foo.cc:5:12: warning: missing terminating " character
     cout <<"hello,world! << endl;
            ^
foo.cc:5:12: error: missing terminating " character
     cout <<"hello,world! << endl;
            ^~~~~~~~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:6:5: error: expected primary-expression before 'return'
     return 0;
     ^~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。