From 07137b64e454dfda7ab0c46eaaa55d6bfc29e399 Mon Sep 17 00:00:00 2001
From: Frank Tang <ftang@chromium.org>
Date: Thu, 28 Sep 2023 00:26:31 -0700
Subject: [PATCH] ICU-22521 Return U_INTERNAL_PROGRAM_ERROR instead of % 0

When the gap is 0, return status as U_INTERNAL_PROGRAM_ERROR
and avoid the operation of "% gap"
---
 icu4c/source/i18n/calendar.cpp         |  8 ++++++++
 icu4c/source/test/intltest/caltest.cpp | 12 ++++++++++++
 icu4c/source/test/intltest/caltest.h   |  1 +
 3 files changed, 21 insertions(+)

diff --git a/icu4c/source/i18n/calendar.cpp b/icu4c/source/i18n/calendar.cpp
index 742891eb928..a296599ef5d 100644
--- a/icu4c/source/i18n/calendar.cpp
+++ b/icu4c/source/i18n/calendar.cpp
@@ -1927,6 +1927,10 @@ void Calendar::roll(UCalendarDateFields field, int32_t amount, UErrorCode& statu
 
             // Now roll between start and (limit - 1).
             int32_t gap = limit - start;
+            if (gap == 0) {
+                status =  U_INTERNAL_PROGRAM_ERROR;
+                return;
+            }
             int32_t day_of_month = (internalGet(UCAL_DAY_OF_MONTH) + amount*7 -
                 start) % gap;
             if (day_of_month < 0) day_of_month += gap;
@@ -1985,6 +1989,10 @@ void Calendar::roll(UCalendarDateFields field, int32_t amount, UErrorCode& statu
 
             // Now roll between start and (limit - 1).
             int32_t gap = limit - start;
+            if (gap == 0) {
+                status =  U_INTERNAL_PROGRAM_ERROR;
+                return;
+            }
             int32_t day_of_year = (internalGet(UCAL_DAY_OF_YEAR) + amount*7 -
                 start) % gap;
             if (day_of_year < 0) day_of_year += gap;
diff --git a/icu4c/source/test/intltest/caltest.cpp b/icu4c/source/test/intltest/caltest.cpp
index 86ed3d2e659..73476293f7d 100644
--- a/icu4c/source/test/intltest/caltest.cpp
+++ b/icu4c/source/test/intltest/caltest.cpp
@@ -188,6 +188,7 @@ void CalendarTest::runIndexedTest( int32_t index, UBool exec, const char* &name,
 
     TESTCASE_AUTO(TestFWWithISO8601);
     TESTCASE_AUTO(TestDangiOverflowIsLeapMonthBetween22507);
+    TESTCASE_AUTO(TestRollWeekOfYear);
 
     TESTCASE_AUTO_END;
 }
@@ -5540,6 +5541,17 @@ void CalendarTest::TestFWWithISO8601() {
         assertEquals(msg.c_str(), i, cal->getFirstDayOfWeek());
     }
 }
+void CalendarTest::TestRollWeekOfYear() {
+    UErrorCode status = U_ZERO_ERROR;
+    Locale l("zh_TW@calendar=chinese");
+    LocalPointer<Calendar> cal(Calendar::createInstance(l, status), status);
+    cal->set(UCAL_EXTENDED_YEAR, -1107626);
+    cal->set(UCAL_MONTH, UCAL_JANUARY);
+    cal->set(UCAL_DATE, 1);
+    cal->roll(UCAL_WEEK_OF_YEAR, 0x7fffff, status);
+    U_ASSERT(U_SUCCESS(status));
+    cal->roll(UCAL_WEEK_OF_YEAR, 1, status);
+}
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
 //eof
diff --git a/icu4c/source/test/intltest/caltest.h b/icu4c/source/test/intltest/caltest.h
index 74261d56630..23ef779408f 100644
--- a/icu4c/source/test/intltest/caltest.h
+++ b/icu4c/source/test/intltest/caltest.h
@@ -332,6 +332,7 @@ public: // package
     void TestDangiOverflowIsLeapMonthBetween22507();
 
     void TestFWWithISO8601();
+    void TestRollWeekOfYear();
 
     void RunChineseCalendarInTemporalLeapYearTest(Calendar* cal);
     void RunIslamicCalendarInTemporalLeapYearTest(Calendar* cal);