From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Vaidheeswaran C <vaidheeswaran.chinnaraju@gmail.com>
Cc: 20806@debbugs.gnu.org
Subject: bug#20806: 25.0.50; `string-match' is confused???
Date: Sun, 14 Jun 2015 09:40:33 -0400 [thread overview]
Message-ID: <jwvpp4yl8eo.fsf-monnier+emacsbugs@gnu.org> (raw)
In-Reply-To: <557BF8E9.9040007@gmail.com> (Vaidheeswaran C.'s message of "Sat, 13 Jun 2015 15:03:29 +0530")
tags 20806 notabug
thanks
> Is an empty string a prefix of all strings or not?
Yes, but that's unrelated to the uncaught signal you show, nor to the
two string-match calls you show.
> Welcome to the Emacs shell
> /tmp $ (string-match "\\(.*\\)" "")
> 0
Yup, we can find a trivial match for "\\(.*\\)" in the empty string.
> /tmp $ (string-match "foo" "")
And "foo" can't be found in the empty string.
> Here is how I ended up with this bug.
> Debugger entered--Lisp error: (error "Regexp cannot match an empty string")
[...]
> command-execute(highlight-regexp)
And this is "not a bug but a feature". This could arguably
be improved. E.g. it should probably call `user-error'.
But highlight-regexp is simply telling you that it's not a good idea to
try to highlight all the empty strings in your buffer: not only there
are many (e.g. as many as point-max), but you wouldn't notice that
they're highlighted anyway.
Stefan
prev parent reply other threads:[~2015-06-14 13:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-13 9:33 bug#20806: 25.0.50; `string-match' is confused??? Vaidheeswaran C
2015-06-13 18:59 ` Vaidheeswaran C
2015-06-14 20:18 ` Stefan Monnier
2015-06-13 19:21 ` Andreas Schwab
2015-06-13 22:58 ` Michael Heerdegen
2015-06-14 13:40 ` Stefan Monnier [this message]
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