From 1c04d781195266b6bc88d8a5a584a64aac07f613 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Mon, 10 Jul 2023 13:41:27 +1200
Subject: [PATCH] Don't expose Windows' mbstowcs_l() and wcstombs_l().

Windows has similar functions with leading underscores, and we provided
the rename via a macro in win32_port.h.  In fact its functions are not
always good replacements for the Unix functions, since they can't deal
with UTF-8.  They are only currently used by pg_locale.c, which is
careful to redirect to other Windows routines for UTF-8.  Given that
portability hazard, it seem unlikely to be a good idea to encourage any
other code to think of these functions as being available outside
pg_locale.c.  Any code that thinks it wants these functions probably
wants our wchar2char() or char2wchar() routines instead, or it won't
actually work on Windows in UTF-8 databases.

Furthermore, some major libc implementations including glibc don't have
them (they only have the standard variants without _l), so external code
is very unlikely to require them to exist.

diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index 0eb764e897..61daa8190b 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -154,36 +154,41 @@ static void icu_set_collation_attributes(UCollator *collator, const char *loc,
 										 UErrorCode *status);
 #endif
 
-#ifndef WIN32
 /*
  * POSIX doesn't define _l-variants of these functions, but several systems
- * have them.  We provide our own replacements here.  For Windows, we have
- * macros in win32_port.h.
+ * have them.  We provide our own replacements here.
  */
 #ifndef HAVE_MBSTOWCS_L
 static size_t
 mbstowcs_l(wchar_t *dest, const char *src, size_t n, locale_t loc)
 {
+#ifdef WIN32
+	return _mbstowcs_l(dest, src, n, loc);
+#else
 	size_t		result;
 	locale_t	save_locale = uselocale(loc);
 
 	result = mbstowcs(dest, src, n);
 	uselocale(save_locale);
 	return result;
+#endif
 }
 #endif
 #ifndef HAVE_WCSTOMBS_L
 static size_t
 wcstombs_l(char *dest, const wchar_t *src, size_t n, locale_t loc)
 {
+#ifdef WIN32
+	return _wcstombs_l(dest, src, n, loc);
+#else
 	size_t		result;
 	locale_t	save_locale = uselocale(loc);
 
 	result = wcstombs(dest, src, n);
 	uselocale(save_locale);
 	return result;
-}
 #endif
+}
 #endif
 
 /*
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index b957d5c598..0e6d608330 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -455,8 +455,6 @@ extern int	_pglstat64(const char *name, struct stat *buf);
 #define strcoll_l _strcoll_l
 #define strxfrm_l _strxfrm_l
 #define wcscoll_l _wcscoll_l
-#define wcstombs_l _wcstombs_l
-#define mbstowcs_l _mbstowcs_l
 
 /*
  * Versions of libintl >= 0.18? try to replace setlocale() with a macro
-- 
2.41.0