I just downloaded KDevelop because it scans header files to offer better suggestions in code completion.
I was looking at all the keywords it suggests when no header files are included at all:

Why is it recommending “incr”?
That’s not a C++ keyword.
What is it, and what is it used for?
I thought it might be short for increment..?
Probably it’s a bug. Looking at KDevelop source,
incrhas been add for code completion in filelanguages/cpp/codecompletion/context.cppon line 2326. It looks like a synonym to increment operation, however only valid synonyms are:and (&&), bitand (&), and_eq (&=), or (||), bitor (|), or_eq (|=), xor (^), xor_eq (^=), not (!), not_eq (!=), compl (~)