check_strxfrm_bug()

From 87268870aa9b6f22eb0bf831614bd38c529b0c8c Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Wed, 28 Jun 2023 10:23:32 +1200
Subject: [PATCH] All supported computers have locale_t.

locale_t is defined by POSIX:1-2008 and SUSv4, and available on all
targeted systems.

Definitions for HAVE_WCSTOMBS_L and HAVE_MBSTOWCS_L had to be moved into
win32_port.h, because this change revealed that MinGW builds on Windows
were failing to detect these functions, but without them we couldn't
build due to the assumption that uselocale() exists.

Discussion: https://postgr.es/m/CA%2BhUKGLg7_T2GKwZFAkEf0V7vbnur-NfCjZPKZb%3DZfAXSV1ORw%40mail.gmail.com

diff --git a/config/c-library.m4 b/config/c-library.m4
index c1dd804679..aa8223d2ef 100644
--- a/config/c-library.m4
+++ b/config/c-library.m4
@@ -86,9 +86,9 @@ AC_DEFUN([PGAC_STRUCT_SOCKADDR_SA_LEN],
 # PGAC_TYPE_LOCALE_T
 # ------------------
 # Check for the locale_t type and find the right header file.  macOS
-# needs xlocale.h; standard is locale.h, but glibc also has an
-# xlocale.h file that we should not use.
-#
+# needs xlocale.h; standard is locale.h, but glibc <= 2.25 also had an
+# xlocale.h file that we should not use, so we check the standard
+# header first.
 AC_DEFUN([PGAC_TYPE_LOCALE_T],
 [AC_CACHE_CHECK([for locale_t], pgac_cv_type_locale_t,
 [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
@@ -102,10 +102,6 @@ locale_t x;],
 [])],
 [pgac_cv_type_locale_t='yes (in xlocale.h)'],
 [pgac_cv_type_locale_t=no])])])
-if test "$pgac_cv_type_locale_t" != no; then
-  AC_DEFINE(HAVE_LOCALE_T, 1,
-            [Define to 1 if the system has the type `locale_t'.])
-fi
 if test "$pgac_cv_type_locale_t" = 'yes (in xlocale.h)'; then
   AC_DEFINE(LOCALE_T_IN_XLOCALE, 1,
             [Define to 1 if `locale_t' requires <xlocale.h>.])
diff --git a/configure b/configure
index a1c3cb0036..b8bc03e2c7 100755
--- a/configure
+++ b/configure
@@ -15122,11 +15122,6 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_type_locale_t" >&5
 $as_echo "$pgac_cv_type_locale_t" >&6; }
-if test "$pgac_cv_type_locale_t" != no; then
-
-$as_echo "#define HAVE_LOCALE_T 1" >>confdefs.h
-
-fi
 if test "$pgac_cv_type_locale_t" = 'yes (in xlocale.h)'; then
 
 $as_echo "#define LOCALE_T_IN_XLOCALE 1" >>confdefs.h
diff --git a/meson.build b/meson.build
index 7bc7310c44..7cc4cbc034 100644
--- a/meson.build
+++ b/meson.build
@@ -2283,17 +2283,12 @@ else
   cdata.set('STRERROR_R_INT', false)
 endif
 
-# Check for the locale_t type and find the right header file.  macOS
-# needs xlocale.h; standard is locale.h, but glibc also has an
+# Find the right header file for the locale_t type.  macOS
+# needs xlocale.h; standard is locale.h, but older glibc also had an
 # xlocale.h file that we should not use.  MSVC has a replacement
 # defined in src/include/port/win32_port.h.
-if cc.has_type('locale_t', prefix: '#include <locale.h>')
-  cdata.set('HAVE_LOCALE_T', 1)
-elif cc.has_type('locale_t', prefix: '#include <xlocale.h>')
-  cdata.set('HAVE_LOCALE_T', 1)
+if not cc.has_type('locale_t', prefix: '#include <locale.h>') and cc.has_type('locale_t', prefix: '#include <xlocale.h>')
   cdata.set('LOCALE_T_IN_XLOCALE', 1)
-elif cc.get_id() == 'msvc'
-  cdata.set('HAVE_LOCALE_T', 1)
 endif
 
 # Check if the C compiler understands typeof or a variant.  Define
@@ -2489,13 +2484,6 @@ if cc.has_function('syslog', args: test_c_args) and \
 endif
 
 
-# MSVC has replacements defined in src/include/port/win32_port.h.
-if cc.get_id() == 'msvc'
-  cdata.set('HAVE_WCSTOMBS_L', 1)
-  cdata.set('HAVE_MBSTOWCS_L', 1)
-endif
-
-
 # if prerequisites for unnamed posix semas aren't fulfilled, fall back to sysv
 # semaphores
 if sema_kind == 'unnamed_posix' and \
diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index efb8b4d289..cc239b4d14 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -534,7 +534,7 @@ pg_collation_actual_version(PG_FUNCTION_ARGS)
 
 
 /* will we use "locale -a" in pg_import_system_collations? */
-#if defined(HAVE_LOCALE_T) && !defined(WIN32)
+#if !defined(WIN32)
 #define READ_LOCALE_A_OUTPUT
 #endif
 
diff --git a/src/backend/regex/regc_pg_locale.c b/src/backend/regex/regc_pg_locale.c
index 00ce735fdd..31e6300b5d 100644
--- a/src/backend/regex/regc_pg_locale.c
+++ b/src/backend/regex/regc_pg_locale.c
@@ -44,8 +44,7 @@
  * the platform's wchar_t representation matches what we do in pg_wchar
  * conversions.
  *
- * 3. Other collations are only supported on platforms that HAVE_LOCALE_T.
- * Here, we use the locale_t-extended forms of the <wctype.h> and <ctype.h>
+ * 3. Here, we use the locale_t-extended forms of the <wctype.h> and <ctype.h>
  * functions, under exactly the same cases as #2.
  *
  * There is one notable difference between cases 2 and 3: in the "default"
@@ -252,11 +251,6 @@ pg_set_regex_collation(Oid collation)
 	}
 	else
 	{
-		/*
-		 * NB: pg_newlocale_from_collation will fail if not HAVE_LOCALE_T; the
-		 * case of pg_regex_locale != 0 but not HAVE_LOCALE_T does not have to
-		 * be considered below.
-		 */
 		pg_regex_locale = pg_newlocale_from_collation(collation);
 
 		if (!pg_locale_deterministic(pg_regex_locale))
@@ -304,16 +298,12 @@ pg_wc_isdigit(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isdigit((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswdigit_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isdigit_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -340,16 +330,12 @@ pg_wc_isalpha(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalpha((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalpha_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalpha_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -376,16 +362,12 @@ pg_wc_isalnum(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalnum((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalnum_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalnum_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -421,16 +403,12 @@ pg_wc_isupper(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isupper((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswupper_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isupper_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -457,16 +435,12 @@ pg_wc_islower(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					islower((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswlower_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					islower_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -493,16 +467,12 @@ pg_wc_isgraph(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isgraph((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswgraph_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isgraph_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -529,16 +499,12 @@ pg_wc_isprint(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isprint((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswprint_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isprint_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -565,16 +531,12 @@ pg_wc_ispunct(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					ispunct((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswpunct_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					ispunct_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -601,16 +563,12 @@ pg_wc_isspace(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isspace((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswspace_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isspace_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -645,16 +603,12 @@ pg_wc_toupper(pg_wchar c)
 				return toupper((unsigned char) c);
 			return c;
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return towupper_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			if (c <= (pg_wchar) UCHAR_MAX)
 				return toupper_l((unsigned char) c, pg_regex_locale->info.lt);
-#endif
 			return c;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -689,16 +643,12 @@ pg_wc_tolower(pg_wchar c)
 				return tolower((unsigned char) c);
 			return c;
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return towlower_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			if (c <= (pg_wchar) UCHAR_MAX)
 				return tolower_l((unsigned char) c, pg_regex_locale->info.lt);
-#endif
 			return c;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index e6246dc44b..e27ea8ef97 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -1613,12 +1613,6 @@ u_strToTitle_default_BI(UChar *dest, int32_t destCapacity,
  * in multibyte character sets.  Note that in either case we are effectively
  * assuming that the database character encoding matches the encoding implied
  * by LC_CTYPE.
- *
- * If the system provides locale_t and associated functions (which are
- * standardized by Open Group's XBD), we can support collations that are
- * neither default nor C.  The code is written to handle both combinations
- * of have-wide-characters and have-locale_t, though it's rather unlikely
- * a platform would have the latter without the former.
  */
 
