/in/foo.cc: In function 'int random()':
/in/foo.cc:6:5: error: ambiguating new declaration of 'int random()'
 int random()
     ^~~~~~
In file included from /usr/include/c++/6/cstdlib:75:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:47,
                 from /in/foo.cc:1:
/usr/include/stdlib.h:282:17: note: old declaration 'long int random()'
 extern long int random (void) __THROW;
                 ^~~~~~