package main

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

char* str_to_lower(char* str) {
    char* p = str;
    if(str == NULL || str[0] == '\0') {
        return str;
    }
    for(; *p != '\0'; p++) {
        *p = tolower(*p);
    }
    return str;
}
*/
import "C"
import "unsafe"

func str_to_lower(s string) string {
    cs1 := C.CString(s)
    defer C.free(unsafe.Pointer(cs1))

    cs2 := C.str_to_lower(cs1)
    defer C.free(unsafe.Pointer(cs2))

    return C.GoString(cs2)
}

func main() {
    println(str_to_lower(""))
}