On 24 Dec 2016 5:44 pm, "Alan Mackenzie" <acm@muc.de> wrote:

This slowdown in Paul's config.h no longer happens, because of a
workaround put into syntax.c, I can't remember exactly what or when.
However, just last week, there was yet one more bug reported to CC Mode
about indentation, whose cause was a paren in C0 inside a comment. I
would like these bug reports to cease. As you said back in March, Emacs
should be able to handle these, as they are valid C.

I'm sorry for raising a question which may have an obvious answer, but as I I have been following this thread I have become somewhat concerned with confused as to the underlying cause of this issue.

Could you or someone else explain why an open paren in column 0 can affect the parsing of syntax in cc-mode at all? After all, such parens have no special syntactic nor semantic meaning in C nor C++.

Regards,

Elias