From 8f80c62aa2a3307d0d6248fbb2116851edcdcce4 Mon Sep 17 00:00:00 2001
From: Frank Tang <ftang@chromium.org>
Date: Wed, 24 Jan 2024 16:06:17 -0800
Subject: [PATCH] ICU-22638 Fix cast overflow issue

---
 icu4c/source/i18n/plurrule.cpp          | 4 +++-
 icu4c/source/test/intltest/plurults.cpp | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/icu4c/source/i18n/plurrule.cpp b/icu4c/source/i18n/plurrule.cpp
index 1a9bdf47125..cd460bd0b10 100644
--- a/icu4c/source/i18n/plurrule.cpp
+++ b/icu4c/source/i18n/plurrule.cpp
@@ -1778,7 +1778,9 @@ void FixedDecimal::init(double n, int32_t v, int64_t f, int32_t e, int32_t c) {
     if (exponent == 0) {
         exponent = c;
     }
-    if (_isNaN || _isInfinite) {
+    if (_isNaN || _isInfinite ||
+        source > static_cast<double>(U_INT64_MAX) ||
+        source < static_cast<double>(U_INT64_MIN)) {
         v = 0;
         f = 0;
         intValue = 0;
diff --git a/icu4c/source/test/intltest/plurults.cpp b/icu4c/source/test/intltest/plurults.cpp
index fb95ef43dc7..bdeac269e8c 100644
--- a/icu4c/source/test/intltest/plurults.cpp
+++ b/icu4c/source/test/intltest/plurults.cpp
@@ -243,8 +243,8 @@ void PluralRulesTest::testAPI(/*char *par*/)
         dataerrln("ERROR: Could not create PluralRules for testing fractions - exiting");
         return;
     }
-    double fData[] =     {-101, -100, -1,     -0.0,  0,     0.1,  1,     1.999,  2.0,   100,   100.001 };
-    bool isKeywordA[] = {true, false, false, false, false, true, false,  true,   false, false, true };
+    double fData[] =     {-101, -100, -1,     -0.0,  0,     0.1,  1,     1.999,  2.0,   100,   100.001, 1.39e188 };
+    bool isKeywordA[] = {true, false, false, false, false, true, false,  true,   false, false, true, true };
     for (int32_t i=0; i<UPRV_LENGTHOF(fData); i++) {
         if ((newRules->select(fData[i])== KEYWORD_A) != isKeywordA[i]) {
              errln("File %s, Line %d, ERROR: plural rules for decimal fractions test failed!\n"