From 9bce52f003496527b2e37e31ae08521cd35212ac Mon Sep 17 00:00:00 2001
From: Fredrik Roubert <roubert@google.com>
Date: Tue, 26 Sep 2023 01:08:04 +0200
Subject: [PATCH] ICU-21289 Switch to using CharString for calling
 uloc_toLanguageTag().

---
 icu4c/source/common/locmap.cpp |  7 +++++--
 icu4c/source/i18n/windtfmt.cpp | 10 ++++++++--
 icu4c/source/i18n/winnmfmt.cpp | 10 ++++++++--
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/icu4c/source/common/locmap.cpp b/icu4c/source/common/locmap.cpp
index 1d5e1f2a75c..e41cfd1027d 100644
--- a/icu4c/source/common/locmap.cpp
+++ b/icu4c/source/common/locmap.cpp
@@ -1200,9 +1200,12 @@ uprv_convertToLCIDPlatform(const char* localeID, UErrorCode* status)
         }
     }
 
-    char asciiBCP47Tag[LOCALE_NAME_MAX_LENGTH] = {};
     // this will change it from de_DE@collation=phonebook to de-DE-u-co-phonebk form
-    (void)uloc_toLanguageTag(mylocaleID, asciiBCP47Tag, UPRV_LENGTHOF(asciiBCP47Tag), false, status);
+    icu::CharString asciiBCP47Tag;
+    {
+        icu::CharStringByteSink sink(&asciiBCP47Tag);
+        ulocimp_toLanguageTag(mylocaleID, sink, false, status);
+    }
 
     if (U_SUCCESS(*status))
     {
diff --git a/icu4c/source/i18n/windtfmt.cpp b/icu4c/source/i18n/windtfmt.cpp
index 2118f92dceb..6d705b299d7 100644
--- a/icu4c/source/i18n/windtfmt.cpp
+++ b/icu4c/source/i18n/windtfmt.cpp
@@ -30,7 +30,10 @@
 #include "unicode/timezone.h"
 #include "unicode/utmscale.h"
 
+#include "bytesinkutil.h"
+#include "charstr.h"
 #include "cmemory.h"
+#include "ulocimp.h"
 #include "uresimp.h"
 #include "windtfmt.h"
 #include "wintzimpl.h"
@@ -99,10 +102,13 @@ UnicodeString* Win32DateFormat::getTimeDateFormat(const Calendar *cal, const Loc
 static UErrorCode GetEquivalentWindowsLocaleName(const Locale& locale, UnicodeString** buffer)
 {
     UErrorCode status = U_ZERO_ERROR;
-    char asciiBCP47Tag[LOCALE_NAME_MAX_LENGTH] = {};
 
     // Convert from names like "en_CA" and "de_DE@collation=phonebook" to "en-CA" and "de-DE-u-co-phonebk".
-    (void)uloc_toLanguageTag(locale.getName(), asciiBCP47Tag, UPRV_LENGTHOF(asciiBCP47Tag), false, &status);
+    CharString asciiBCP47Tag;
+    {
+        CharStringByteSink sink(&asciiBCP47Tag);
+        ulocimp_toLanguageTag(locale.getName(), sink, false, &status);
+    }
 
     if (U_SUCCESS(status))
     {
diff --git a/icu4c/source/i18n/winnmfmt.cpp b/icu4c/source/i18n/winnmfmt.cpp
index 6efa9a63d86..bf0bd20095c 100644
--- a/icu4c/source/i18n/winnmfmt.cpp
+++ b/icu4c/source/i18n/winnmfmt.cpp
@@ -24,8 +24,11 @@
 #include "unicode/locid.h"
 #include "unicode/ustring.h"
 
+#include "bytesinkutil.h"
+#include "charstr.h"
 #include "cmemory.h"
 #include "uassert.h"
+#include "ulocimp.h"
 #include "locmap.h"
 
 #ifndef WIN32_LEAN_AND_MEAN
@@ -144,10 +147,13 @@ static void freeCurrencyFormat(CURRENCYFMTW *fmt)
 static UErrorCode GetEquivalentWindowsLocaleName(const Locale& locale, UnicodeString** buffer)
 {
     UErrorCode status = U_ZERO_ERROR;
-    char asciiBCP47Tag[LOCALE_NAME_MAX_LENGTH] = {};
 
     // Convert from names like "en_CA" and "de_DE@collation=phonebook" to "en-CA" and "de-DE-u-co-phonebk".
-    (void) uloc_toLanguageTag(locale.getName(), asciiBCP47Tag, UPRV_LENGTHOF(asciiBCP47Tag), false, &status);
+    CharString asciiBCP47Tag;
+    {
+        CharStringByteSink sink(&asciiBCP47Tag);
+        ulocimp_toLanguageTag(locale.getName(), sink, false, &status);
+    }
 
     if (U_SUCCESS(status))
     {