Dune. Modify (executable) based on cli arg or env var

Ecosystem
1

Hello.
I’d like to add (modes (byte exe)) to (executable) section of “dune” file if an environment variable is set or command line argument is provided.
However I couldn’t find anything related in the dune manual. Is it even possible?

Solution:
Run

dune build path/to/executable.bc

instead of

dune build path/to/executable.exe
1 Like
2

That’s not possible directly. Can you describe a bit more why you need to switch (modes) in this way?

3

By default we build native binary (for release, for ci and for development). But sometimes I need to switch to bytecode for interactive debugging.

4

dune knows about both types of executable without the need to change (modes): you can run dune build path/to/my_executable.bc to build a bytecode version (where you would put dune build path/to/my_executable.exe).

Would that work for your use case?

EDIT: bc not byte!

5

Unfortunately that doesn’t work for me. I get “Error: Don’t know how to build path/to/my_executable.byte” while “dune build path/to/my_executable.exe” is built successfully.

6

dune uses .bc not .byte

Gaëtan Gilbert

7

Yep, that works.
Thanks, @emillon and @SkySkimmer !

8

Hm. That seems to be different than specifying “(modes (byte exe))” in dune file.
With “dune build path/my_executable.bc” I get following error:

Error: Error on dynamically loaded library: ./libs/extc/dllextc_stubs.so: ./libs/extc/dllextc_stubs.so: undefined symbol: inflate

“extc” is a library with its own “dune” file defined like this:

(include_subdirs no)

(library
	(name extc)
	(libraries extlib)
	(c_names extc_stubs)
	(modules extc)
	(wrapped false)
)

(library
	(name extproc)
	(c_names process_stubs)
	(modules process)
	(wrapped false)
)
9

Yes, thanks! Too many years with ocamlbuild :slight_smile: