https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=209352
Bug ID: 209352
Summary: Bug in usr.bin/sed
Product: Base System
Version: 11.0-CURRENT
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: bin
Assignee: freebsd-bugs@FreeBSD.org
Reporter: p...@freebsd.org
This was noted from the openbsd-bugs list :
(Reply from Tim Chase 2016-04-24)...
Can be simplified to the test-case
$ echo a,a,a,a,a | sed -r 's/\<.,/X&/g'
Xa,a,Xa,a,a
$ echo a,a,a,a,a | gsed -r 's/\<.,/X&/g'
Xa,Xa,Xa,Xa,a
It appears the determination of "\<" can get thrown off when the
character preceding it is part of a replacement.
_____
I have reproduced it with the sed in FreeBSD
_____
There is a solution candidate in openbsd-tech, but the patch doesn't apply
directly:
>From Martijn van Duren - 2016-05-04)
For those interested: The problem comes from the fact that the string
pointer increments to the end of the previous match and is then called
with the REG_NOTBOL. The REG_NOTBOL combined with a match at the begin
of the string causes our regex library to treat the word as not begin of
word.
The TRE implementation does the reverse and treats this case as if it
always is begin of word. This causes a similar bug under MacOS:
$ echo 'foo foofoo' | sed -E 's/\<foo/bar/g'
bar barbar
I've solved this problem by converting sed to use REG_STARTEND more
explicitly. Although this isn't a POSIX specified flag, it is already
used by sed and shouldn't be a problem.
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