 /*
@@ -1696,11 +1690,9 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						workspace[curr_char] = towlower_l(workspace[curr_char], mylocale->info.lt);
 					else
-#endif
 						workspace[curr_char] = towlower(workspace[curr_char]);
 				}
 
@@ -1729,11 +1721,9 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						*p = tolower_l((unsigned char) *p, mylocale->info.lt);
 					else
-#endif
 						*p = pg_tolower((unsigned char) *p);
 				}
 			}
@@ -1818,11 +1808,9 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						workspace[curr_char] = towupper_l(workspace[curr_char], mylocale->info.lt);
 					else
-#endif
 						workspace[curr_char] = towupper(workspace[curr_char]);
 				}
 
@@ -1851,11 +1839,9 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						*p = toupper_l((unsigned char) *p, mylocale->info.lt);
 					else
-#endif
 						*p = pg_toupper((unsigned char) *p);
 				}
 			}
@@ -1941,7 +1927,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 					{
 						if (wasalnum)
@@ -1951,7 +1936,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 						wasalnum = iswalnum_l(workspace[curr_char], mylocale->info.lt);
 					}
 					else
-#endif
 					{
 						if (wasalnum)
 							workspace[curr_char] = towlower(workspace[curr_char]);
@@ -1986,7 +1970,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 					{
 						if (wasalnum)
@@ -1996,7 +1979,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 						wasalnum = isalnum_l((unsigned char) *p, mylocale->info.lt);
 					}
 					else
-#endif
 					{
 						if (wasalnum)
 							*p = pg_tolower((unsigned char) *p);
diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index 33a2f46aab..62902caefa 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -95,10 +95,8 @@ SB_lower_char(unsigned char c, pg_locale_t locale, bool locale_is_c)
 {
 	if (locale_is_c)
 		return pg_ascii_tolower(c);
-#ifdef HAVE_LOCALE_T
 	else if (locale)
 		return tolower_l(c, locale->info.lt);
-#endif
 	else
 		return pg_tolower(c);
 }
diff --git a/src/backend/utils/adt/like_support.c b/src/backend/utils/adt/like_support.c
index 9b603d42f3..34e1b709ae 100644
--- a/src/backend/utils/adt/like_support.c
+++ b/src/backend/utils/adt/like_support.c
@@ -1509,10 +1509,8 @@ pattern_char_isalpha(char c, bool is_multibyte,
 	else if (locale && locale->provider == COLLPROVIDER_ICU)
 		return IS_HIGHBIT_SET(c) ||
 			(c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
-#ifdef HAVE_LOCALE_T
 	else if (locale && locale->provider == COLLPROVIDER_LIBC)
 		return isalpha_l((unsigned char) c, locale->info.lt);
-#endif
 	else
 		return isalpha((unsigned char) c);
 }
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index c8b36f3af2..83c5b960a7 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -1420,7 +1420,6 @@ make_icu_collator(const char *iculocstr,
 
 
 /* simple subroutine for reporting errors from newlocale() */
-#ifdef HAVE_LOCALE_T
 static void
 report_newlocale_failure(const char *localename)
 {
@@ -1449,7 +1448,6 @@ report_newlocale_failure(const char *localename)
 			  errdetail("The operating system could not find any locale data for the locale name \"%s\".",
 						localename) : 0)));
 }
-#endif							/* HAVE_LOCALE_T */
 
 bool
 pg_locale_deterministic(pg_locale_t locale)
@@ -1466,10 +1464,6 @@ pg_locale_deterministic(pg_locale_t locale)
  * lifetime of the backend.  Thus, do not free the result with freelocale().
  *
  * As a special optimization, the default/database collation returns 0.
- * Callers should then revert to the non-locale_t-enabled code path.
- * Also, callers should avoid calling this before going down a C/POSIX
- * fastpath, because such a fastpath should work even on platforms without
- * locale_t support in the C library.
  *
  * For simplicity, we always generate COLLATE + CTYPE even though we
  * might only need one of them.  Since this is called only once per session,
@@ -1515,7 +1509,6 @@ pg_newlocale_from_collation(Oid collid)
 
 		if (collform->collprovider == COLLPROVIDER_LIBC)
 		{
-#ifdef HAVE_LOCALE_T
 			const char *collcollate;
 			const char *collctype pg_attribute_unused();
 			locale_t	loc;
@@ -1566,12 +1559,6 @@ pg_newlocale_from_collation(Oid collid)
 			}
 
 			result.info.lt = loc;
-#else							/* not HAVE_LOCALE_T */
-			/* platform that doesn't support locale_t */
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("collation provider LIBC is not supported on this platform")));
-#endif							/* not HAVE_LOCALE_T */
 		}
 		else if (collform->collprovider == COLLPROVIDER_ICU)
 		{
@@ -1788,11 +1775,9 @@ pg_strncoll_libc_win32_utf8(const char *arg1, size_t len1, const char *arg2,
 	((LPWSTR) a2p)[r] = 0;
 
 	errno = 0;
-#ifdef HAVE_LOCALE_T
 	if (locale)
 		result = wcscoll_l((LPWSTR) a1p, (LPWSTR) a2p, locale->info.lt);
 	else
-#endif
 		result = wcscoll((LPWSTR) a1p, (LPWSTR) a2p);
 	if (result == 2147483647)	/* _NLSCMPERROR; missing from mingw headers */
 		ereport(ERROR,
@@ -1831,14 +1816,7 @@ pg_strcoll_libc(const char *arg1, const char *arg2, pg_locale_t locale)
 	else
 #endif							/* WIN32 */
 	if (locale)
-	{
-#ifdef HAVE_LOCALE_T
 		result = strcoll_l(arg1, arg2, locale->info.lt);
-#else
-		/* shouldn't happen */
-		elog(ERROR, "unsupported collprovider: %c", locale->provider);
-#endif
-	}
 	else
 		result = strcoll(arg1, arg2);
 
@@ -2065,11 +2043,9 @@ pg_strxfrm_libc(char *dest, const char *src, size_t destsize,
 	Assert(!locale || locale->provider == COLLPROVIDER_LIBC);
 
 #ifdef TRUST_STRXFRM
-#ifdef HAVE_LOCALE_T
 	if (locale)
 		return strxfrm_l(dest, src, destsize, locale->info.lt);
 	else
-#endif
 		return strxfrm(dest, src, destsize);
 #else
 	/* shouldn't happen */
@@ -2955,7 +2931,6 @@ wchar2char(char *to, const wchar_t *from, size_t tolen, pg_locale_t locale)
 	}
 	else
 	{
-#ifdef HAVE_LOCALE_T
 #ifdef HAVE_WCSTOMBS_L
 		/* Use wcstombs_l for nondefault locales */
 		result = wcstombs_l(to, from, tolen, locale->info.lt);
@@ -2967,11 +2942,6 @@ wchar2char(char *to, const wchar_t *from, size_t tolen, pg_locale_t locale)
 
 		uselocale(save_locale);
 #endif							/* HAVE_WCSTOMBS_L */
-#else							/* !HAVE_LOCALE_T */
-		/* Can't have locale != 0 without HAVE_LOCALE_T */
-		elog(ERROR, "wcstombs_l is not available");
-		result = 0;				/* keep compiler quiet */
-#endif							/* HAVE_LOCALE_T */
 	}
 
 	return result;
@@ -3032,7 +3002,6 @@ char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
 		}
 		else
 		{
-#ifdef HAVE_LOCALE_T
 #ifdef HAVE_MBSTOWCS_L
 			/* Use mbstowcs_l for nondefault locales */
 			result = mbstowcs_l(to, str, tolen, locale->info.lt);
@@ -3044,11 +3013,6 @@ char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
 
 			uselocale(save_locale);
 #endif							/* HAVE_MBSTOWCS_L */
-#else							/* !HAVE_LOCALE_T */
-			/* Can't have locale != 0 without HAVE_LOCALE_T */
-			elog(ERROR, "mbstowcs_l is not available");
-			result = 0;			/* keep compiler quiet */
-#endif							/* HAVE_LOCALE_T */
 		}
 
 		pfree(str);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 6d572c3820..c33fc4b8cd 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -298,9 +298,6 @@
 /* Define to 1 if you have the `zstd' library (-lzstd). */
 #undef HAVE_LIBZSTD
 
