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diff --git a/lib/c32width.c b/lib/c32width.c
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+/* Determine the number of screen columns needed for a 32-bit wide character.
+ Copyright (C) 2020-2024 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/>. */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2023. */
+
+#include <config.h>
+
+#define IN_C32WIDTH
+/* Specification. */
+#include <uchar.h>
+
+#include <wchar.h>
+
+#ifdef __CYGWIN__
+# include <cygwin/version.h>
+#endif
+
+#if GNULIB_defined_mbstate_t
+# include "streq.h"
+#endif
+
+#include "localcharset.h"
+
+#if GL_CHAR32_T_IS_UNICODE
+# include "lc-charset-unicode.h"
+#endif
+
+#include "uniwidth.h"
+
+#if _GL_WCHAR_T_IS_UCS4 && !GNULIB_defined_mbstate_t
+_GL_EXTERN_INLINE
+#endif
+int
+c32width (char32_t wc)
+{
+ /* The char32_t encoding of a multibyte character is defined by the way
+ mbrtoc32() is defined. */
+
+#if GNULIB_defined_mbstate_t /* AIX, IRIX */
+ /* mbrtoc32() is defined on top of mbtowc() for the non-UTF-8 locales
+ and directly for the UTF-8 locales. */
+ const char *encoding = locale_charset ();
+ if (STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0))
+ return uc_width (wc, encoding);
+ else
+ return wcwidth (wc);
+
+#elif HAVE_WORKING_MBRTOC32 /* glibc, Android */
+ /* mbrtoc32() is essentially defined by the system libc. */
+
+# if _GL_WCHAR_T_IS_UCS4
+ /* The char32_t encoding of a multibyte character is known to be the same as
+ the wchar_t encoding. */
+ return wcwidth (wc);
+# else
+ /* The char32_t encoding of a multibyte character is known to be UCS-4,
+ different from the wchar_t encoding. */
+ return uc_width (wc, locale_charset ());
+# endif
+
+#elif _GL_SMALL_WCHAR_T /* Cygwin, mingw, MSVC */
+ /* The wchar_t encoding is UTF-16.
+ The char32_t encoding is UCS-4. */
+
+# if defined __CYGWIN__ && CYGWIN_VERSION_DLL_MAJOR >= 1007 && 0
+ /* As an extension to POSIX, the wcwidth() function of Cygwin >= 1.7
+ supports also wc arguments outside the Unicode BMP, that is, outside
+ the 'wchar_t' range. See
+ <https://www.cygwin.com/cgit/newlib-cygwin/commit/?id=098a75dc51caa98f369d98a9809d773bc45329aa>.
+ But the resulting values for these characters are not of good quality. */
+ return wcwidth (wc);
+# else
+ if (wc == (wchar_t) wc)
+ /* wc is in the range for the wcwidth function. */
+ return wcwidth (wc);
+ else
+ return uc_width (wc, locale_charset ());
+# endif
+
+#else /* macOS, FreeBSD, NetBSD, OpenBSD, HP-UX, Solaris, Minix, Android */
+ /* char32_t and wchar_t are equivalent. */
+ static_assert (sizeof (char32_t) == sizeof (wchar_t));
+
+# if GL_CHAR32_T_IS_UNICODE && GL_CHAR32_T_VS_WCHAR_T_NEEDS_CONVERSION
+ return uc_width (wc, locale_charset ());
+# endif
+ return wcwidth (wc);
+#endif
+}