Call function by string with params

//the original code is not by me (but it is without params)

#include <cstdio>
#include <cstdlib>
#include <iostream>

/* These are your handler functions */
void user_fn(char params[]) { printf("USER fn\n%s\n",params); }
void pass_fn(char params[]) { printf("PASS fn\n%s\n",params); }

/* Stores a C string together with a function pointer */
typedef struct fn_table_entry {
    char *name;
    void (*fn)(char params[]);
} fn_table_entry_t;

/* These are the functions to call for each command */
fn_table_entry_t fn_table[] = {{"USER", user_fn}, {"PASS", pass_fn}};

/* fn_lookup is a function that returns the pointer to the function for the given name.
   Returns NULL if the function is not found or if the name is NULL. */
void (*fn_lookup(const char *fn_name))(char params[]) {
    int i;

    if (!fn_name) {
        return NULL;
    }
    for (i = 0; i < sizeof(fn_table)/sizeof(fn_table[0]); ++i) {
        if (!strcmp(fn_name, fn_table[i].name)) {
            return fn_table[i].fn;
        }
    }
    return NULL;
}

int main() {
    fn_lookup("USER")("char");
    fn_lookup("PASS")("int");

    system("pause");
    return 0;
}

//example by user470379 without parameters