foo.cc: In function 'int main()':
foo.cc:25:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^
foo.cc:19:14: note: 'c' was declared here
  int a=1,b=1,c;
              ^
foo.cc: In function 'long long int fib(int)':
foo.cc:25:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^

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