ocamlbuild produces a blank archive file rather than an executable

Question

Working on a Debian-based Linux distro (PopOS), I have a folder of files and a Makefile containing

MODULES=move score main draw setup
OBJECTS=$(MODULES:=.cmo)
TEST=test.byte
OCAMLBUILD=ocamlbuild -use-ocamlfind
MAIN=main.byte

# Recipes 
default: build #first build (dependies) then run utop (command)
    utop

build: 
    $(OCAMLBUILD) $(OBJECTS) 

test:
    $(OCAMLBUILD) -tag 'debug' $(TEST) && ./$(TEST)

play:
    $(OCAMLBUILD) $(MAIN) && ./$(MAIN)

clean:
    ocamlbuild -clean

When I call make build it seems to work just fine, but the resulting .byte files don't run. In the terminal they show up in red, which indicates that the computer is understanding them to be archive files rather than executables. When I try to run ./main.byte it says the file cannot be found even though the file is listed in the directory.

Moreover, when I build this on a Mac it works just fine. It builds the program and runs it correctly.

Any thoughts about what this could be?

Answer 1

I'm not fully sure why this works on a Mac but not my Linux machine, but I did manage to play with this enough to get a solution. If I change the Makefile to be

MODULES=move score main draw setup
OBJECTS=$(MODULES:=.cmo)
TEST=test.byte
OCAMLBUILD=ocamlbuild -use-ocamlfind
MAIN=main.byte


default: build 
    utop

build: 
    $(OCAMLBUILD) $(OBJECTS) $(MAIN)

test:
    $(OCAMLBUILD) -tag 'debug' $(TEST) && ./$(TEST)

play:
    $(OCAMLBUILD) $(MAIN) && ./$(MAIN)

clean:
    ocamlbuild -clean

then the computer recognizes the executable.

Answer 2

In your original Makefile, make build does not run the command ocamlbuild $(MAIN) which should create the bytecode executable. You have to run make play for the bytecode executable to be built. In the modified Makefile, you included $(MAIN) in the list of targets passed to ocamlbuild in your build Makefile target, so now it is built by make build .