Debugging

neocaml integrates with dape (a DAP client, available from GNU ELPA) and ocamlearlybird for OCaml debugging. When dape is loaded, neocaml automatically registers its modes with dape's built-in ocamlearlybird configuration.

Setup

1. Install ocamlearlybird:

opam install earlybird

1. Install dape from GNU ELPA (M-x package-install RET dape RET).

2. Compile your program as bytecode. In your dune file:

(executable
 (name main)
 (modes byte exe))

1. Build with dune build.

Usage

Set breakpoints with M-x dape-breakpoint-toggle (or C-x C-a b) on the lines where you want execution to pause. Then start a debug session with M-x dape -- it will offer the ocamlearlybird config and guess the program path based on your current buffer name (e.g., _build/default/bin/main.bc). You can edit the path in the minibuffer if needed.

Once the session starts, dape provides the standard debugging commands:

Command	Keybinding	Description
dape-next	C-x C-a n	Step over
dape-step-in	C-x C-a i	Step into
dape-step-out	C-x C-a o	Step out
dape-continue	C-x C-a c	Continue execution
dape-breakpoint-toggle	C-x C-a b	Toggle breakpoint at point
dape-info		Show debugger info (variables, stack, breakpoints)
dape-repl		Open the debug REPL
dape-quit	C-x C-a q	Stop the debug session

Caveats

• ocamlearlybird only works with bytecode (.bc) executables, not native code.
• For dune >= 3.0, you may need to add (map_workspace_root false) to your dune-project for breakpoints to resolve correctly.
• See the ocamlearlybird documentation for troubleshooting and known limitations.
• neocaml normally offers to redirect you away from _build/ files. If this interferes with your debugging workflow, disable it:

(setq neocaml-redirect-build-files nil)