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_foo
c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!