If that is a member variable, and if the next character is neither an underscore nor an uppercase letter, that is actually okay, because the rule about such identifiers does not reserve them to the implementation when they are member variables (or local to a function, or within a namespace other than the global and ::std namespaces). But it can be a bother to keep the nitty gritty of these rules in mind all the time, hence my suggestion of appending a single underscore if you want to use an underscore for this purpose.Originally Posted by g4j31a5