difficulties on macos, arm64

[anentropic]

I had already brew install glfw

first attempt to opam instal glfw-ocaml failed with:

# File "glfw-ocaml/dune", line 9, characters 15-25:
# 9 |   (names       GLFW_stubs)
#                    ^^^^^^^^^^
# (cd _build/default/glfw-ocaml && /usr/bin/cc -O2 -fno-strict-aliasing -fwrapv -pthread -D_FILE_OFFSET_BITS=64 -O2 -fno-strict-aliasing -fwrapv -pthread -g -I /Users/paul/.opam/oktree/lib/ocaml -o GLFW_stubs.o -c GLFW_stubs.c)
# GLFW_stubs.c:1:10: fatal error: 'GLFW/glfw3.h' file not found
# #include <GLFW/glfw3.h>
#          ^~~~~~~~~~~~~~
# 1 error generated.

from this answer https://stackoverflow.com/a/67378304/202168 I fixed that by export CPATH=/opt/homebrew/include

installed successfully

then I copied the code from example window.ml and tried to compile it:

ocamlfind ocamlopt -package glfw-ocaml -thread -linkpkg -o glfw.native glfw.ml
File "glfw.ml", line 8, characters 15-32:
8 |   let window = GLFW.createWindow 640 480 "Hello World" () in
                   ^^^^^^^^^^^^^^^^^
Warning 6 [labels-omitted]: labels width, height, title were omitted in the application of this function.
File "glfw.ml", line 10, characters 2-25:
10 |   GLFW.makeContextCurrent (Some window);
       ^^^^^^^^^^^^^^^^^^^^^^^
Warning 6 [labels-omitted]: label window was omitted in the application of this function.
File "glfw.ml", line 12, characters 13-35:
12 |   while not (GLFW.windowShouldClose window) do
                  ^^^^^^^^^^^^^^^^^^^^^^
Warning 6 [labels-omitted]: label window was omitted in the application of this function.
File "glfw.ml", line 16, characters 4-20:
16 |     GLFW.swapBuffers window;
         ^^^^^^^^^^^^^^^^
Warning 6 [labels-omitted]: label window was omitted in the application of this function.
Undefined symbols for architecture arm64:
  "_caml_glClearColorBufferBit", referenced from:
      _camlGlfw__entry in glfw.o
      _camlGlfw__1 in glfw.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
File "caml_startup", line 1:
Error: Error during linking (exit code 1)

I found a couple of answers:

• https://stackoverflow.com/questions/70040725/glfw-3-3-5-undefined-symbols-for-architecture-arm64
• https://stackoverflow.com/questions/68871506/m1-clion-cmake-hit-an-error-when-using-glfw-glew-headfile

the solution there seems to revolve around having a CMakeLists.txt file with target_link_libraries(<project> glfw)

but I have no idea how to relate that back to glfw-ocaml ...do you have any tips? thank you!

[SylvainBoilard]

Hi,

The error you are getting is actually about a missing stub for the external function glClearColorBufferBit which is implemented in the window_stubs.c file. You should copy that file too and append window_stubs.c -cclib -lGL to your ocamlfind command line.

Alternatively the dune file present in that example folder shows how to create a window_stubs library from the C file and link it with an executable.

[anentropic]

Ah, thank you.

to understand the role of window_stubs.c in the example ... is that just to avoid depending on some ocaml opengl library?

so if e.g. I used lablgl I would not need an extra .c file?

[anentropic]

...and indeed, if I comment out the glClearColorBufferBit parts then I can compile the window.ml as I was trying before

and a window opens and works perfectly 👍

thanks again!

[SylvainBoilard]

to understand the role of window_stubs.c in the example ... is that just to avoid depending on some ocaml opengl library?

so if e.g. I used lablgl I would not need an extra .c file?

Exactly.

You're welcome. ;)