Description:
File i.c:
#include <stdlib.h>
int main(){return(random());}
// gcc i.c -std=c99

------------------
compilation yields:
i.c:2:1: warning: implicit declaration of function ‘random’ [-Wimplicit-function-declaration]

Additional info:
Fails on the two Linux systems where I tested it.

gcc version 4.6.4 (GCC)
gcc version 4.4.7 20120313 (Red Hat 4.4.7-11) (GCC)

-bash-4.1$ openssl md5 /usr/include/stdlib.h
MD5(/usr/include/stdlib.h)= bb6d8d92d80fc6b84f9a46747bdb2169

For what it is worth:
gcc requires -std=c99 for construct beginning "for(int j =0; ...)"
clang does not.
Test fails to fail without -std=c99

Steps to reproduce:

Compile file i.c thus:
gcc i.c -std=c99