bin/60552: /usr/bin/grep failure under AMD64

>Number:         60552
>Category:       bin
>Synopsis:       /usr/bin/grep failure under AMD64
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Aug 07 12:35:00 +0000 2026
>Originator:     Chavdar Ivanov
>Release:        NetBSD 11 Release
>Organization:
CI4 Consulting Ltd
>Environment:
uname -a
NetBSD netbsd11.lorien.lan 11.0 NetBSD 11.0 (GENERIC) #0: Thu Jul 30 15:23:12 UTC 2026  [email protected]:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
'/usr/bin/grep -i' dumps core going through a file containing UTF16 characters, apparently when one has both -i and --color=auto specified. 

Observed on NetBSD-current from the end of June and on NetBSD-11 Release, only AMD64.

The failure does not occur on NetBSD-current AARCH64.

Initial trace:

#0  0x0000000000e5b468 in prline ()
(gdb) bt
#0  0x0000000000e5b468 in prline ()
#1  0x0000000000e5b8cb in grepbuf ()
#2  0x0000000000e5b988 in grepbuf ()
#3  0x0000000000e5bfff in grepfile ()
#4  0x0000000000e71985 in main ()
>How-To-Repeat:
netbsd11$ echo $LS_COLORS $LSCOLORS

netbsd11$ cat file-with-utf16
Test='∑'
netbsd11$ /usr/bin/grep  -i est file-with-utf16
Test='∑'
netbsd11$ /usr/bin/grep --color=auto   est file-with-utf16
Test='∑'
netbsd11$ /usr/bin/grep --color=auto  -i est file-with-utf16
[1]   Segmentation fault (core dumped) /usr/bin/grep --color=auto -i est file-with-utf16
>Fix:
N/A