One of the NetBSD locales is pretty broken. I've reported it to the
NetBSD people. I'm not adding a workaround to gnulib, since the number
of users of this NetBSD locale is probably very small.
2023-04-09 Bruno Haible <br...@clisp.org>
doc: Mention a NetBSD bug.
* doc/posix-functions/towlower.texi: Mention NetBSD bug 57339.
* doc/posix-functions/towupper.texi: Likewise.
diff --git a/doc/posix-functions/towlower.texi
b/doc/posix-functions/towlower.texi
index a53c96f438..a8ef3ce990 100644
--- a/doc/posix-functions/towlower.texi
+++ b/doc/posix-functions/towlower.texi
@@ -23,4 +23,9 @@
@item
On Windows and 32-bit AIX platforms, @code{wchar_t} is a 16-bit type and
therefore cannot
accommodate all Unicode characters.
+@item
+This function returns wrong values even for the ASCII characters
+in a zh_CN.GB18030 locale on some platforms:
+@c https://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=57339
+NetBSD 9.0.
@end itemize
diff --git a/doc/posix-functions/towupper.texi
b/doc/posix-functions/towupper.texi
index 823ff29743..902cf16e68 100644
--- a/doc/posix-functions/towupper.texi
+++ b/doc/posix-functions/towupper.texi
@@ -23,4 +23,9 @@
@item
On Windows and 32-bit AIX platforms, @code{wchar_t} is a 16-bit type and
therefore cannot
accommodate all Unicode characters.
+@item
+This function returns wrong values even for the ASCII characters
+in a zh_CN.GB18030 locale on some platforms:
+@c https://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=57339
+NetBSD 9.0.
@end itemize
