Latest one that wasted my time was to find that 'major' and 'minor' are secretly reserved keywords in C++, though this is undocumented.

Did not know that.

Is that a language hidden spec, or a vendor hidden spec?

It's some vendor thing, its a real error IMO since the integrated IDE doesn't know about this as far as syntax coloring goes, but I finally changed the names of those member functions to be Minor and Major and the problem vanished, meaning it's doing some shit with them, probably they have something that should have been called __MAJOR and __MINOR. The error message didn't even point at the right line number it threw the compiler off so far.

"secretly reserved keywords in C++" was meant to be said sarcastically, sorry that I didn't make it more clear there.