foo.cc: In function ‘int main()’:
foo.cc:13:10: warning: ‘a’ may be used uninitialized [-Wmaybe-uninitialized]
   13 |         c=a+b;
      |         ~^~~~
foo.cc:7:13: note: ‘a’ was declared here
    7 |         int a,b,c,n;
      |             ^