VSCode does not hit breakpoints in V8 project

[zhuyingda]

I am newb to use CodeLLDB extension of VSCode, I try to debug v8 project by lldb.

Which OS: MacOS 11.6
Which extension version: 1.7.4
Which LLDB version: lldb-1300.0.42.3
Which VSCode version: 1.71.0

 Here is my configs:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "lldb-debug",
      "type": "lldb",
      "request": "launch",
      "program": "${workspaceFolder}/out/x64.debug/d8",
      "args": ["/path/to/foo.js"]
    }
  ]
}

The ${workspace} is in the path of V8 project, and I build the d8 by tools/dev/gm.py x64.debug.
After set breakpoints in source file in VSCode editor and run debugging, program exit with code 0 and without hit any breakpoint which I have just set.

I have read vscode-lldb/wiki/Breakpoints-are-not-getting-hit, dsymutil -s <binary> | grep N_OSO output these info:

dsymutil -s ./d8 | grep  N_OSO    
[     1] 000d9806 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/async-hooks-wrapper.o'
[  1425] 000e6a68 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/d8-console.o'
[  1914] 000ee9a8 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/d8-js.o'
[  1918] 000eea33 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/d8-platforms.o'
[  3268] 001030d2 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/d8-test.o'
[  4310] 00111be1 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/d8.o'
[ 15622] 001a9f56 66 (N_OSO        ) 03     0001   0000000000000000 '/path/to/v8_project/v8/out/x64.debug/obj/d8/d8-posix.o'

So, it seems that the binary file was compiled with debug symbols.

Also, when I use command-line lldb to debug, I breakpoint works fine:

lldb /path/to/v8_project/v8/out/x64.debug/d8 /path/to/foo.js
(lldb) target create "/path/to/v8_project/v8/out/x64.debug/d8"
Current executable set to '/path/to/v8_project/v8/out/x64.debug/d8' (x86_64).
(lldb) settings set -- target.run-args  "/path/to/foo.js"

(lldb) breakpoint set -f d8.cc -l 5499
Breakpoint 1: where = d8`v8::Shell::Main(int, char**) + 84 at d8.cc:5499:8, address = 0x00000001000570f4
(lldb) r
Process 50978 launched: '/path/to/v8_project/v8/out/x64.debug/d8' (x86_64)
Process 50978 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x00000001000570f4 d8`v8::Shell::Main(argc=2, argv=0x00007ffeefbff120) at d8.cc:5499:8

So, it seems like the binary file is debuggable for command-line lldb but not debuggable for our vscode-lldb tool?
Is there any tourbleshooting suggestion?

[vadimcn]

Please see this: https://github.com/vadimcn/vscode-lldb/wiki/Breakpoints-are-not-getting-hit

[zhuyingda]

Look for this: "Your build system or compiler rewrites source tree location..."

@vadimcn I also import v8/tools/lldb_commands.py to my ~/.lldbinit config, it does help for the command-line lldb. Should I add this config somehow into launch.json?

[vadimcn]

Please look at the header of the disassembly, it shows the source location emitted in debug info - ../../src/d8/d8.cc. You can try mapping ../.., but in my experience, this does not work well. But there's another option: since it's a relative path, it needs a base to be relative to. In CodeLLDB this will be the path set by relativePathBase (see https://github.com/vadimcn/vscode-lldb/blob/master/MANUAL.md#starting-a-new-debug-session). You can later that to point to the appropriate directory.

CodeLLDB does not process .lldbinit. You can achieve the same using initCommands.

[zhuyingda]

Please look at the header of the disassembly, it shows the source location emitted in debug info - ../../src/d8/d8.cc. You can try mapping ../..

Thank you so much, this has already solved my problem!
After changing previous config

"sourceMap": {
    ".": "${workspaceFolder}"
  }

to

"sourceMap": {
    "../..": "${workspaceFolder}"
  }

I can debug v8 project by CodeLLDB in VSCode. The breakpoint hit correctly.

[zhuyingda]

it shows the source location emitted in debug info - ../../src/d8/d8.cc.

One more question please, how do you get the debug info ? I have tried dsymutil and objdump, but not seen this ../../src/d8/d8.cc

[vadimcn]

The wiki page also suggests a couple of other methods, including show_debug_info debugger command.