feat!: Remove MacOS-specific library flags (#111)

This now requires consumers to specify `-cc clang++` on their
executables when compiling on MacOS. This is the only way to get
Binaryen to link into OCaml code on Mac's Arm64 architecture.

README.md

@@ -42,6 +42,24 @@ This project aims to provide full feature parity with the [Binaryen C API](https
 
 None of these are particularly challenging to create bindings for—they just haven't been written yet. If you need anything that's missing, feel free to open a PR.
 
+## MacOS C++ Compiler
+
+When including this library in your `dune` MacOS executables, you'll need to specify `-cc clang++` in your `(ocamlopt_flags)` stanza. This is required because Binaryen will throw errors for itself to catch and using `clang++` is the only way to handle them correctly. You can find more info on this [ocaml issue](https://github.com/ocaml/ocaml/issues/10423).
+
+Your stanza could look something like this:
+
+```diff
+ (executable
+  (name example)
+  (public_name example)
+  (package example)
++ (ocamlopt_flags -cc clang++)
+  (modules example)
+  (libraries binaryen))
+```
+
+These flags likely won't work on other operating systems, so you'll probably need to use `dune-configurator` to vary the flags per platform. You can see an example of this in our [tests/](./tests/dune).
+
 ## Static Linking
 
 If you are planning to create portable binaries for Windows, it will try to find Cygwin/MinGW locations in your `PATH`. To avoid this, you probably want to add this to your `(executable)` stanzas:

src/dune

@@ -11,8 +11,6 @@
     binaryen_stubs_modules binaryen_stubs_settings ocaml_helpers)
   (flags -O2 -Wall -Wextra))
  (foreign_archives binaryen)
- (library_flags
-  (:include ./config/library_flags.sexp))
  (c_library_flags -lstdc++ -lpthread))
 
 (rule

test/config/dune

@@ -0,0 +1,8 @@
+(executable
+ (name ocamlopt_flags)
+ (libraries dune.configurator))
+
+(rule
+ (targets ocamlopt_flags.sexp)
+ (action
+  (run ./ocamlopt_flags.exe)))

test/config/ocamlopt_flags.ml

@@ -0,0 +1,16 @@
+module C = Configurator.V1
+
+let () =
+  C.main ~name:"ocamlopt_flags" (fun c ->
+      let default = [] in
+
+      let ocamlopt_flags =
+        match C.ocaml_config_var c "system" with
+        | Some "macosx" ->
+            (* These flags preserve the original C++ error behavior. Ref https://github.com/ocaml/ocaml/issues/10423 *)
+            [ "-cc"; "clang++" ]
+        | Some _ -> default
+        | None -> default
+      in
+
+      C.Flags.write_sexp "ocamlopt_flags.sexp" ocamlopt_flags)

test/dune

@@ -4,6 +4,8 @@
  (name test)
  (modules test)
  (libraries binaryen)
+ (ocamlopt_flags
+  (:include ./config/ocamlopt_flags.sexp))
  (action
   (run %{test})))
 
@@ -20,6 +22,8 @@
  (name test_native)
  (modules test_native)
  (libraries binaryen binaryen.native)
+ (ocamlopt_flags
+  (:include ./config/ocamlopt_flags.sexp))
  (action
   (run %{test})))