Identifiers starting with underscores are reserved by C++ standard

[yeputons]

See this for clarification. Strictly speaking, declaring a reserved identifier is undefined behavior, which means that as long as testlib does that, all checkers and validators have undefined behavior as well. I have not seen any problems with this in the wild so far (except for the famous), but the problem is here.

Some examples from testlib's code: _ok, _wa, __testlib_max.
I believe that the correct way of resolving this is to add a special namespace testlib and add a bunch of #defines to preserve backward compatibility.