-/* Define to 1 if the system has the type `locale_t'. */
-#undef HAVE_LOCALE_T
-
 /* Define to 1 if `long int' works and is 64 bits. */
 #undef HAVE_LONG_INT_64
 
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index b957d5c598..dee85fa3b2 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -458,6 +458,9 @@ extern int	_pglstat64(const char *name, struct stat *buf);
 #define wcstombs_l _wcstombs_l
 #define mbstowcs_l _mbstowcs_l
 
+#define HAVE_WCSTOMBS_L 1
+#define HAVE_MBSTOWCS_L 1
+
 /*
  * Versions of libintl >= 0.18? try to replace setlocale() with a macro
  * to their own versions.  Remove the macro, if it exists, because it
diff --git a/src/include/utils/pg_locale.h b/src/include/utils/pg_locale.h
index e2a7243542..6447bea8e0 100644
--- a/src/include/utils/pg_locale.h
+++ b/src/include/utils/pg_locale.h
@@ -67,9 +67,7 @@ extern void cache_locale_time(void);
 
 
 /*
- * We define our own wrapper around locale_t so we can keep the same
- * function signatures for all builds, while not having to create a
- * fake version of the standard type locale_t in the global namespace.
+ * We use a discriminated union to hold either a locale_t or an ICU collator.
  * pg_locale_t is occasionally checked for truth, so make it a pointer.
  */
 struct pg_locale_struct
@@ -78,9 +76,7 @@ struct pg_locale_struct
 	bool		deterministic;
 	union
 	{
-#ifdef HAVE_LOCALE_T
 		locale_t	lt;
-#endif
 #ifdef USE_ICU
 		struct
 		{
@@ -88,7 +84,6 @@ struct pg_locale_struct
 			UCollator  *ucol;
 		}			icu;
 #endif
-		int			dummy;		/* in case we have neither LOCALE_T nor ICU */
 	}			info;
 };
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index b6d31c3583..bf708f15b3 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -296,7 +296,6 @@ sub GenerateFiles
 		HAVE_LIBXSLT => undef,
 		HAVE_LIBZ => $self->{options}->{zlib} ? 1 : undef,
 		HAVE_LIBZSTD => undef,
-		HAVE_LOCALE_T => 1,
 		HAVE_LONG_INT_64 => undef,
 		HAVE_LONG_LONG_INT_64 => 1,
 		HAVE_MBARRIER_H => undef,
-- 
2.39.2

From ab0705a9e169627a77bf4e3cc36ea53603162921 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Tue, 4 Jul 2023 16:32:35 +1200
Subject: [PATCH v2] All supported systems have locale_t.

locale_t is defined by POSIX.1-2008 and SUSv4, and available on all
targeted systems.  For Windows, win32_port.h redirects to a partial
implementation called _locale_t.  It's time to remove a lot of
compile-time tests for HAVE_LOCALE_T, and a few associated comments and
dead code branches.

Definitions for HAVE_WCSTOMBS_L and HAVE_MBSTOWCS_L had to be moved into
win32_port.h, because this change revealed that MinGW builds on Windows
were failing to detect these functions, but without them we couldn't
build due to the assumption that uselocale() exists.

Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Tristan Partin <tristan@neon.tech>
Discussion: https://postgr.es/m/CA%2BhUKGLg7_T2GKwZFAkEf0V7vbnur-NfCjZPKZb%3DZfAXSV1ORw%40mail.gmail.com
---
 config/c-library.m4                  | 10 ++----
 configure                            |  5 ---
 meson.build                          | 22 +++---------
 src/backend/commands/collationcmds.c |  2 +-
 src/backend/regex/regc_pg_locale.c   | 52 +---------------------------
 src/backend/utils/adt/formatting.c   | 18 ----------
 src/backend/utils/adt/like.c         |  2 --
 src/backend/utils/adt/like_support.c |  2 --
 src/backend/utils/adt/pg_locale.c    | 36 -------------------
 src/include/pg_config.h.in           |  3 --
 src/include/port/win32_port.h        |  3 ++
 src/include/utils/pg_locale.h        |  7 +---
 src/tools/msvc/Solution.pm           |  5 ++-
 13 files changed, 16 insertions(+), 151 deletions(-)

diff --git a/config/c-library.m4 b/config/c-library.m4
index c1dd804679..aa8223d2ef 100644
--- a/config/c-library.m4
+++ b/config/c-library.m4
@@ -86,9 +86,9 @@ AC_DEFUN([PGAC_STRUCT_SOCKADDR_SA_LEN],
 # PGAC_TYPE_LOCALE_T
 # ------------------
 # Check for the locale_t type and find the right header file.  macOS
-# needs xlocale.h; standard is locale.h, but glibc also has an
-# xlocale.h file that we should not use.
-#
+# needs xlocale.h; standard is locale.h, but glibc <= 2.25 also had an
+# xlocale.h file that we should not use, so we check the standard
+# header first.
 AC_DEFUN([PGAC_TYPE_LOCALE_T],
 [AC_CACHE_CHECK([for locale_t], pgac_cv_type_locale_t,
 [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
@@ -102,10 +102,6 @@ locale_t x;],
 [])],
 [pgac_cv_type_locale_t='yes (in xlocale.h)'],
 [pgac_cv_type_locale_t=no])])])
-if test "$pgac_cv_type_locale_t" != no; then
-  AC_DEFINE(HAVE_LOCALE_T, 1,
-            [Define to 1 if the system has the type `locale_t'.])
-fi
 if test "$pgac_cv_type_locale_t" = 'yes (in xlocale.h)'; then
   AC_DEFINE(LOCALE_T_IN_XLOCALE, 1,
             [Define to 1 if `locale_t' requires <xlocale.h>.])
diff --git a/configure b/configure
index 997d42d8f7..f1d4630007 100755
--- a/configure
+++ b/configure
@@ -15120,11 +15120,6 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_type_locale_t" >&5
 $as_echo "$pgac_cv_type_locale_t" >&6; }
-if test "$pgac_cv_type_locale_t" != no; then
-
-$as_echo "#define HAVE_LOCALE_T 1" >>confdefs.h
-
-fi
 if test "$pgac_cv_type_locale_t" = 'yes (in xlocale.h)'; then
 
 $as_echo "#define LOCALE_T_IN_XLOCALE 1" >>confdefs.h
diff --git a/meson.build b/meson.build
index 3ea4b0d72a..82a966fcc2 100644
--- a/meson.build
+++ b/meson.build
@@ -2283,17 +2283,12 @@ else
   cdata.set('STRERROR_R_INT', false)
 endif
 
