From fd5a346b3de386b6e72ee72d17730f6cf116e9f5 Mon Sep 17 00:00:00 2001
From: Andy Heninger <andy.heninger@gmail.com>
Date: Fri, 29 Oct 2021 17:17:41 -0700
Subject: [PATCH] ICU-21778 UnicodeString::clone error handling fix

Change UnicodeString::clone() to return a nullptr if the underlying copy
constructor produces a bogus string. This can happen if the copy constructor
encounters a memory allocation failure in allocating the copy's internal string
buffer, or if the string being copied was already bogus.

The change is consistent with other ICU clone functions, which are generally
defined to return nullptr in case of errors.
---
 icu4c/source/common/unistr.cpp          |  3 ++-
 icu4c/source/test/intltest/ustrtest.cpp | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/icu4c/source/common/unistr.cpp b/icu4c/source/common/unistr.cpp
index 077b4d6ef20..918693898d1 100644
--- a/icu4c/source/common/unistr.cpp
+++ b/icu4c/source/common/unistr.cpp
@@ -334,7 +334,8 @@ Replaceable::clone() const {
 // UnicodeString overrides clone() with a real implementation
 UnicodeString *
 UnicodeString::clone() const {
-  return new UnicodeString(*this);
+  LocalPointer<UnicodeString> clonedString(new UnicodeString(*this));
+  return clonedString.isValid() && !clonedString->isBogus() ? clonedString.orphan() : nullptr;
 }
 
 //========================================
diff --git a/icu4c/source/test/intltest/ustrtest.cpp b/icu4c/source/test/intltest/ustrtest.cpp
index cd9751d761b..11bbb6e27af 100644
--- a/icu4c/source/test/intltest/ustrtest.cpp
+++ b/icu4c/source/test/intltest/ustrtest.cpp
@@ -1653,6 +1653,16 @@ UnicodeStringTest::TestBogus() {
     if(test1>=test2 || !(test2>test1) || test1.compare(test2)>=0 || !(test2.compare(test1)>0)) {
         errln("bogus<empty failed");
     }
+
+    // test that copy constructor of bogus is bogus & clone of bogus is nullptr
+    {
+        test3.setToBogus();
+        UnicodeString test3Copy(test3);
+        UnicodeString *test3Clone = test3.clone();
+        assertTrue(WHERE, test3.isBogus());
+        assertTrue(WHERE, test3Copy.isBogus());
+        assertTrue(WHERE, test3Clone == nullptr);
+    }
 }
 
 // StringEnumeration ------------------------------------------------------- ***