GNU bug report logs - #42522
Emacs 27: 100% CPU when setting mode-name with ligatures

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Package: emacs;

Reported by: Evan Moses <emoses <at> gmail.com>

Date: Fri, 24 Jul 2020 22:30:01 UTC

Severity: normal

Done: Stefan Kangas <stefan <at> marxist.se>

Bug is archived. No further changes may be made.

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From: Robert Pluim <rpluim <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 42522 <at> debbugs.gnu.org, Evan Moses <emoses <at> gmail.com>
Subject: bug#42522: Emacs 27: 100% CPU when setting mode-name with ligatures
Date: Sat, 25 Jul 2020 19:22:19 +0200

>>>>> On Sat, 25 Jul 2020 09:24:47 +0300, Eli Zaretskii <eliz <at> gnu.org> said:

    >> From: Evan Moses <emoses <at> gmail.com>
    >> Date: Fri, 24 Jul 2020 14:35:50 -0700
    >> 
    >> To reproduce, evaluate this
    >> 
    >> (set-char-table-range composition-function-table 47 '([".\\(?:\\(?:\\*\\*\\|//\\|==\\)\\|[*/=>]\\)" 0
    >> font-shape-gstring]))
    >> 
    >> And then evaluate 
    >> 
    >> (setq mode-name "test//")
    >> 
    >> Emacs will become unresponsive and consume 100% CPU.

    Eli> It doesn't hang here.  Could this be macOS-specific?  Or maybe the
    Eli> problem happens only with some fonts?  Does it happen in "emacs -Q"?

I see this on macOS with -Q, which uses Menlo, but only with emacs-27,
not master.. I do see an 'Attempt to shape unibyte text' message from
emacs-27

Robert
This bug report was last modified 4 years and 279 days ago.

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