-# Check for the locale_t type and find the right header file.  macOS
-# needs xlocale.h; standard is locale.h, but glibc also has an
-# xlocale.h file that we should not use.  MSVC has a replacement
-# defined in src/include/port/win32_port.h.
-if cc.has_type('locale_t', prefix: '#include <locale.h>')
-  cdata.set('HAVE_LOCALE_T', 1)
-elif cc.has_type('locale_t', prefix: '#include <xlocale.h>')
-  cdata.set('HAVE_LOCALE_T', 1)
+# Find the right header file for the locale_t type.  macOS needs xlocale.h;
+# standard is locale.h, but glibc <= 2.25 also had an xlocale.h file that
+# we should not use so we check the standard header first.  MSVC has a
+# replacement defined in src/include/port/win32_port.h.
+if not cc.has_type('locale_t', prefix: '#include <locale.h>') and cc.has_type('locale_t', prefix: '#include <xlocale.h>')
   cdata.set('LOCALE_T_IN_XLOCALE', 1)
-elif cc.get_id() == 'msvc'
-  cdata.set('HAVE_LOCALE_T', 1)
 endif
 
 # Check if the C compiler understands typeof or a variant.  Define
@@ -2489,13 +2484,6 @@ if cc.has_function('syslog', args: test_c_args) and \
 endif
 
 
-# MSVC has replacements defined in src/include/port/win32_port.h.
-if cc.get_id() == 'msvc'
-  cdata.set('HAVE_WCSTOMBS_L', 1)
-  cdata.set('HAVE_MBSTOWCS_L', 1)
-endif
-
-
 # if prerequisites for unnamed posix semas aren't fulfilled, fall back to sysv
 # semaphores
 if sema_kind == 'unnamed_posix' and \
diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index efb8b4d289..cc239b4d14 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -534,7 +534,7 @@ pg_collation_actual_version(PG_FUNCTION_ARGS)
 
 
 /* will we use "locale -a" in pg_import_system_collations? */
-#if defined(HAVE_LOCALE_T) && !defined(WIN32)
+#if !defined(WIN32)
 #define READ_LOCALE_A_OUTPUT
 #endif
 
diff --git a/src/backend/regex/regc_pg_locale.c b/src/backend/regex/regc_pg_locale.c
index 00ce735fdd..31e6300b5d 100644
--- a/src/backend/regex/regc_pg_locale.c
+++ b/src/backend/regex/regc_pg_locale.c
@@ -44,8 +44,7 @@
  * the platform's wchar_t representation matches what we do in pg_wchar
  * conversions.
  *
- * 3. Other collations are only supported on platforms that HAVE_LOCALE_T.
- * Here, we use the locale_t-extended forms of the <wctype.h> and <ctype.h>
+ * 3. Here, we use the locale_t-extended forms of the <wctype.h> and <ctype.h>
  * functions, under exactly the same cases as #2.
  *
  * There is one notable difference between cases 2 and 3: in the "default"
@@ -252,11 +251,6 @@ pg_set_regex_collation(Oid collation)
 	}
 	else
 	{
-		/*
-		 * NB: pg_newlocale_from_collation will fail if not HAVE_LOCALE_T; the
-		 * case of pg_regex_locale != 0 but not HAVE_LOCALE_T does not have to
-		 * be considered below.
-		 */
 		pg_regex_locale = pg_newlocale_from_collation(collation);
 
 		if (!pg_locale_deterministic(pg_regex_locale))
@@ -304,16 +298,12 @@ pg_wc_isdigit(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isdigit((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswdigit_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isdigit_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -340,16 +330,12 @@ pg_wc_isalpha(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalpha((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalpha_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalpha_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -376,16 +362,12 @@ pg_wc_isalnum(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalnum((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalnum_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalnum_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -421,16 +403,12 @@ pg_wc_isupper(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isupper((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswupper_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isupper_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -457,16 +435,12 @@ pg_wc_islower(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					islower((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswlower_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					islower_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -493,16 +467,12 @@ pg_wc_isgraph(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isgraph((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswgraph_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isgraph_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -529,16 +499,12 @@ pg_wc_isprint(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isprint((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswprint_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isprint_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -565,16 +531,12 @@ pg_wc_ispunct(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					ispunct((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswpunct_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					ispunct_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -601,16 +563,12 @@ pg_wc_isspace(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isspace((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswspace_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isspace_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -645,16 +603,12 @@ pg_wc_toupper(pg_wchar c)
 				return toupper((unsigned char) c);
 			return c;
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return towupper_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			if (c <= (pg_wchar) UCHAR_MAX)
 				return toupper_l((unsigned char) c, pg_regex_locale->info.lt);
-#endif
 			return c;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -689,16 +643,12 @@ pg_wc_tolower(pg_wchar c)
 				return tolower((unsigned char) c);
 			return c;
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return towlower_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			if (c <= (pg_wchar) UCHAR_MAX)
 				return tolower_l((unsigned char) c, pg_regex_locale->info.lt);
-#endif
 			return c;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index e6246dc44b..e27ea8ef97 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -1613,12 +1613,6 @@ u_strToTitle_default_BI(UChar *dest, int32_t destCapacity,
  * in multibyte character sets.  Note that in either case we are effectively
  * assuming that the database character encoding matches the encoding implied
  * by LC_CTYPE.
- *
- * If the system provides locale_t and associated functions (which are
- * standardized by Open Group's XBD), we can support collations that are
- * neither default nor C.  The code is written to handle both combinations
- * of have-wide-characters and have-locale_t, though it's rather unlikely
- * a platform would have the latter without the former.
  */
 
 /*
@@ -1696,11 +1690,9 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						workspace[curr_char] = towlower_l(workspace[curr_char], mylocale->info.lt);
 					else
-#endif
 						workspace[curr_char] = towlower(workspace[curr_char]);
 				}
 
@@ -1729,11 +1721,9 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						*p = tolower_l((unsigned char) *p, mylocale->info.lt);
 					else
-#endif
 						*p = pg_tolower((unsigned char) *p);
 				}
 			}
@@ -1818,11 +1808,9 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						workspace[curr_char] = towupper_l(workspace[curr_char], mylocale->info.lt);
 					else
-#endif
 						workspace[curr_char] = towupper(workspace[curr_char]);
 				}
 
@@ -1851,11 +1839,9 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						*p = toupper_l((unsigned char) *p, mylocale->info.lt);
 					else
-#endif
 						*p = pg_toupper((unsigned char) *p);
 				}
 			}
@@ -1941,7 +1927,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 					{
 						if (wasalnum)
@@ -1951,7 +1936,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 						wasalnum = iswalnum_l(workspace[curr_char], mylocale->info.lt);
 					}
 					else
-#endif
 					{
 						if (wasalnum)
 							workspace[curr_char] = towlower(workspace[curr_char]);
@@ -1986,7 +1970,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 					{
 						if (wasalnum)
@@ -1996,7 +1979,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 						wasalnum = isalnum_l((unsigned char) *p, mylocale->info.lt);
 					}
 					else
-#endif
 					{
 						if (wasalnum)
 							*p = pg_tolower((unsigned char) *p);
diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index 33a2f46aab..62902caefa 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -95,10 +95,8 @@ SB_lower_char(unsigned char c, pg_locale_t locale, bool locale_is_c)
 {
 	if (locale_is_c)
 		return pg_ascii_tolower(c);
-#ifdef HAVE_LOCALE_T
 	else if (locale)
 		return tolower_l(c, locale->info.lt);
-#endif
 	else
 		return pg_tolower(c);
 }
diff --git a/src/backend/utils/adt/like_support.c b/src/backend/utils/adt/like_support.c
index 9b603d42f3..34e1b709ae 100644
--- a/src/backend/utils/adt/like_support.c
+++ b/src/backend/utils/adt/like_support.c
@@ -1509,10 +1509,8 @@ pattern_char_isalpha(char c, bool is_multibyte,
 	else if (locale && locale->provider == COLLPROVIDER_ICU)
 		return IS_HIGHBIT_SET(c) ||
 			(c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
-#ifdef HAVE_LOCALE_T
 	else if (locale && locale->provider == COLLPROVIDER_LIBC)
 		return isalpha_l((unsigned char) c, locale->info.lt);
-#endif
 	else
 		return isalpha((unsigned char) c);
 }
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index c8b36f3af2..83c5b960a7 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -1420,7 +1420,6 @@ make_icu_collator(const char *iculocstr,
 
