Dune Ctypes seems to fail silently

Learning
1

Hello,
I followed this sample and everything compiles but dune exec ./bin/main.exe seems to fail silently. I did see the first print statement earlier.

open Ctypes
let () =
  let size' = Unsigned.Size_t.of_int 4 in
  let fp  = CArray.of_list float [1.;1.;1.;1.]  in
  let conf = 0 in
  let _ = C.Functions.init_distance_functions conf in
  Printf.printf "DEBUG";
  Printf.printf " %f" ( C.Functions.simd_euclidean (CArray.start fp) (CArray.start fp) size' );

This dune file looks complicated but I don’t see any error anywhere.

(executable
 (public_name vectordb)
 (name main)
 ; ctypes backward compatibility shims warn sometimes; suppress them
 (flags (:standard -w -9-27))
 (libraries ctypes ctypes-foreign )
 (ctypes
  (external_library_name libvector)
  (build_flags_resolver
   ; Change the -I to point to the directory containing your header files,
   ; which you need for the ctypes struct definitions
   (vendored
    (c_flags :standard -Wall -Werror -I../libvector)
    (c_library_flags :standard -Wall -Werror )))
  (headers
   (include "simd_distance.h" "simd_ops.h"))
  (type_description
   (instance Types)
   (functor Type_description))
  (function_description
   ; Set this to sequential if the library is not thread-safe
   (concurrency unlocked)
   (instance Functions)
   (functor Function_description))
  (generated_types Types_generated)
  (generated_entry_point C))
 (foreign_archives vectordb))


(data_only_dirs libvector)

(rule
 (deps
  (source_tree ../libvector))
 (targets libvectordb.a dllvectordb.so)
 (action
  (no-infer
   (progn
    (chdir
     ../libvector
     (run make))
    (copy ../libvector/libvectordb.a libvectordb.a)
    (copy ../libvector/dllvectordb.so dllvectordb.so)
    ))))

The Makefile is

CC = /opt/homebrew/opt/llvm/bin/clang
# CFLAGS = -O3 -march=armv9-a+sme -mcpu=apple-m4 -framework Accelerate

CFLAGS = -O3 -arch arm64 -mcpu=apple-m4 -framework Accelerate

all: libvectordb.a dllvectordb.so

simdd.o: simd_distance.c simd_distance.h
	$(CC) $(CFLAGS) -c -o simdd.o simd_distance.c

simdo.o: simd_ops.c simd_ops.h
	$(CC) $(CFLAGS) -c -o simdo.o simd_ops.c

libvectordb.a: simdd.o simdo.o
	ar rcs $@ simdd.o simdo.o
	@echo "Signing library..."
	codesign -s - $@

dllvectordb.so: libvectordb.a
	$(CC) -shared -o $@ $^

clean:
	rm -f *.o *.a

I am signing my binary now because later I want to use M4’s Scalable Vector Extensions..

The C code is

float euclidean_fallback(const float* a, const float* b, size_t n) {
    float sum = 0.0f;
    for (size_t i = 0; i < n; i++) {
        float diff = a[i] - b[i];
        sum += diff * diff;
    }
    return sqrtf(sum);
}

function_description.ml

(* function_description.ml *)
open Ctypes

module Types = Types_generated

module Functions (F : Ctypes.FOREIGN) = struct
  open F

  let simd_euclidean = foreign "simd_euclidean" (ptr float @-> ptr float @-> Ctypes.size_t @-> returning float)
  let init_distance_functions = foreign "init_distance_functions" (int @-> returning void)

end

I don’t see the printed values now.

Thanks.

2

I had to change it back to

CFLAGS = -O3 -march=armv9-a+sme+sme2 -mcpu=apple-m4 -framework Accelerate

to get the original error.

zsh: illegal hardware instruction dune exec ./bin/main.exe

Update : I commented /* #if defined(__AVX__) */ in other places but dune doesn’t print anything.

But lldb does

 lldb ../_build/default/vectordb/bin/main.exe 
<    lldb ../_build/default/vectordb/bin/main.exe 
(lldb) target create "../_build/default/vectordb/bin/main.exe"
Current executable set to '/Users/anu/Documents/rays/_build/default/vectordb/bin/main.exe' (arm64).
(lldb) run
run
Process 5040 launched: '/Users/anu/Documents/rays/_build/default/vectordb/bin/main.exe' (arm64)
0 Euclidean 0.000000Process 5040 exited with status = 0 (0x00000000) 
(lldb)

Not sure how I can debug more complex code like this. Am I missing something ? I will add expect tests too.

Thanks.