英文:
unexpected type: ... with cgo in Go
问题
我是你的中文翻译助手，以下是你要翻译的内容：
我是Go语言的新手，正在尝试学习如何从Go中调用C语言。我编写了这个程序来打开一个命名信号量，获取其值并将其打印到屏幕上。
当我运行go build semvalue.go时，我收到以下错误信息：
./semvalue.go:16:14: unexpected type: ...
这是什么意思？我做错了什么？
package main
import "fmt"
// #cgo LDFLAGS: -pthread
// #include <stdlib.h>
// #include <fcntl.h>
// #include <sys/stat.h>
// #include <semaphore.h>
import "C"
func main() {
name := C.CString("/fram")
defer C.free(unsafe.Pointer(name))
fram_sem := C.sem_open(name, C.O_CREAT, C.mode_t(0644), C.uint(1))
var val int
ret := C.sem_getvalue(fram_sem, &val)
fmt.Println(val)
C.sem_close(fram_sem)
}
谢谢。
英文:
I'm new to Go and trying to learn how to call C from Go. I wrote this program to open a named semaphore, get the value and print it to the screen.
When I run it go build semvalue.go I get the error:
./semvalue.go:16:14: unexpected type: ...
What does this mean? What am I doing wrong?
package main
import "fmt"
// #cgo LDFLAGS: -pthread
// #include <stdlib.h>
// #include <fcntl.h>
// #include <sys/stat.h>
// #include <semaphore.h>
import "C"
func main() {
name := C.CString("/fram")
defer C.free(name)
fram_sem := C.sem_open(name, C.O_CREAT, C.mode_t(0644), C.uint(1))
var val int
ret := C.sem_getvalue(fram_sem, val)
fmt.Println(val)
C.sem_close(fram_sem)
}
Thank you.
答案1
得分: 14
这条消息有些混乱，直到你意识到...是C函数的可变参数部分。你不能直接从Go中使用C的可变参数函数，所以你需要编写一个小的C包装器来调用sem_open。
还有几点需要注意：
C.free应该使用C.free(unsafe.Pointer(name))进行调用。val需要是一个*C.int类型。sem_getvalue使用了errno，所以你应该使用ret, err := C.sem_getvalue...进行调用。
英文:
The message is confusing, until you realize that the ... is the variadic portion of a C function. You can't use C variadic functions directly from Go, so you'll have to write a small wrapper in C to call sem_open.
A couple more notes:
C.freeshould be called withC.free(unsafe.Pointer(name))valneeds to be a*C.intsem_getvalueuseserrno, so you should call it withret, err := C.sem_getvalue...
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