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diff --git a/lib/strncasecmp.c b/lib/strncasecmp.c
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+/* strncasecmp.c -- case insensitive string comparator
+ Copyright (C) 1998-1999, 2005-2007, 2009-2022 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include <string.h>
+
+#include <ctype.h>
+#include <limits.h>
+
+#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
+
+/* Compare no more than N bytes of strings S1 and S2, ignoring case,
+ returning less than, equal to or greater than zero if S1 is
+ lexicographically less than, equal to or greater than S2.
+ Note: This function cannot work correctly in multibyte locales. */
+
+int
+strncasecmp (const char *s1, const char *s2, size_t n)
+{
+ register const unsigned char *p1 = (const unsigned char *) s1;
+ register const unsigned char *p2 = (const unsigned char *) s2;
+ unsigned char c1, c2;
+
+ if (p1 == p2 || n == 0)
+ return 0;
+
+ do
+ {
+ c1 = TOLOWER (*p1);
+ c2 = TOLOWER (*p2);
+
+ if (--n == 0 || c1 == '\0')
+ break;
+
+ ++p1;
+ ++p2;
+ }
+ while (c1 == c2);
+
+ if (UCHAR_MAX <= INT_MAX)
+ return c1 - c2;
+ else
+ /* On machines where 'char' and 'int' are types of the same size, the
+ difference of two 'unsigned char' values - including the sign bit -
+ doesn't fit in an 'int'. */
+ return _GL_CMP (c1, c2);
+}