foo.cc: In function 'int main()':
foo.cc:8:9: warning: 'a' is used uninitialized in this function [-Wuninitialized]
    8 |  cout<<a+b+c+d<<endl;
      |        ~^~
foo.cc:8:9: warning: 'b' is used uninitialized in this function [-Wuninitialized]
foo.cc:8:11: warning: 'c' is used uninitialized in this function [-Wuninitialized]
    8 |  cout<<a+b+c+d<<endl;
      |        ~~~^~
foo.cc:8:14: warning: 'd' is used uninitialized in this function [-Wuninitialized]
    8 |  cout<<a+b+c+d<<endl;
      |              ^

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