Lukasz Stafiniak

Debugging and Profiling OCaml – lessons (re)learned

Links

• OCaml.org tutorial on debugging
• ppx_minidebug, a debugging and logging framework.
• Debugging Native Code Binaries in Real World OCaml
• KC Sivaramakrishnan’s Getting Started with GDB on OCaml
  • Deterministically debugging concurrent GC bugs with rr
  • 15 minutes tutorial of GDB
• Javier Chávarri’s Profiling Dune Builds – a brief coverage of perf and memtrace
• vg-b’s workaround for some perf problems (the need for ocaml-option-fp)
• Tianyi Song’s Profiling OCaml programs the quick and dirty way about using Landmarks. Has precise timing (CPU cycles), both manual and automatic annotation (PPX based), callgraph visualization.
• Debugging OCaml with Emacs – setting up bytecode and native debugging.

Don’t forget

• Use Valgrind to debug memory corruption.
  • Symptoms: random crashes in garbage collection, in ctypes code, in system libraries etc.
  • Example invocation: valgrind --leak-check=full --leak-resolution=high --show-leak-kinds=all --errors-for-leak-kinds=none _build/default/bin/example.exe
• Use GDB when the program hangs to quickly see the stack trace.
• If you use landmarks to compare performances of parts within a program run: it seems that the optional wallclock timer is not reset properly between restarts.