 
 /* simple subroutine for reporting errors from newlocale() */
-#ifdef HAVE_LOCALE_T
 static void
 report_newlocale_failure(const char *localename)
 {
@@ -1449,7 +1448,6 @@ report_newlocale_failure(const char *localename)
 			  errdetail("The operating system could not find any locale data for the locale name \"%s\".",
 						localename) : 0)));
 }
-#endif							/* HAVE_LOCALE_T */
 
 bool
 pg_locale_deterministic(pg_locale_t locale)
@@ -1466,10 +1464,6 @@ pg_locale_deterministic(pg_locale_t locale)
  * lifetime of the backend.  Thus, do not free the result with freelocale().
  *
  * As a special optimization, the default/database collation returns 0.
- * Callers should then revert to the non-locale_t-enabled code path.
- * Also, callers should avoid calling this before going down a C/POSIX
- * fastpath, because such a fastpath should work even on platforms without
- * locale_t support in the C library.
  *
  * For simplicity, we always generate COLLATE + CTYPE even though we
  * might only need one of them.  Since this is called only once per session,
@@ -1515,7 +1509,6 @@ pg_newlocale_from_collation(Oid collid)
 
 		if (collform->collprovider == COLLPROVIDER_LIBC)
 		{
-#ifdef HAVE_LOCALE_T
 			const char *collcollate;
 			const char *collctype pg_attribute_unused();
 			locale_t	loc;
@@ -1566,12 +1559,6 @@ pg_newlocale_from_collation(Oid collid)
 			}
 
 			result.info.lt = loc;
-#else							/* not HAVE_LOCALE_T */
-			/* platform that doesn't support locale_t */
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("collation provider LIBC is not supported on this platform")));
-#endif							/* not HAVE_LOCALE_T */
 		}
 		else if (collform->collprovider == COLLPROVIDER_ICU)
 		{
@@ -1788,11 +1775,9 @@ pg_strncoll_libc_win32_utf8(const char *arg1, size_t len1, const char *arg2,
 	((LPWSTR) a2p)[r] = 0;
 
 	errno = 0;
-#ifdef HAVE_LOCALE_T
 	if (locale)
 		result = wcscoll_l((LPWSTR) a1p, (LPWSTR) a2p, locale->info.lt);
 	else
-#endif
 		result = wcscoll((LPWSTR) a1p, (LPWSTR) a2p);
 	if (result == 2147483647)	/* _NLSCMPERROR; missing from mingw headers */
 		ereport(ERROR,
@@ -1831,14 +1816,7 @@ pg_strcoll_libc(const char *arg1, const char *arg2, pg_locale_t locale)
 	else
 #endif							/* WIN32 */
 	if (locale)
-	{
-#ifdef HAVE_LOCALE_T
 		result = strcoll_l(arg1, arg2, locale->info.lt);
-#else
-		/* shouldn't happen */
-		elog(ERROR, "unsupported collprovider: %c", locale->provider);
-#endif
-	}
 	else
 		result = strcoll(arg1, arg2);
 
@@ -2065,11 +2043,9 @@ pg_strxfrm_libc(char *dest, const char *src, size_t destsize,
 	Assert(!locale || locale->provider == COLLPROVIDER_LIBC);
 
 #ifdef TRUST_STRXFRM
-#ifdef HAVE_LOCALE_T
 	if (locale)
 		return strxfrm_l(dest, src, destsize, locale->info.lt);
 	else
-#endif
 		return strxfrm(dest, src, destsize);
 #else
 	/* shouldn't happen */
@@ -2955,7 +2931,6 @@ wchar2char(char *to, const wchar_t *from, size_t tolen, pg_locale_t locale)
 	}
 	else
 	{
-#ifdef HAVE_LOCALE_T
 #ifdef HAVE_WCSTOMBS_L
 		/* Use wcstombs_l for nondefault locales */
 		result = wcstombs_l(to, from, tolen, locale->info.lt);
@@ -2967,11 +2942,6 @@ wchar2char(char *to, const wchar_t *from, size_t tolen, pg_locale_t locale)
 
 		uselocale(save_locale);
 #endif							/* HAVE_WCSTOMBS_L */
-#else							/* !HAVE_LOCALE_T */
-		/* Can't have locale != 0 without HAVE_LOCALE_T */
-		elog(ERROR, "wcstombs_l is not available");
-		result = 0;				/* keep compiler quiet */
-#endif							/* HAVE_LOCALE_T */
 	}
 
 	return result;
@@ -3032,7 +3002,6 @@ char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
 		}
 		else
 		{
-#ifdef HAVE_LOCALE_T
 #ifdef HAVE_MBSTOWCS_L
 			/* Use mbstowcs_l for nondefault locales */
 			result = mbstowcs_l(to, str, tolen, locale->info.lt);
@@ -3044,11 +3013,6 @@ char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
 
 			uselocale(save_locale);
 #endif							/* HAVE_MBSTOWCS_L */
-#else							/* !HAVE_LOCALE_T */
-			/* Can't have locale != 0 without HAVE_LOCALE_T */
-			elog(ERROR, "mbstowcs_l is not available");
-			result = 0;			/* keep compiler quiet */
-#endif							/* HAVE_LOCALE_T */
 		}
 
 		pfree(str);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index ca3a49c552..d03f6e8de8 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -298,9 +298,6 @@
 /* Define to 1 if you have the `zstd' library (-lzstd). */
 #undef HAVE_LIBZSTD
 
-/* Define to 1 if the system has the type `locale_t'. */
-#undef HAVE_LOCALE_T
-
 /* Define to 1 if `long int' works and is 64 bits. */
 #undef HAVE_LONG_INT_64
 
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index b957d5c598..dee85fa3b2 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -458,6 +458,9 @@ extern int	_pglstat64(const char *name, struct stat *buf);
 #define wcstombs_l _wcstombs_l
 #define mbstowcs_l _mbstowcs_l
 
+#define HAVE_WCSTOMBS_L 1
+#define HAVE_MBSTOWCS_L 1
+
 /*
  * Versions of libintl >= 0.18? try to replace setlocale() with a macro
  * to their own versions.  Remove the macro, if it exists, because it
diff --git a/src/include/utils/pg_locale.h b/src/include/utils/pg_locale.h
index e2a7243542..6447bea8e0 100644
--- a/src/include/utils/pg_locale.h
+++ b/src/include/utils/pg_locale.h
@@ -67,9 +67,7 @@ extern void cache_locale_time(void);
 
 
 /*
- * We define our own wrapper around locale_t so we can keep the same
- * function signatures for all builds, while not having to create a
- * fake version of the standard type locale_t in the global namespace.
+ * We use a discriminated union to hold either a locale_t or an ICU collator.
  * pg_locale_t is occasionally checked for truth, so make it a pointer.
  */
 struct pg_locale_struct
@@ -78,9 +76,7 @@ struct pg_locale_struct
 	bool		deterministic;
 	union
 	{
-#ifdef HAVE_LOCALE_T
 		locale_t	lt;
-#endif
 #ifdef USE_ICU
 		struct
 		{
@@ -88,7 +84,6 @@ struct pg_locale_struct
 			UCollator  *ucol;
 		}			icu;
 #endif
-		int			dummy;		/* in case we have neither LOCALE_T nor ICU */
 	}			info;
 };
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index e6d8f9fedc..b6fac0749c 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -296,11 +296,10 @@ sub GenerateFiles
 		HAVE_LIBXSLT => undef,
 		HAVE_LIBZ => $self->{options}->{zlib} ? 1 : undef,
 		HAVE_LIBZSTD => undef,
-		HAVE_LOCALE_T => 1,
 		HAVE_LONG_INT_64 => undef,
 		HAVE_LONG_LONG_INT_64 => 1,
 		HAVE_MBARRIER_H => undef,
-		HAVE_MBSTOWCS_L => 1,
+		HAVE_MBSTOWCS_L => undef, # defined in win32_port.h
 		HAVE_MEMORY_H => 1,
 		HAVE_MEMSET_S => undef,
 		HAVE_MKDTEMP => undef,
@@ -369,7 +368,7 @@ sub GenerateFiles
 		HAVE_UUID_OSSP => undef,
 		HAVE_UUID_H => undef,
 		HAVE_UUID_UUID_H => undef,
-		HAVE_WCSTOMBS_L => 1,
+		HAVE_WCSTOMBS_L => undef, # defined in win32_port.h
 		HAVE_VISIBILITY_ATTRIBUTE => undef,
 		HAVE_X509_GET_SIGNATURE_INFO => undef,
 		HAVE_X86_64_POPCNTQ => undef,
-- 
2.39.2

