1 files changed, 22 insertions, 11 deletions
diff --git a/deps/icu-small/source/i18n/currunit.cpp b/deps/icu-small/source/i18n/currunit.cpp
index 83429c0169..6d8d1cd6c6 100644
--- a/deps/icu-small/source/i18n/currunit.cpp
+++ b/deps/icu-small/source/i18n/currunit.cpp
@@ -17,21 +17,32 @@
 #include "unicode/currunit.h"
 #include "unicode/ustring.h"
 #include "cstring.h"
+#include "uinvchar.h"
+
+static constexpr char16_t kDefaultCurrency[] = u"XXX";
 
 U_NAMESPACE_BEGIN
 
 CurrencyUnit::CurrencyUnit(ConstChar16Ptr _isoCode, UErrorCode& ec) {
-    *isoCode = 0;
-    if (U_SUCCESS(ec)) {
-        if (_isoCode != nullptr && u_strlen(_isoCode)==3) {
-            u_strcpy(isoCode, _isoCode);
-            char simpleIsoCode[4];
-            u_UCharsToChars(isoCode, simpleIsoCode, 4);
-            initCurrency(simpleIsoCode);
-        } else {
-            ec = U_ILLEGAL_ARGUMENT_ERROR;
-        }
+    // The constructor always leaves the CurrencyUnit in a valid state (with a 3-character currency code).
+    // Note: in ICU4J Currency.getInstance(), we check string length for 3, but in ICU4C we allow a
+    // non-NUL-terminated string to be passed as an argument, so it is not possible to check length.
+    const char16_t* isoCodeToUse;
+    if (U_FAILURE(ec) || _isoCode == nullptr) {
+        isoCodeToUse = kDefaultCurrency;
+    } else if (!uprv_isInvariantUString(_isoCode, 3)) {
+        // TODO: Perform a more strict ASCII check like in ICU4J isAlpha3Code?
+        isoCodeToUse = kDefaultCurrency;
+        ec = U_INVARIANT_CONVERSION_ERROR;
+    } else {
+        isoCodeToUse = _isoCode;
     }
+    // TODO: Perform uppercasing here like in ICU4J Currency.getInstance()?
+    uprv_memcpy(isoCode, isoCodeToUse, sizeof(UChar) * 3);
+    isoCode[3] = 0;
+    char simpleIsoCode[4];
+    u_UCharsToChars(isoCode, simpleIsoCode, 4);
+    initCurrency(simpleIsoCode);
 }
 
 CurrencyUnit::CurrencyUnit(const CurrencyUnit& other) : MeasureUnit(other) {
@@ -52,7 +63,7 @@ CurrencyUnit::CurrencyUnit(const MeasureUnit& other, UErrorCode& ec) : MeasureUn
 }
 
 CurrencyUnit::CurrencyUnit() : MeasureUnit() {
-    u_strcpy(isoCode, u"XXX");
+    u_strcpy(isoCode, kDefaultCurrency);
     char simpleIsoCode[4];
     u_UCharsToChars(isoCode, simpleIsoCode, 4);
     initCurrency(simpleIsoCode);