Re: [Emacs-diffs] comment-cache 223d16f 2/3: Apply `comment-depth' text properties when calling `back_comment'.

[Dmitry Gutov]

On 03/12/2016 11:29 PM, Clément Pit--Claudel wrote:

> Does this break on
>
>   /<point>* test */
>
> in C mode? (<point> indicate the position of the point)

If by break you mean does nothing, then yes. In what practical 
situations is this a problem?

There might be ways to alleviate it (make syntax-ppss scan forward a 
little, e.g. till the end of the line), but a naive solution might mess 
up how syntax-propertize works:

a) It wraps the calls to syntax-propertize-function in 
inhibit-modification-hooks.

b) That function is allowed to call syntax-ppss as well, and then modify 
the syntax-table property of any position after the call. If syntax-ppss 
is allowed to rely on the syntax class of '*', it might return (and 
cache) a value that will turn out to be false in the future.

*If* the issue is an actual problem, the best way to handle it might be 
in the caller of syntax-ppss. If the caller is not a part of 
syntax-propertize-function, or at least it doesn't inhibit modification 
hooks, it can try evaluating (nth 8 (syntax-ppss pos)) in several 
positions - from (point) to (+ (point) n -1), where n is the maximum 
length of a comment starter in the current language. When one of the 
calls returns a non-nil position (but one that's before point) => jump 
there.