programmatically mocking a function
#include <stdio.h>

void someFunc( void )
{
    printf("%s():%dn",__func__,__LINE__);
}

void someBlah( void )
{
    printf("%s():%dn",__func__,__LINE__);
}

int main(void)
{
    someFunc();
}

#define BLAH 0
#define FOO 1
void (*table_function[])(void) = {someBlah, someFoo};

table_function[BLAH]();

table_function[BLAH] = otherBlah;

#include <stdio.h>
#define DEBUG

void someFunc( void )
{
#ifndef DEBUG
    printf("%s():%dn",__func__,__LINE__);
#else
    printf("%s():%dn",__func__,__LINE__);
#endif
}

int main(void)
{
    someFunc();
}