Experience report: hangs forever when trying to run `clang-repl`

[jeaye]

Hey folks. Vassil suggested I try idd when looking for a regression in clang-repl. I was unable to get it working, since idd would hang forever when I try to run the binaries. Both of them work just fine when running them with gdb individually.

The setup

~/projects/third-party/idd on main took 19ms at 11:57:20
❯ nix-shell -p python3 gdb

via λ (shell) ~/projects/third-party/idd on main took 194ms at 11:57:26
❯ python3 -m venv iddenv

via λ (shell) ~/projects/third-party/idd on main took 1s545ms at 11:57:31
❯ source iddenv/bin/activate

via λ (shell) ~/projects/third-party/idd on main took 27ms at 11:57:33
❯ python -m idd -c gdb -ba ~/projects/third-party/llvm-base/build/bin/clang-repl -ra ~/projects/third-party/llvm/build/bin/clang-repl

Setting a breakpoint

Notice that only the base gets any output here.

Running

Again, only the base has output, but neither actually hits the breakpoint.

Stuck

At this point, idd is stuck. If I try to quit, idd freezes. If I kill the process manually, the terminal is stuck in a bad state. Ultimately, I ended up manually debugging the two side by side, which worked well. So I'm not stuck on this anymore, but it's still an issue, or perhaps a set of issues.

Maybe interesting note

clang-repl reads from stdin, and I'm not sure how idd handles that. However, I don't think we even made it there, since my breakpoint was never triggered and we never saw the clang-repl > prompt.

Environment

• NixOS x86_64
• Python 3.12.10
• GDB 16.2

[mvassilev]

Hi @jeaye thanks for the report.
I will try to reproduce it with clang-repl and report back.