释放Golang中的C变量？

Question

如果我在Go中使用C变量，我很困惑哪些变量需要释放。

例如，如果我这样做：

    s := C.CString(`something`)

是在我调用C.free(unsafe.Pointer(s))之前分配了该内存，还是在函数结束时可以由Go进行垃圾回收？

或者仅是从导入的C代码创建的变量需要释放，而这些从Go代码创建的C变量将被垃圾回收？

Answer 1

documentation does mention：

// Go string to C string
// The C string is allocated in the C heap using malloc.
// It is the caller's responsibility to arrange for it to be
// freed, such as by calling C.free (be sure to include stdlib.h
// if C.free is needed).
func C.CString(string) *C.char

wiki shows an example：

package cgoexample

/*
#include <stdio.h>
#include <stdlib.h>

void myprint(char* s) {
        printf("%s", s);
}
*/
import "C"

import "unsafe"

func Example() {
        cs := C.CString("Hello from stdio\n")
        C.myprint(cs)
        C.free(unsafe.Pointer(cs))
}

---

文章“ C? Go? Cgo!”表明您不需要释放C数字类型：

func Random() int {
    var r C.long = C.random()
    return int(r)
}

但是您会输入字符串：

import "C"
import "unsafe"

func Print(s string) {
    cs := C.CString(s)
    C.fputs(cs, (*C.FILE)(C.stdout))
    C.free(unsafe.Pointer(cs))
}

Answer 2

从C释放内存是否有效？

package cgoexample

/*
#include <stdio.h>
#include <stdlib.h>

void myprint(char* s) {
    printf("%s", s);
    if (s != NULL) {
        free(s);
    }
}
*/
import "C"

import "unsafe"

func Example() {
        cs := C.CString("Hello from stdio\n")
        C.myprint(cs)
}