From a5decf23c6198eb469835b23e9f4ea7778df869c Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Tue, 4 Jul 2023 16:32:35 +1200
Subject: [PATCH v3] All supported systems have locale_t.

locale_t is defined by POSIX.1-2008 and SUSv4, and available on all
targeted systems.  For Windows, win32_port.h redirects to a partial
implementation called _locale_t.  It's time to remove a lot of
compile-time tests for HAVE_LOCALE_T, and a few associated comments and
dead code branches.

Since configure + MinGW builds didn't detect locale_t but now we assume
that all systems have it, further inconsistencies among the 3 Windows build
systems were revealed.  With this commit, we no longer define
HAVE_WCSTOMBS_L and HAVE_MBSTOWCS_L on any Windows build system, but
we have logic to deal with that so that replacements are available where
appropriate.

Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Tristan Partin <tristan@neon.tech>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/CA%2BhUKGLg7_T2GKwZFAkEf0V7vbnur-NfCjZPKZb%3DZfAXSV1ORw%40mail.gmail.com
---
 config/c-library.m4                  | 10 +---
 configure                            |  5 --
 meson.build                          | 22 ++-----
 src/backend/commands/collationcmds.c |  2 +-
 src/backend/regex/regc_pg_locale.c   | 52 +----------------
 src/backend/utils/adt/formatting.c   | 18 ------
 src/backend/utils/adt/like.c         |  2 -
 src/backend/utils/adt/like_support.c |  2 -
 src/backend/utils/adt/pg_locale.c    | 86 +++++++++++-----------------
 src/include/pg_config.h.in           |  3 -
 src/include/utils/pg_locale.h        |  7 +--
 src/tools/msvc/Solution.pm           |  5 +-
 12 files changed, 45 insertions(+), 169 deletions(-)

diff --git a/config/c-library.m4 b/config/c-library.m4
index c1dd804679..aa8223d2ef 100644
--- a/config/c-library.m4
+++ b/config/c-library.m4
@@ -86,9 +86,9 @@ AC_DEFUN([PGAC_STRUCT_SOCKADDR_SA_LEN],
 # PGAC_TYPE_LOCALE_T
 # ------------------
 # Check for the locale_t type and find the right header file.  macOS
-# needs xlocale.h; standard is locale.h, but glibc also has an
-# xlocale.h file that we should not use.
-#
+# needs xlocale.h; standard is locale.h, but glibc <= 2.25 also had an
+# xlocale.h file that we should not use, so we check the standard
+# header first.
 AC_DEFUN([PGAC_TYPE_LOCALE_T],
 [AC_CACHE_CHECK([for locale_t], pgac_cv_type_locale_t,
 [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
@@ -102,10 +102,6 @@ locale_t x;],
 [])],
 [pgac_cv_type_locale_t='yes (in xlocale.h)'],
 [pgac_cv_type_locale_t=no])])])
-if test "$pgac_cv_type_locale_t" != no; then
-  AC_DEFINE(HAVE_LOCALE_T, 1,
-            [Define to 1 if the system has the type `locale_t'.])
-fi
 if test "$pgac_cv_type_locale_t" = 'yes (in xlocale.h)'; then
   AC_DEFINE(LOCALE_T_IN_XLOCALE, 1,
             [Define to 1 if `locale_t' requires <xlocale.h>.])
diff --git a/configure b/configure
index c4463cb17a..842ef855fc 100755
--- a/configure
+++ b/configure
@@ -15120,11 +15120,6 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_type_locale_t" >&5
 $as_echo "$pgac_cv_type_locale_t" >&6; }
-if test "$pgac_cv_type_locale_t" != no; then
-
-$as_echo "#define HAVE_LOCALE_T 1" >>confdefs.h
-
-fi
 if test "$pgac_cv_type_locale_t" = 'yes (in xlocale.h)'; then
 
 $as_echo "#define LOCALE_T_IN_XLOCALE 1" >>confdefs.h
diff --git a/meson.build b/meson.build
index 62942ead09..3d4a85f8c6 100644
--- a/meson.build
+++ b/meson.build
@@ -2283,17 +2283,12 @@ else
   cdata.set('STRERROR_R_INT', false)
 endif
 
-# Check for the locale_t type and find the right header file.  macOS
-# needs xlocale.h; standard is locale.h, but glibc also has an
-# xlocale.h file that we should not use.  MSVC has a replacement
-# defined in src/include/port/win32_port.h.
-if cc.has_type('locale_t', prefix: '#include <locale.h>')
-  cdata.set('HAVE_LOCALE_T', 1)
-elif cc.has_type('locale_t', prefix: '#include <xlocale.h>')
-  cdata.set('HAVE_LOCALE_T', 1)
+# Find the right header file for the locale_t type.  macOS needs xlocale.h;
+# standard is locale.h, but glibc <= 2.25 also had an xlocale.h file that
+# we should not use so we check the standard header first.  MSVC has a
+# replacement defined in src/include/port/win32_port.h.
+if not cc.has_type('locale_t', prefix: '#include <locale.h>') and cc.has_type('locale_t', prefix: '#include <xlocale.h>')
   cdata.set('LOCALE_T_IN_XLOCALE', 1)
-elif cc.get_id() == 'msvc'
-  cdata.set('HAVE_LOCALE_T', 1)
 endif
 
 # Check if the C compiler understands typeof or a variant.  Define
@@ -2489,13 +2484,6 @@ if cc.has_function('syslog', args: test_c_args) and \
 endif
 
 
-# MSVC has replacements defined in src/include/port/win32_port.h.
-if cc.get_id() == 'msvc'
-  cdata.set('HAVE_WCSTOMBS_L', 1)
-  cdata.set('HAVE_MBSTOWCS_L', 1)
-endif
-
-
 # if prerequisites for unnamed posix semas aren't fulfilled, fall back to sysv
 # semaphores
 if sema_kind == 'unnamed_posix' and \
diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index efb8b4d289..cc239b4d14 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -534,7 +534,7 @@ pg_collation_actual_version(PG_FUNCTION_ARGS)
 
