foo.cc: In function 'int main()':
foo.cc:6:15: warning: left operand of comma operator has no effect [-Wunused-value]
    6 | for(int i=0; i<5, i++)
      |              ~^~
foo.cc:6:22: error: expected ';' before ')' token
    6 | for(int i=0; i<5, i++)
      |                      ^
      |                      ;

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