Interesting. Our compiler catches it, though:

  $ cparser -O3 -Wall -Wextra -pedantic test2.c -o uninit
  warning: ignoring gcc option '-pedantic'
  test2.c:3:6: warning: no previous declaration for 'void foo(int)' [-Wmissing-declarations]
  1 warning(s)
  test2.c:4:6: warning: 'variable lol' might be used uninitialized [-Wuninitialized]

Looking at the GCC bugtracker, there seem to be various warnings missing. http://gcc.gnu.org/bugzilla/buglist.cgi?quicksearch=uninitia...