Re: master 544db1e: Faster grep pattern for identifiers

[Dmitry Gutov]

On 15.09.2021 18:56, Eli Zaretskii wrote:
> > branch: master
> > commit 544db1ee8679eec9edd5cee81a340ee1c4d70158
> > Author: Mattias Engdegård<mattiase@acm.org>
> >
> >      Faster grep pattern for identifiers
> >      
> >      * lisp/cedet/semantic/symref/grep.el (semantic-symref-perform-search):
> >      Use the `-w` flag instead of wrapping the pattern in regexps that make
> >      matching much slower.  This speeds up `xref-find-references` by about
> >      3× on macOS.
> Doesn't this change the semantics of the "word"?  The Grep notion of
> the word is not necessarily identical to that of Emacs, since the
> latter depends on the major mode.  The comment in the deleted code
> says that much, AFAICT.  Or what am I missing?

Luckily, -w actually corresponds to the regexp which the previous 
version of the code was using. Rather than to \<...\> which one might 
surmise from reading the docs for some versions of Grep (or Ripgrep).

And the comment was about \< and \>.

The latest Grep manual describes it correctly:

       -w, --word-regexp
              Select  only  those  lines  containing  matches  that 
form whole words.  The test is that the matching substring must either 
be at the beginning of the line, or preceded by a non-word
              constituent character.  Similarly, it must be either at 
the end of the line or followed by a non-word constituent character. 
Word-constituent characters are letters, digits, and  the
              underscore.