 
 /* will we use "locale -a" in pg_import_system_collations? */
-#if defined(HAVE_LOCALE_T) && !defined(WIN32)
+#if !defined(WIN32)
 #define READ_LOCALE_A_OUTPUT
 #endif
 
diff --git a/src/backend/regex/regc_pg_locale.c b/src/backend/regex/regc_pg_locale.c
index 00ce735fdd..31e6300b5d 100644
--- a/src/backend/regex/regc_pg_locale.c
+++ b/src/backend/regex/regc_pg_locale.c
@@ -44,8 +44,7 @@
  * the platform's wchar_t representation matches what we do in pg_wchar
  * conversions.
  *
- * 3. Other collations are only supported on platforms that HAVE_LOCALE_T.
- * Here, we use the locale_t-extended forms of the <wctype.h> and <ctype.h>
+ * 3. Here, we use the locale_t-extended forms of the <wctype.h> and <ctype.h>
  * functions, under exactly the same cases as #2.
  *
  * There is one notable difference between cases 2 and 3: in the "default"
@@ -252,11 +251,6 @@ pg_set_regex_collation(Oid collation)
 	}
 	else
 	{
-		/*
-		 * NB: pg_newlocale_from_collation will fail if not HAVE_LOCALE_T; the
-		 * case of pg_regex_locale != 0 but not HAVE_LOCALE_T does not have to
-		 * be considered below.
-		 */
 		pg_regex_locale = pg_newlocale_from_collation(collation);
 
 		if (!pg_locale_deterministic(pg_regex_locale))
@@ -304,16 +298,12 @@ pg_wc_isdigit(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isdigit((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswdigit_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isdigit_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -340,16 +330,12 @@ pg_wc_isalpha(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalpha((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalpha_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalpha_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -376,16 +362,12 @@ pg_wc_isalnum(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalnum((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalnum_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isalnum_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -421,16 +403,12 @@ pg_wc_isupper(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isupper((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswupper_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isupper_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -457,16 +435,12 @@ pg_wc_islower(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					islower((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswlower_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					islower_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -493,16 +467,12 @@ pg_wc_isgraph(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isgraph((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswgraph_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isgraph_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -529,16 +499,12 @@ pg_wc_isprint(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isprint((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswprint_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isprint_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -565,16 +531,12 @@ pg_wc_ispunct(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					ispunct((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswpunct_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					ispunct_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -601,16 +563,12 @@ pg_wc_isspace(pg_wchar c)
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isspace((unsigned char) c));
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswspace_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			return (c <= (pg_wchar) UCHAR_MAX &&
 					isspace_l((unsigned char) c, pg_regex_locale->info.lt));
-#endif
 			break;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -645,16 +603,12 @@ pg_wc_toupper(pg_wchar c)
 				return toupper((unsigned char) c);
 			return c;
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return towupper_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			if (c <= (pg_wchar) UCHAR_MAX)
 				return toupper_l((unsigned char) c, pg_regex_locale->info.lt);
-#endif
 			return c;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
@@ -689,16 +643,12 @@ pg_wc_tolower(pg_wchar c)
 				return tolower((unsigned char) c);
 			return c;
 		case PG_REGEX_LOCALE_WIDE_L:
-#ifdef HAVE_LOCALE_T
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return towlower_l((wint_t) c, pg_regex_locale->info.lt);
-#endif
 			/* FALL THRU */
 		case PG_REGEX_LOCALE_1BYTE_L:
-#ifdef HAVE_LOCALE_T
 			if (c <= (pg_wchar) UCHAR_MAX)
 				return tolower_l((unsigned char) c, pg_regex_locale->info.lt);
-#endif
 			return c;
 		case PG_REGEX_LOCALE_ICU:
 #ifdef USE_ICU
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index e6246dc44b..e27ea8ef97 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -1613,12 +1613,6 @@ u_strToTitle_default_BI(UChar *dest, int32_t destCapacity,
  * in multibyte character sets.  Note that in either case we are effectively
  * assuming that the database character encoding matches the encoding implied
  * by LC_CTYPE.
- *
- * If the system provides locale_t and associated functions (which are
- * standardized by Open Group's XBD), we can support collations that are
- * neither default nor C.  The code is written to handle both combinations
- * of have-wide-characters and have-locale_t, though it's rather unlikely
- * a platform would have the latter without the former.
  */
 
 /*
@@ -1696,11 +1690,9 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						workspace[curr_char] = towlower_l(workspace[curr_char], mylocale->info.lt);
 					else
-#endif
 						workspace[curr_char] = towlower(workspace[curr_char]);
 				}
 
@@ -1729,11 +1721,9 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						*p = tolower_l((unsigned char) *p, mylocale->info.lt);
 					else
-#endif
 						*p = pg_tolower((unsigned char) *p);
 				}
 			}
@@ -1818,11 +1808,9 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						workspace[curr_char] = towupper_l(workspace[curr_char], mylocale->info.lt);
 					else
-#endif
 						workspace[curr_char] = towupper(workspace[curr_char]);
 				}
 
@@ -1851,11 +1839,9 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 						*p = toupper_l((unsigned char) *p, mylocale->info.lt);
 					else
-#endif
 						*p = pg_toupper((unsigned char) *p);
 				}
 			}
@@ -1941,7 +1927,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 
 				for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 					{
 						if (wasalnum)
@@ -1951,7 +1936,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 						wasalnum = iswalnum_l(workspace[curr_char], mylocale->info.lt);
 					}
 					else
-#endif
 					{
 						if (wasalnum)
 							workspace[curr_char] = towlower(workspace[curr_char]);
@@ -1986,7 +1970,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 				 */
 				for (p = result; *p; p++)
 				{
-#ifdef HAVE_LOCALE_T
 					if (mylocale)
 					{
 						if (wasalnum)
@@ -1996,7 +1979,6 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 						wasalnum = isalnum_l((unsigned char) *p, mylocale->info.lt);
 					}
 					else
-#endif
 					{
 						if (wasalnum)
 							*p = pg_tolower((unsigned char) *p);
diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index 33a2f46aab..62902caefa 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -95,10 +95,8 @@ SB_lower_char(unsigned char c, pg_locale_t locale, bool locale_is_c)
 {
 	if (locale_is_c)
 		return pg_ascii_tolower(c);
-#ifdef HAVE_LOCALE_T
 	else if (locale)
 		return tolower_l(c, locale->info.lt);
-#endif
 	else
 		return pg_tolower(c);
 }
diff --git a/src/backend/utils/adt/like_support.c b/src/backend/utils/adt/like_support.c
index 9b603d42f3..34e1b709ae 100644
--- a/src/backend/utils/adt/like_support.c
+++ b/src/backend/utils/adt/like_support.c
@@ -1509,10 +1509,8 @@ pattern_char_isalpha(char c, bool is_multibyte,
 	else if (locale && locale->provider == COLLPROVIDER_ICU)
 		return IS_HIGHBIT_SET(c) ||
 			(c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
-#ifdef HAVE_LOCALE_T
 	else if (locale && locale->provider == COLLPROVIDER_LIBC)
 		return isalpha_l((unsigned char) c, locale->info.lt);
-#endif
 	else
 		return isalpha((unsigned char) c);
 }
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index c8b36f3af2..0eb764e897 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -154,6 +154,38 @@ 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.
+ */
+#ifndef HAVE_MBSTOWCS_L
+static size_t
+mbstowcs_l(wchar_t *dest, const char *src, size_t n, locale_t loc)
+{
+	size_t		result;
+	locale_t	save_locale = uselocale(loc);
+
+	result = mbstowcs(dest, src, n);
+	uselocale(save_locale);
+	return result;
+}
+#endif
+#ifndef HAVE_WCSTOMBS_L
+static size_t
+wcstombs_l(char *dest, const wchar_t *src, size_t n, locale_t loc)
+{
+	size_t		result;
+	locale_t	save_locale = uselocale(loc);
+
+	result = wcstombs(dest, src, n);
+	uselocale(save_locale);
+	return result;
+}
+#endif
+#endif
+
 /*
  * pg_perm_setlocale
  *
@@ -1420,7 +1452,6 @@ make_icu_collator(const char *iculocstr,
 
