use strict;
use warnings;

use Inline C => <<'END_OF_C';
void foo() {
    char *s = (char *)malloc(100);
    sprintf(s, "%s", "hello there");
    printf("'%s'\n", s);
    free(s);    
}
END_OF_C

foo();

__END__

##</code><code>##


// gcc y.c
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>

void free(void *ptr);

void free(void *ptr){
        printf("my free called\n");
}
void foo() {
    char *s = (char *)malloc(100);
    sprintf(s, "%s", "hello there");
    printf("'%s'\n", s);
    free(s);
}
void main(void){ foo(); }

##</code><code>##

% a.out
'hello there'
my free called

##</code><code>##

// gcc x.c
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>

#define free myfree

void myfree(void *ptr);

void myfree(void *ptr){
        printf("my free called\n");
}
void foo() {
    char *s = (char *)malloc(100);
    sprintf(s, "%s", "hello there");
    printf("'%s'\n", s);
    free(s);
}
void main(void){ foo(); }