Re: imenu fails in mode without comment-start-skip defined

[Richard Stallman]

    > Well, it's easy to measure.  Using syntax-ppss instead of the current
    > code makes imenu--make-index-alist 4 times faster when run on
    > simple.el (rather surprisingly).  It's 50% slower than without any
    > check on the context.

    I.e. the current code with comment-beginning is 6 times slower than before?
    Sounds like a very good reason to remove this comment-beginning stuff,

Maybe so.

As regards using syntax-ppss, I'm worried that in certain modes it
would have to scan all the way to the beginning of the buffer over and
over.  In those modes, it could be hundreds of times slower on a large
file.

Maybe this is not really a possibility.  Maybe it depends on whether
the loop scans forwards or backwards.  It would depend on what kind of
caching features there are inside syntax-ppss, which is a question I
don't recall the answer to.