ocamlfind抱怨没有为通过opam安装的模块提供的实现
问题描述:
我正在搞砸OCaml FFI以试图弄清楚它是如何推断C枚举的宽度(我认为是C实现定义的),而且是上午试图插入一个错误宽度的类型来查看在运行时发生了什么。这是动机,但我遇到的实际问题更为普遍。ocamlfind抱怨没有为通过opam安装的模块提供的实现
我有一个简单的OCaml文件,它使用C FFI调用example.c
中的一个微不足道的函数,它将enum转换为int。
open Printf;;
let (@->) = Ctypes.(@->);;
let returning = Ctypes.returning;;
let foreign = Foreign.foreign;;
(* deliberately use the wrong scalar type for argument *)
let wrong_int64_of_color =
foreign "int_of_color" (Ctypes.int64_t @-> returning Ctypes.int64_t);;
let main() =
printf "%Ld\n" (wrong_int64_of_color (Int64.of_int 100));;
let() = main();;
我配置OPAM和安装Ctypes
和Ctypes.Foreign
% opam config env | sed -e 's/=.*/=/'
CAML_LD_LIBRARY_PATH=
OPAMUTF8MSGS=
MANPATH=
PERL5LIB=
OCAML_TOPLEVEL_PATH=
PATH=
% opam list | grep ctypes
ctypes 0.6.2 Combinators for binding to C libraries withou
ctypes-foreign 0.4.0 Virtual package for enabling the ctypes.forei
两个常用的咒语我用编译一个简单的脚本.ml
双双失败了我和我的想法。 ocamlfind
和corebuild
(我认为这是对的ocamlbuild
一种包装)
ocamlfind似乎无法找到和foreign
。然而,它并没有抱怨说无法找到包,所以我猜和ctypes.foreign
是这些包在奇怪的findlib
命名空间中的正确名称。
% ocamlfind ocamlopt -package findlib,ctypes,ctypes.foreign -thread call_example.ml
File "_none_", line 1:
Warning 58: no cmx file was found in path for module Foreign, and its interface was not compiled with -opaque
File "call_example.ml", line 1:
Error: No implementations provided for the following modules:
Ctypes referenced from call_example.cmx
Foreign referenced from call_example.cmx
为什么ocamlfind
找不到这些模块?我没有问题加载到顶层。
─(22:30:42)─< command 0
utop # #require "ctypes";;
─(22:30:42)─< command 1
utop # open Ctypes;;
─(22:30:55)─< command 2
utop # #require "ctypes.foreign";;
─(22:31:00)─< command 3
utop # open Ctypes;;
答
在我看来,你忘了加上-linkpkg
ocamlfind选项指示编译器实际上从包链接库来构建可执行文件。