ 0x000000016fdfdce0, this_obj=JSValue @ 0x000000016fdfdcd0, new_target=JSValue @ 0x000000016fdfdcc0, argc=0, argv=0x0000000000000000, flags=2) at quickjs.c:16706:27
    frame #9: 0x000000010000e354 qjs-debug`JS_CallFree(ctx=0x0000000100405f00, func_obj=JSValue @ 0x000000016fdfe4b0, this_obj=JSValue @ 0x000000016fdfe4a0, argc=0, argv=0x0000000000000000) at quickjs.c:18750:19
    frame #10: 0x000000010004f1c8 qjs-debug`js_evaluate_module(ctx=0x0000000100405f00, m=0x0000000100510b60) at quickjs.c:28361:19
    frame #11: 0x000000010002576c qjs-debug`JS_EvalFunctionInternal(ctx=0x0000000100405f00, fun_obj=JSValue @ 0x000000016fdfe680, this_obj=JSValue @ 0x000000016fdfe670, var_refs=0x0000000000000000, sf=0x0000000000000000) at quickjs.c:33582:19
    frame #12: 0x0000000100025648 qjs-debug`JS_EvalFunction(ctx=0x0000000100405f00, fun_obj=JSValue @ 0x000000016fdfe6c0) at quickjs.c:33597:12
    frame #13: 0x0000000100002634 qjs-debug`eval_buf(ctx=0x0000000100405f00, buf=0x0000000100510770, buf_len=971, filename="test.js", eval_flags=1) at qjs.c:65:19
    frame #14: 0x00000001000027a8 qjs-debug`eval_file(ctx=0x0000000100405f00, filename="test.js", module=1) at qjs.c:100:11
    frame #15: 0x0000000100002228 qjs-debug`main(argc=2, argv=0x000000016fdfedd8) at qjs.c:522:17
    frame #16: 0x000000019a953f28 dyld`start + 2236

[eloparco]

I spent some time investigating, but I couldn't find much. I could only see that, when the debugger was getting stuck, it was because a StackTrace request was sent by vscode, but no following Scopes request was being made. And it seemed that quickjs was waiting on that one.

So I decided to try an older vscode version (I went to the one from October 2021) and there the problem doesn't appear. Not sure if that's a bug in the most recent vscode versions or the fact that this repo is using an old vscode-mock-debug template not compatible with newer versions of vscode (for instance, now the vscode module has been deprecated).