Problems with syntax-ppss

[Alan Mackenzie <acm@muc.de>]

Hi, Emacs!

I've just encountered a rather knotty problem in CC Mode for which
syntax-ppss ought to be a solution; I need to find out, RAPIDLY, whether
a particular buffer position is inside a string or comment.
Unfortunately (for me), ......

syntax-ppss does it's parsing from (point-min), not from BOB.

So if the buffer is currently narrowed, this function will return an
meaningless value for the envisaged use.

But if I widen the buffer first, what happens to syntax-ppss's cache?
Is this just discarded, or are perhaps two caches maintained (one from
BOB, the other from the current (or most recent) (point-min)?

Advice, please!

Forgive me at this point for not reading the fine source code - it's
over 150 lines and looks rather forbidding.

It would be nice if the the Elisp manual could be more explicit on such
points.  (Hey, tell me how it is, and I'll expand the manual!)

I think the doc-string for the function is inadequate - it fails to
state that parsing starts at (point-min) rather than BOB.

Thanks in advance!

-- 
Alan Mackenzie (Nuremberg, Germany).