From: "Mattias Engdegård" <mattiase@acm.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: ture@turepalsson.se, 41445@debbugs.gnu.org
Subject: bug#41445: 26.3; Query-replace triggers "match data clobbered by..."
Date: Sat, 23 May 2020 13:36:37 +0200 [thread overview]
Message-ID: <76CFF420-CB1C-464A-A67C-22D813C00EB8@acm.org> (raw)
In-Reply-To: <83wo542mwz.fsf@gnu.org>
> My line of reasoning was that only the callers of ENCODE_FILE and
> DECODE_FILE will not expect the match-data to be clobbered. Code that
> calls ucs-normalize-region directly may or may not be bothered by the
> clobbering, so we should leave that to the caller.
>
> The advantage of not doing this unconditionally is that we don't
> unnecessarily punishing callers that don't need match-data to be
> saved.
For callers of the ucs-normalize- functions, correctness should come first; their names, semantics or descriptions do not lead the user to suspect them of clobbering the match data. It is an implementation leakage which can be quite unexpected, as is witnessed by this bug.
For example, in one of the few calls I could find at all, this might be classified as a near-miss, only saved by the left-to-right argument evaluation order:
(lookup-new-entry
'regular dictionary (match-string 0)
(ucs-normalize-HFS-NFC-string (match-string 1))))
next prev parent reply other threads:[~2020-05-23 11:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-22 5:07 bug#41445: 26.3; Query-replace triggers "match data clobbered by..." Ture Pålsson
2020-05-22 10:46 ` Mattias Engdegård
2020-05-22 11:11 ` Eli Zaretskii
2020-05-22 11:16 ` Mattias Engdegård
2020-05-22 12:07 ` Eli Zaretskii
2020-05-22 12:21 ` Mattias Engdegård
2020-05-22 12:35 ` Eli Zaretskii
2020-05-23 11:36 ` Mattias Engdegård [this message]
2020-05-23 12:28 ` Eli Zaretskii
2020-05-23 12:37 ` Philipp Stephani
2020-05-23 13:07 ` Eli Zaretskii
2020-05-23 13:08 ` Mattias Engdegård
2020-05-23 13:36 ` Stefan Monnier
2020-05-23 15:43 ` Drew Adams
2020-05-27 14:31 ` Mattias Engdegård
2020-05-27 15:54 ` Eli Zaretskii
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