英文:
How to convert C uint64_t to Cgo consistently across OS?
问题
我正在使用一些C库来处理Go语言，使用cgo来处理转换。
我有一个C头文件，看起来像这样：
#include <stdlib.h>
typedef struct {
uint64_t k;
} params;
这个结构体在Go语言中被使用，代码如下：
package test
/*
#cgo CFLAGS: -g -Wall
#cgo LDFLAGS: -L. -lmylib -lm -ldl
#include "mylib.h"
*/
import "C"
func NewParams(k uint64) Params {
return Params{
k: C.ulonglong(k),
}
}
这段代码在使用Apple clang版本12.0.0的OS X上编译正常，但在使用clang版本7.1.0的Linux上失败，出现以下错误：
cannot use _Ctype_ulonglong(k) (type _Ctype_ulonglong) as type _Ctype_ulong in field value
如果我将调用C.ulonglong改为C.ulong，它在Linux上可以正常工作，但在OS X上失败。
如何确保相同的代码在两个平台上都能正常工作？
英文:
I am using some C library form Go, using cgo to handle the conversion.
I have a C header file that looks like:
#include <stdlib.h>
typedef struct {
k uint64_t;
} params;
This structure is used from Go with code like:
package test
/*
#cgo CFLAGS: -g -Wall
#cgo LDFLAGS: -L. -lmylib -lm -ldl
#include "mylib.h"
*/
import "C"
func NewParams(k uint64) Paramets {
return Params{
k: C.ulonglong(k),
}
}
The code compiles fine on OS X with Apple clang version 12.0.0, but fails on Linux with clang version 7.1.0, yielding the following error:
cannot use _Ctype_ulonglong(k) (type _Ctype_ulonglong) as type _Ctype_ulong in field value
If I change the call to C.ulonglong to C.ulong, it works fine on linux but then fails on OS X.
How can I ensure the same code works on both platform?
答案1
得分: 2
使用go build -work，我确认问题源于映射差异：
- 在Linux端，C的
unit64_t被映射为C.ulong - 在Mac端，它被映射为
C.ulonglong
请注意，C.ulong和C.ulonglong都被映射为Go的uint64，但直接使用Go类型并删除C.xxx(k)转换会失败。
解决方案是使用C.uint64_t(k)，这样可以明确指定我们正在讨论的类型的大小。这是完全可以的，因为C类型本身就是uin64_t。
英文:
Using go build -work I was able to confirm the issue stems from differences in mapping:
- On the linux side, a C
unit64_tgets mapped to aC.ulong - On the Mac side, it gets mapped to
C.ulonglong
Note that both C.ulong and C.ulonglong gets mapped to a go uint64 but using the Go type directly and removing the C.xxx(k) conversion fails.
Solution is to use C.uint64_t(k) which makes it explicit the size of the type we are talking about. This is just fine because the C type is uin64_t anyways.
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