foo.cc: In function 'int main()':
foo.cc:60:3: warning: 'num1' may be used uninitialized in this function [-Wmaybe-uninitialized]
   ++num1;
   ^~~~~~
foo.cc:66:3: warning: 'num2' may be used uninitialized in this function [-Wmaybe-uninitialized]
   ++num2;
   ^~~~~~
foo.cc:80:3: warning: 'num3' may be used uninitialized in this function [-Wmaybe-uninitialized]
   ++num3;
   ^~~~~~
foo.cc:86:3: warning: 'num4' may be used uninitialized in this function [-Wmaybe-uninitialized]
   ++num4;
   ^~~~~~