microsoft / microsoft/vscode-cpptools
debug server startup fails due to stdout buffering
Nobody has claimed this yet.
- Dominant language
- TypeScript
- Stars
- 6.2k
- Forks
- 1.7k
- Avg merge
- 14h 46m
- Merged PRs (30d)
- 61
Description
Issue Type: Bug
This is probably actually a problem in MIEngine.
I'm using the Arduino extension on macOS, and debugging with avarice and avr-gdb, but this problem also occurs if I configure a plain cppdbg instance in launch.json instead of using the Arduino extension's debugger.
If specifying a debug server to start, it apparently gets launched with pipes, not a pseudo-terminal. If it doesn't flush its stdout, then VS Code will probably never see its startup message, and therefore time out on starting it.
This category of bug seems to have been reported multiple times, usually without resolution, and usually by people working with gdb debug servers.
On macOS, there is a workaround of using /usr/bin/env as debugServerPath, and specifying STDBUF1=L with the rest of the debug server path and arguments.
Arguably, authors of debug servers should line-buffer or explicitly flush their status messages sent to stdout, but this is a subtle interaction that is unlikely to be reported or well-troubleshooted.
Extension version: 1.9.8
VS Code version: Code 1.67.2 (Universal) (c3511e6c69bb39013c4a4b7b9566ec1ca73fc4d5, 2022-05-17T18:20:57.384Z)
OS version: Darwin x64 19.6.0
Restricted Mode: No
System Info
| Item | Value |
|---|---|
| CPUs | Intel(R) Core(TM) i7-7920HQ CPU @ 3.10GHz (8 x 3100) |
| GPU Status | 2d_canvas: enabled canvas_oop_rasterization: disabled_off direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_renderer: enabled_on video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled |
| Load (avg) | 2, 2, 2 |
| Memory (System) | 16.00GB (0.08GB free) |
| Process Argv | --crash-reporter-id 8c334355-bde7-413a-8609-0fd7d4a582f2 |
| Screen Reader | no |
| VM | 22% |
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the failure with a cppdbg launch configuration using debugServerPath and a server that does not flush stdout; compare it with the /usr/bin/env and STDBUF1=L workaround. Trace the debug-server startup timeout and define done as reliably detecting the server's startup message when stdout is connected through pipes.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- arduino, cpp, macos
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 30/100