GNU bug report logs -
#23917
25.0.95; commit 3a9d6296b35e5317c497674d5725eb52699bd3b8 causing org-capture to error out
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Reported by: Robert Pluim <rpluim <at> gmail.com>
Date: Fri, 8 Jul 2016 12:43:02 UTC
Severity: normal
Tags: fixed
Found in version 25.0.95
Fixed in version 25.1
Done: npostavs <at> users.sourceforge.net
Bug is archived. No further changes may be made.
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> From: Stefan Monnier <monnier <at> iro.umontreal.ca>
> Cc: Robert Pluim <rpluim <at> gmail.com>, 23917 <at> debbugs.gnu.org, alex.bennee <at> linaro.org, jwiegley <at> gmail.com, nljlistbox2 <at> gmail.com
> Date: Mon, 18 Jul 2016 20:58:35 -0400
>
> > In the case in point, a single character at EOB (= 62) was deleted,
> > which made EOB be 61, one less than its previous value. When
> > save-match-data was called from within a hook set up by Org, it tried
> > to record the end of the sub-expression as 62, but set-marker silently
> > changed that to 61. That "corrected" value was subsequently restored
> > when save-match-data was exited, whereas replace-match expected to see
> > the original value of 62, and therefore barfed.
>
> I think this change performed by save-match-data is harmless: the old
> value (62) was not valid any more anyway.
In this particular case, yes. But only in this case, because (a)
there's actually only one sub-expression, and (b) it ends exactly at
EOB.
The more general problem is when there's at least one more
sub-expression, whose start and/or end are after the new EOB. Those
sub-expression's data will be completely bogus after the adjustment,
should the buffer-modification hooks use save-match-data.
> So I think a safe fix is to try and relax the check we added to
> replace-match so it doesn't get all worked up when something ā„ EOB gets
> changed to something else that's also ā„ EOB.
And lose the other sub-expressions in a more general case? Really?
> Or maybe instead of signaling an error, we could simply skip the "Adjust
> search data for this change".
That would still sweep the problem under the carpet, leaving the match
data bogus, so I don't like doing that.
> This said, I don't fully understand what's going on: bug#23869 reported
> a crash, but AFAICT the match-data here is only used to adjust
> search_regs which seems like it wouldn't cause a crash, even if the new
> values are bogus.
The crash in bug#23869 was due to this:
newpoint = search_regs.start[sub] + SCHARS (newtext);
[...]
/* Now move point "officially" to the start of the inserted replacement. */
move_if_not_intangible (newpoint); <<<<<<<<<<<<<<<<<<<<<<<
because due to clobbering, newpoint became -1.
> > - '((save-match-data-internal (match-data)))
> > + '((save-match-data-internal (match-data 'integers)))
>
> That looks risky.
Then how about manually doing the equivalent of save-match-data around
the call to replace_range, calling match-data with non-nil argument?
This bug report was last modified 8 years and 303 days ago.
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