foo.cc:16:17: error: stray '\357' in program
  return step(n-1）+step（n-2)+step(n-3);
                 ^
foo.cc:16:18: error: stray '\274' in program
  return step(n-1）+step（n-2)+step(n-3);
                  ^
foo.cc:16:19: error: stray '\211' in program
  return step(n-1）+step（n-2)+step(n-3);
                   ^
foo.cc:16:25: error: stray '\357' in program
  return step(n-1）+step（n-2)+step(n-3);
                         ^
foo.cc:16:26: error: stray '\274' in program
  return step(n-1）+step（n-2)+step(n-3);
                          ^
foo.cc:16:27: error: stray '\210' in program
  return step(n-1）+step（n-2)+step(n-3);
                           ^
foo.cc: In function 'int step(int)':
foo.cc:16:20: warning: pointer to a function used in arithmetic [-Wpointer-arith]
  return step(n-1）+step（n-2)+step(n-3);
              ~~~~~~^~~~~
cc1plus: warning: pointer to a function used in arithmetic [-Wpointer-arith]
foo.cc:16:28: error: expected ')' before 'n'
  return step(n-1）+step（n-2)+step(n-3);
                            ^
foo.cc:16:20: error: invalid conversion from 'int (*)(int)' to 'int' [-fpermissive]
  return step(n-1）+step（n-2)+step(n-3);
              ~~~~~~^~~~~
foo.cc:10:5: note:   initializing argument 1 of 'int step(int)'
 int step(int n)
     ^~~~

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