On 24 Dec 2016 5:44 pm, "Alan Mackenzie" 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