我使用
C->Haskell Compiler, version 0.25.2 Snowboundest, 31 Oct 2014 build platform is "x86_64-darwin" <1, True, True, 1>;生成命令:

c2hs Structs.chs
ghci Structs.hs

但链接器抱怨
During interactive linking, GHCi couldn't find the following symbol: get_foo

问:这是为什么,我该怎么解决?THX提前
A:TL;博士:我没有把.C编译成.O目标代码,对吧!
代码如下:
结构.chs
module Main where

import Foreign
import Foreign.C

#include "Structs.h"

{#pointer *foo as Foo#}

{#fun get_foo {`Int'} -> `Foo' return* #}

main :: IO ()
main = do
  foo <- get_foo 3
  a1 <- {#get struct foo->a#} foo
  print a1

结构H
struct foo {
  int a;
};

struct foo *get_foo(int n);

结构C
#include "Structs.h"

struct foo f;

struct foo *get_foo(int n)
{
  f.a = n;
  return &f;
}

结构.hs
-- -- C2HS generated Hs file, edited for clarity
module Main where

import Foreign
import Foreign.C

type Foo = Ptr ()

get_foo :: Int -> IO Foo
get_foo p =
  get_foo'_ (fromIntegral p)

main :: IO ()
main = do
  foo <- get_foo 3
  a1 <- (\ptr -> peekByteOff ptr 0 :: IO CInt) foo
  print a1

foreign import ccall safe "Structs.chs.h get_foo"
  get_foo'_ :: CInt -> IO Foo

编辑:ghc --make Structs.hs给出相同的链接器错误:
$ ghc --make Structs.hs
Linking Structs1a ...
Undefined symbols for architecture x86_64:
"_get_foo", referenced from:
    _c2MX_info in Structs.o
    _c2Or_info in Structs.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

最佳答案

get_fooc函数在Structs.c中定义,因此您需要将其提供给ghc。这应该管用:

gcc -o Structs_c.o -c Structs.c
ghc --make Structs.hs Structs_c.o

对于ghci,我想你可以说ghci Structs.hs Structs_c.o。但你肯定需要C对象文件!

10-06 10:32
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