I am trying to use CGO to call an optimized C++ CPU-bound implementation of a complex algorithms from golang. Basically, it will pass a string into c++ function and get a string back. A simplified version of the code can be seen in the below:
//algo.go
package main
//#cgo LDFLAGS:
//#include <stdio.h>
//#include <stdlib.h>
//#include <string.h>
//char* echo(char* s);
import "C"
import "unsafe"
func main() {
cs := C.CString("Hello from stdio
")
defer C.free(unsafe.Pointer(cs))
var echoOut *C.char = C.echo(cs)
//defer C.free(unsafe.Pointer(echoOut)); -> using this will crash the code
fmt.Println(C.GoString(echoOut));
}
//algo.cpp
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <math.h>
using namespace std;
extern "C" {
char* echo(char* o) {
int len = sizeof(o) / sizeof(char);
char* out = (char*)malloc(len * sizeof(char));
strcpy(out, o);
return out;
}
}
In this link, ppl mentions that C++ code should call "free" by itself to free the allocated memory: http://grokbase.com/t/gg/golang-nuts/149hxezftf/go-nuts-cgo-is-it-safe-to-malloc-and-free-in-seperate-c-functions. But then it's very tricky because my c++ function return an allocated pointer so that golang can get the result. I cannot call free in the c++ code? What should be the correct way to handle this? I have a webserver will call the c++ code per each request and want to make sure it doesn't introduce any memory leak.
Thanks.