英文:
Call Go function with string parameter from C?
问题
我可以从C中调用一个没有参数的Go函数，如下所示。通过go build编译并打印输出：
Hello from Golang main function!CFunction says: Hello World from CFunction!Hello from GoFunction!
main.go
package main//extern int CFunction();import "C"import "fmt"func main() {fmt.Println("Hello from Golang main function!")//调用CFunction以便C调用GoFunctionC.CFunction()}//export GoFunctionfunc GoFunction() {fmt.Println("Hello from GoFunction!")}
file1.c
#include <stdio.h>#include "_cgo_export.h"int CFunction() {char message[] = "Hello World from CFunction!";printf("CFunction says: %s\n", message);GoFunction();return 0;}
现在，我想将一个字符串/字符数组从C传递给GoFunction。
根据cgo文档中的"C references to Go"部分，这是可能的，所以我给GoFunction添加了一个字符串参数，并将字符数组message传递给GoFunction：
main.go
package main//extern int CFunction();import "C"import "fmt"func main() {fmt.Println("Hello from Golang main function!")//调用CFunction以便C调用GoFunctionC.CFunction()}//export GoFunctionfunc GoFunction(str string) {fmt.Println("Hello from GoFunction!")}
file1.c
#include <stdio.h>#include "_cgo_export.h"int CFunction() {char message[] = "Hello World from CFunction!";printf("CFunction says: %s\n", message);GoFunction(message);return 0;}
在执行go build时，我收到以下错误：
./file1.c:7:14: error: passing 'char [28]' to parameter of incompatible type 'GoString'./main.go:50:33: note: passing argument to parameter 'p0' here
根据上述"C? Go? Cgo!"博客文章中的"strings and things"部分：
> 在Go和C字符串之间的转换是通过C.CString、C.GoString和C.GoStringN函数完成的。
但是这些函数是用于在Go中使用的，如果我想将字符串数据传递到Go中，它们并不是很有用。
英文:
I can call a Go function without parameters from C, per below. This compiles via go build and prints
Hello from Golang main function!CFunction says: Hello World from CFunction!Hello from GoFunction!
main.go
package main//extern int CFunction();import "C"import "fmt"func main() {fmt.Println("Hello from Golang main function!")//Calling a CFunction in order to have C call the GoFunctionC.CFunction();}//export GoFunctionfunc GoFunction() {fmt.Println("Hello from GoFunction!")}
file1.c
#include <stdio.h>#include "_cgo_export.h"int CFunction() {char message[] = "Hello World from CFunction!";printf("CFunction says: %s\n", message);GoFunction();return 0;}
Now, I want to pass a string/char array from C to GoFunction.
According to "C references to Go" in the cgo documentation this is possible, so I add a string parameter to GoFunction and pass the char array message to GoFunction:
main.go
package main//extern int CFunction();import "C"import "fmt"func main() {fmt.Println("Hello from Golang main function!")//Calling a CFunction in order to have C call the GoFunctionC.CFunction();}//export GoFunctionfunc GoFunction(str string) {fmt.Println("Hello from GoFunction!")}
file1.c
#include <stdio.h>#include "_cgo_export.h"int CFunction() {char message[] = "Hello World from CFunction!";printf("CFunction says: %s\n", message);GoFunction(message);return 0;}
Upon go build I receive this error:
./file1.c:7:14: error: passing 'char [28]' to parameter of incompatible type 'GoString'./main.go:50:33: note: passing argument to parameter 'p0' here
According to the "strings and things" section of the above "C? Go? Cgo!" blog post:
> Conversion between Go and C strings is done with the C.CString, C.GoString, and C.GoStringN functions.
But these are for use in Go, and not helpful if I want to pass string data into Go.
答案1
得分: 6
在C中，字符串是*C.char类型，而不是Go中的string类型。请确保你的导出函数接受正确的C类型，并在Go中进行必要的转换：
//export GoFunctionfunc GoFunction(str *C.char) {fmt.Println("Hello from GoFunction!")fmt.Println(C.GoString(str))}
英文:
A string in C is a *C.char, not a Go string.
Have your exported function accept the correct C type, and convert it as necessary in Go:
//export GoFunctionfunc GoFunction(str *C.char) {fmt.Println("Hello from GoFunction!")fmt.Println(C.GoString(str))}
答案2
得分: 4
如果你想将一个只接受Go字符串的函数传递给一个C字符串，你可以在C端使用GoString类型：
char message[] = "Hello World from CFunction!";printf("CFunction says: %s\n", message);GoString go_str = {p: message, n: sizeof(message)}; // 注意：sizeof(message)只适用于数组，不适用于指针。GoFunction(go_str);return 0;
英文:
If you want to pass a C string to a function that accepts only Go strings, you can use GoString type on the C side:
char message[] = "Hello World from CFunction!";printf("CFunction says: %s\n", message);GoString go_str = {p: message, n: sizeof(message)}; // N.B. sizeof(message) will// only work for arrays, not// pointers.GoFunction(go_str);return 0;
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