TCHAR转化为UTF8

char* tchar_to_utf8(const TCHAR* str) {
#ifdef _UNICODE
    int size = WideCharToMultiByte(CP_UTF8, 0, str, wcslen(str), NULL, 0, NULL, NULL);
    char* str8 = (char*) malloc(size+1);
    WideCharToMultiByte(CP_UTF8, 0, str, wcslen(str), str8, size, NULL, NULL);
    str8[size] = '\0';
    return str8;
#else
    return _strdup(str);
#endif
}