From 1dccc100852673c7d3b41542d2130b3871b5c6cf Mon Sep 17 00:00:00 2001
From: Fredrik Roubert <roubert@google.com>
Date: Thu, 3 Oct 2024 18:03:13 +0200
Subject: [PATCH] ICU-22901 Move calls to uloc_getDefault() out of
 ulocimp_getSubtags().

---
 icu4c/source/common/locdispnames.cpp |  4 ++++
 icu4c/source/common/loclikely.cpp    |  6 ++++--
 icu4c/source/common/uloc.cpp         | 20 ++++++++++++++++----
 icu4c/source/common/uscript.cpp      |  3 +++
 4 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/icu4c/source/common/locdispnames.cpp b/icu4c/source/common/locdispnames.cpp
index ddf7687a2bf..2a3c81f9096 100644
--- a/icu4c/source/common/locdispnames.cpp
+++ b/icu4c/source/common/locdispnames.cpp
@@ -377,6 +377,10 @@ _getDisplayNameForComponent(const char *locale,
         return 0;
     }
 
+    if (locale == nullptr) {
+        locale = uloc_getDefault();
+    }
+
     localStatus = U_ZERO_ERROR;
     icu::CharString localeBuffer = (*getter)(locale, localStatus);
     if (U_FAILURE(localStatus)) {
diff --git a/icu4c/source/common/loclikely.cpp b/icu4c/source/common/loclikely.cpp
index ccbcbfa7a5d..429c44887bf 100644
--- a/icu4c/source/common/loclikely.cpp
+++ b/icu4c/source/common/loclikely.cpp
@@ -349,7 +349,9 @@ uloc_isRightToLeft(const char *locale) {
     UErrorCode errorCode = U_ZERO_ERROR;
     icu::CharString lang;
     icu::CharString script;
-    ulocimp_getSubtags(locale, &lang, &script, nullptr, nullptr, nullptr, errorCode);
+    ulocimp_getSubtags(
+        locale == nullptr ? uloc_getDefault() : locale,
+        &lang, &script, nullptr, nullptr, nullptr, errorCode);
     if (U_FAILURE(errorCode) || script.isEmpty()) {
         // Fastpath: We know the likely scripts and their writing direction
         // for some common languages.
@@ -430,7 +432,7 @@ ulocimp_getRegionForSupplementalData(const char *localeID, bool inferRegion,
     icu::CharString rgBuf = GetRegionFromKey(localeID, "rg", status);
     if (U_SUCCESS(status) && rgBuf.isEmpty()) {
         // No valid rg keyword value, try for unicode_region_subtag
-        rgBuf = ulocimp_getRegion(localeID, status);
+        rgBuf = ulocimp_getRegion(localeID == nullptr ? uloc_getDefault() : localeID, status);
         if (U_SUCCESS(status) && rgBuf.isEmpty() && inferRegion) {
             // Second check for sd keyword value
             rgBuf = GetRegionFromKey(localeID, "sd", status);
diff --git a/icu4c/source/common/uloc.cpp b/icu4c/source/common/uloc.cpp
index 51887c97c3e..9668d0bef0c 100644
--- a/icu4c/source/common/uloc.cpp
+++ b/icu4c/source/common/uloc.cpp
@@ -1541,10 +1541,6 @@ ulocimp_getSubtags(
 
     bool hasRegion = false;
 
-    if (localeID == nullptr) {
-        localeID = uloc_getDefault();
-    }
-
     _getLanguage(localeID, language, &localeID, status);
     if (U_FAILURE(status)) { return; }
     U_ASSERT(localeID != nullptr);
@@ -1989,6 +1985,10 @@ uloc_getLanguage(const char*    localeID,
          int32_t languageCapacity,
          UErrorCode* err)
 {
+    if (localeID == nullptr) {
+        localeID = uloc_getDefault();
+    }
+
     /* uloc_getLanguage will return a 2 character iso-639 code if one exists. *CWB*/
     return ByteSinkUtil::viaByteSinkToTerminatedChars(
         language, languageCapacity,
@@ -2011,6 +2011,10 @@ uloc_getScript(const char*    localeID,
          int32_t scriptCapacity,
          UErrorCode* err)
 {
+    if (localeID == nullptr) {
+        localeID = uloc_getDefault();
+    }
+
     return ByteSinkUtil::viaByteSinkToTerminatedChars(
         script, scriptCapacity,
         [&](ByteSink& sink, UErrorCode& status) {
@@ -2032,6 +2036,10 @@ uloc_getCountry(const char* localeID,
             int32_t countryCapacity,
             UErrorCode* err)
 {
+    if (localeID == nullptr) {
+        localeID = uloc_getDefault();
+    }
+
     return ByteSinkUtil::viaByteSinkToTerminatedChars(
         country, countryCapacity,
         [&](ByteSink& sink, UErrorCode& status) {
@@ -2053,6 +2061,10 @@ uloc_getVariant(const char* localeID,
                 int32_t variantCapacity,
                 UErrorCode* err)
 {
+    if (localeID == nullptr) {
+        localeID = uloc_getDefault();
+    }
+
     return ByteSinkUtil::viaByteSinkToTerminatedChars(
         variant, variantCapacity,
         [&](ByteSink& sink, UErrorCode& status) {
diff --git a/icu4c/source/common/uscript.cpp b/icu4c/source/common/uscript.cpp
index c48a28fd143..ce40d354958 100644
--- a/icu4c/source/common/uscript.cpp
+++ b/icu4c/source/common/uscript.cpp
@@ -59,6 +59,9 @@ getCodesFromLocale(const char *locale,
     if (U_FAILURE(*err)) { return 0; }
     icu::CharString lang;
     icu::CharString script;
+    if (locale == nullptr) {
+        locale = uloc_getDefault();
+    }
     ulocimp_getSubtags(locale, &lang, &script, nullptr, nullptr, nullptr, *err);
     if (U_FAILURE(*err)) { return 0; }
     // Multi-script languages, equivalent to the LocaleScript data