foo.cc: In function 'char* ReverseString(char*)':
foo.cc:10:17: warning: NULL used in arithmetic [-Wpointer-arith]
     while(*q != NULL && *q != '\0')
                 ^~~~
foo.cc: At global scope:
foo.cc:26:22: error: '_TCHAR' has not been declared
 int _tmain(int argc, _TCHAR* argv[])
                      ^~~~~~

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