/in/foo.cc: In function 'int gcd(int)':
/in/foo.cc:23:16: warning: 'n' is used uninitialized in this function [-Wuninitialized]
  for(int i=1; i<n; i++)
               ~^~
/in/foo.cc: In function 'int main()':
/in/foo.cc:25:4: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   r=x%x1;
   ~^~~~~
/in/foo.cc:22:8: note: 'x' was declared here
  int n,x,r;
        ^
/in/foo.cc: In function 'int gcd(int)':
/in/foo.cc:25:4: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   r=x%x1;
   ~^~~~~