Question

If I have this function foo() and I’m calling it from another function foo2(); must I free the memory in the calling function like this?

char *foo(char *str1){
    char *str2;
    str2 = malloc((sizeof(char) * strlen(str1)) + 1);
    memcpy(str2, str1, strlen(str1) + 1)
    return str2;
}

void foo2(void){
    char *str1 = "Hello world!"
    char *str2;
    str2 = foo(str1);
    ...some stuff
    free(str2); //Should I do this here?
}

Answer 1

Yes, it is right. foo() allocates some memory and it must be freed by the caller. It’s not a very good design but it works. It could be better if foo() accepts two parameters: output buffer and its size.

void foo(char* input, char* output, int* bufferSize);

If output is NULL the required size is written in bufferSize by foo().