ocamlfind抱怨没有为通过opam安装的模块提供实现

Question

我正在弄乱OCaml FFI试图弄清楚如何推断C enum的宽度(我认为是C的实现定义)并且我试图插入一个错误宽度的类型来看看有什么打击在运行时.这就是动力,但我遇到的实际问题更为平凡.

我有一个简单的OCaml文件,它使用C FFI调用一个简单的函数example.c,将枚举转换为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并安装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

我用来编写一个简单.ml脚本的两个常用咒语都让我失望,而且我没有想法.ocamlfind和corebuild(我认为它是一个封装的顶部ocamlbuild)

ocamlfind似乎无法找到ctypes和foreign.但是,它并没有抱怨无法找到软件包所以我猜测ctypes并且ctypes.foreign是奇怪的findlib命名空间中这些软件包的正确名称.

% 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？我把它们加载到顶层是没有问题的.

?( 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;;

Answer 1

在我看来,你忘记添加-linkpkgocamlfind选项来指示编译器实际链接包中的库以构建可执行文件.