 
 /* simple subroutine for reporting errors from newlocale() */
-#ifdef HAVE_LOCALE_T
 static void
 report_newlocale_failure(const char *localename)
 {
@@ -1449,7 +1480,6 @@ report_newlocale_failure(const char *localename)
 			  errdetail("The operating system could not find any locale data for the locale name \"%s\".",
 						localename) : 0)));
 }
-#endif							/* HAVE_LOCALE_T */
 
 bool
 pg_locale_deterministic(pg_locale_t locale)
@@ -1466,10 +1496,6 @@ pg_locale_deterministic(pg_locale_t locale)
  * lifetime of the backend.  Thus, do not free the result with freelocale().
  *
  * As a special optimization, the default/database collation returns 0.
- * Callers should then revert to the non-locale_t-enabled code path.
- * Also, callers should avoid calling this before going down a C/POSIX
- * fastpath, because such a fastpath should work even on platforms without
- * locale_t support in the C library.
  *
  * For simplicity, we always generate COLLATE + CTYPE even though we
  * might only need one of them.  Since this is called only once per session,
@@ -1515,7 +1541,6 @@ pg_newlocale_from_collation(Oid collid)
 
 		if (collform->collprovider == COLLPROVIDER_LIBC)
 		{
-#ifdef HAVE_LOCALE_T
 			const char *collcollate;
 			const char *collctype pg_attribute_unused();
 			locale_t	loc;
@@ -1566,12 +1591,6 @@ pg_newlocale_from_collation(Oid collid)
 			}
 
 			result.info.lt = loc;
-#else							/* not HAVE_LOCALE_T */
-			/* platform that doesn't support locale_t */
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("collation provider LIBC is not supported on this platform")));
-#endif							/* not HAVE_LOCALE_T */
 		}
 		else if (collform->collprovider == COLLPROVIDER_ICU)
 		{
@@ -1788,11 +1807,9 @@ pg_strncoll_libc_win32_utf8(const char *arg1, size_t len1, const char *arg2,
 	((LPWSTR) a2p)[r] = 0;
 
 	errno = 0;
-#ifdef HAVE_LOCALE_T
 	if (locale)
 		result = wcscoll_l((LPWSTR) a1p, (LPWSTR) a2p, locale->info.lt);
 	else
-#endif
 		result = wcscoll((LPWSTR) a1p, (LPWSTR) a2p);
 	if (result == 2147483647)	/* _NLSCMPERROR; missing from mingw headers */
 		ereport(ERROR,
@@ -1831,14 +1848,7 @@ pg_strcoll_libc(const char *arg1, const char *arg2, pg_locale_t locale)
 	else
 #endif							/* WIN32 */
 	if (locale)
-	{
-#ifdef HAVE_LOCALE_T
 		result = strcoll_l(arg1, arg2, locale->info.lt);
-#else
-		/* shouldn't happen */
-		elog(ERROR, "unsupported collprovider: %c", locale->provider);
-#endif
-	}
 	else
 		result = strcoll(arg1, arg2);
 
@@ -2065,11 +2075,9 @@ pg_strxfrm_libc(char *dest, const char *src, size_t destsize,
 	Assert(!locale || locale->provider == COLLPROVIDER_LIBC);
 
 #ifdef TRUST_STRXFRM
-#ifdef HAVE_LOCALE_T
 	if (locale)
 		return strxfrm_l(dest, src, destsize, locale->info.lt);
 	else
-#endif
 		return strxfrm(dest, src, destsize);
 #else
 	/* shouldn't happen */
@@ -2955,23 +2963,8 @@ wchar2char(char *to, const wchar_t *from, size_t tolen, pg_locale_t locale)
 	}
 	else
 	{
-#ifdef HAVE_LOCALE_T
-#ifdef HAVE_WCSTOMBS_L
 		/* Use wcstombs_l for nondefault locales */
 		result = wcstombs_l(to, from, tolen, locale->info.lt);
-#else							/* !HAVE_WCSTOMBS_L */
-		/* We have to temporarily set the locale as current ... ugh */
-		locale_t	save_locale = uselocale(locale->info.lt);
-
-		result = wcstombs(to, from, tolen);
-
-		uselocale(save_locale);
-#endif							/* HAVE_WCSTOMBS_L */
-#else							/* !HAVE_LOCALE_T */
-		/* Can't have locale != 0 without HAVE_LOCALE_T */
-		elog(ERROR, "wcstombs_l is not available");
-		result = 0;				/* keep compiler quiet */
-#endif							/* HAVE_LOCALE_T */
 	}
 
 	return result;
@@ -3032,23 +3025,8 @@ char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
 		}
 		else
 		{
-#ifdef HAVE_LOCALE_T
-#ifdef HAVE_MBSTOWCS_L
 			/* Use mbstowcs_l for nondefault locales */
 			result = mbstowcs_l(to, str, tolen, locale->info.lt);
-#else							/* !HAVE_MBSTOWCS_L */
-			/* We have to temporarily set the locale as current ... ugh */
-			locale_t	save_locale = uselocale(locale->info.lt);
-
-			result = mbstowcs(to, str, tolen);
-
-			uselocale(save_locale);
-#endif							/* HAVE_MBSTOWCS_L */
-#else							/* !HAVE_LOCALE_T */
-			/* Can't have locale != 0 without HAVE_LOCALE_T */
-			elog(ERROR, "mbstowcs_l is not available");
-			result = 0;			/* keep compiler quiet */
-#endif							/* HAVE_LOCALE_T */
 		}
 
 		pfree(str);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index ca3a49c552..d03f6e8de8 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -298,9 +298,6 @@
 /* Define to 1 if you have the `zstd' library (-lzstd). */
 #undef HAVE_LIBZSTD
 
-/* Define to 1 if the system has the type `locale_t'. */
-#undef HAVE_LOCALE_T
-
 /* Define to 1 if `long int' works and is 64 bits. */
 #undef HAVE_LONG_INT_64
 
diff --git a/src/include/utils/pg_locale.h b/src/include/utils/pg_locale.h
index e2a7243542..6447bea8e0 100644
--- a/src/include/utils/pg_locale.h
+++ b/src/include/utils/pg_locale.h
@@ -67,9 +67,7 @@ extern void cache_locale_time(void);
 
 
 /*
- * We define our own wrapper around locale_t so we can keep the same
- * function signatures for all builds, while not having to create a
- * fake version of the standard type locale_t in the global namespace.
+ * We use a discriminated union to hold either a locale_t or an ICU collator.
  * pg_locale_t is occasionally checked for truth, so make it a pointer.
  */
 struct pg_locale_struct
@@ -78,9 +76,7 @@ struct pg_locale_struct
 	bool		deterministic;
 	union
 	{
-#ifdef HAVE_LOCALE_T
 		locale_t	lt;
-#endif
 #ifdef USE_ICU
 		struct
 		{
@@ -88,7 +84,6 @@ struct pg_locale_struct
 			UCollator  *ucol;
 		}			icu;
 #endif
-		int			dummy;		/* in case we have neither LOCALE_T nor ICU */
 	}			info;
 };
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 133acc09f2..f09b3826ff 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -296,11 +296,10 @@ sub GenerateFiles
 		HAVE_LIBXSLT => undef,
 		HAVE_LIBZ => $self->{options}->{zlib} ? 1 : undef,
 		HAVE_LIBZSTD => undef,
-		HAVE_LOCALE_T => 1,
 		HAVE_LONG_INT_64 => undef,
 		HAVE_LONG_LONG_INT_64 => 1,
 		HAVE_MBARRIER_H => undef,
-		HAVE_MBSTOWCS_L => 1,
+		HAVE_MBSTOWCS_L => undef,
 		HAVE_MEMORY_H => 1,
 		HAVE_MEMSET_S => undef,
 		HAVE_MKDTEMP => undef,
@@ -369,7 +368,7 @@ sub GenerateFiles
 		HAVE_UUID_OSSP => undef,
 		HAVE_UUID_H => undef,
 		HAVE_UUID_UUID_H => undef,
-		HAVE_WCSTOMBS_L => 1,
+		HAVE_WCSTOMBS_L => undef,
 		HAVE_VISIBILITY_ATTRIBUTE => undef,
 		HAVE_X509_GET_SIGNATURE_INFO => undef,
 		HAVE_X86_64_POPCNTQ => undef,
-- 
2.39.2

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