ICU-22520 Use operator* instead of calling std::optional::value().

There's a subtle difference between these two ways of accessing the
value of an optional and that is that the value() method can throw an
exception if there isn't any value, but operator* won't do that (it's
just undefined behavior if there isn't any value).

ICU4C code never tries to access any optional value without first
checking that it exists, but the ability of the value() method to throw
an exception in case there wasn't any such check first is the reason why
std::exception symbols previously could show up in debug builds.

This reverts the changes that were made to dependencies.txt by
commit dc70b5a.

icu4c/source/common/localematcher.cpp

@@ -610,7 +610,7 @@ const Locale *LocaleMatcher::getBestMatch(const Locale &desiredLocale, UErrorCod
     std::optional<int32_t> suppIndex = getBestSuppIndex(
         getMaximalLsrOrUnd(likelySubtags, desiredLocale, errorCode),
         nullptr, errorCode);
-    return U_SUCCESS(errorCode) && suppIndex.has_value() ? supportedLocales[suppIndex.value()]
+    return U_SUCCESS(errorCode) && suppIndex.has_value() ? supportedLocales[*suppIndex]
                                                          : defaultLocale;
 }
 
@@ -622,7 +622,7 @@ const Locale *LocaleMatcher::getBestMatch(Locale::Iterator &desiredLocales,
     }
     LocaleLsrIterator lsrIter(likelySubtags, desiredLocales, ULOCMATCH_TEMPORARY_LOCALES);
     std::optional<int32_t> suppIndex = getBestSuppIndex(lsrIter.next(errorCode), &lsrIter, errorCode);
-    return U_SUCCESS(errorCode) && suppIndex.has_value() ? supportedLocales[suppIndex.value()]
+    return U_SUCCESS(errorCode) && suppIndex.has_value() ? supportedLocales[*suppIndex]
                                                          : defaultLocale;
 }
 
@@ -645,7 +645,7 @@ LocaleMatcher::Result LocaleMatcher::getBestMatchResult(
     if (U_FAILURE(errorCode) || !suppIndex.has_value()) {
         return Result(nullptr, defaultLocale, -1, -1, false);
     } else {
-        return Result(&desiredLocale, supportedLocales[suppIndex.value()], 0, suppIndex.value(), false);
+        return Result(&desiredLocale, supportedLocales[*suppIndex], 0, *suppIndex, false);
     }
 }
 
@@ -659,8 +659,8 @@ LocaleMatcher::Result LocaleMatcher::getBestMatchResult(
     if (U_FAILURE(errorCode) || !suppIndex.has_value()) {
         return Result(nullptr, defaultLocale, -1, -1, false);
     } else {
-        return Result(lsrIter.orphanRemembered(), supportedLocales[suppIndex.value()],
-                      lsrIter.getBestDesiredIndex(), suppIndex.value(), true);
+        return Result(lsrIter.orphanRemembered(), supportedLocales[*suppIndex],
+                      lsrIter.getBestDesiredIndex(), *suppIndex, true);
     }
 }
 

icu4c/source/common/uloc.cpp

@@ -1154,12 +1154,12 @@ std::optional<int16_t> _findIndex(const char* const* list, const char* key)
 U_CFUNC const char*
 uloc_getCurrentCountryID(const char* oldID){
     std::optional<int16_t> offset = _findIndex(DEPRECATED_COUNTRIES, oldID);
-    return offset.has_value() ? REPLACEMENT_COUNTRIES[offset.value()] : oldID;
+    return offset.has_value() ? REPLACEMENT_COUNTRIES[*offset] : oldID;
 }
 U_CFUNC const char*
 uloc_getCurrentLanguageID(const char* oldID){
     std::optional<int16_t> offset = _findIndex(DEPRECATED_LANGUAGES, oldID);
-    return offset.has_value() ? REPLACEMENT_LANGUAGES[offset.value()] : oldID;
+    return offset.has_value() ? REPLACEMENT_LANGUAGES[*offset] : oldID;
 }
 
 namespace {
@@ -1225,7 +1225,7 @@ _getLanguage(const char* localeID,
         buffer[3] = '\0';
         std::optional<int16_t> offset = _findIndex(LANGUAGES_3, buffer);
         if (offset.has_value()) {
-            const char* const alias = LANGUAGES[offset.value()];
+            const char* const alias = LANGUAGES[*offset];
             sink->Append(alias, (int32_t)uprv_strlen(alias));
             return;
         }
@@ -1306,7 +1306,7 @@ _getRegion(const char* localeID,
         buffer[3] = '\0';
         std::optional<int16_t> offset = _findIndex(COUNTRIES_3, buffer);
         if (offset.has_value()) {
-            const char* const alias = COUNTRIES[offset.value()];
+            const char* const alias = COUNTRIES[*offset];
             sink->Append(alias, (int32_t)uprv_strlen(alias));
             return;
         }
@@ -1465,10 +1465,10 @@ ulocimp_getSubtags(
 
     ulocimp_getSubtags(
             localeID,
-            languageSink.has_value() ? &languageSink.value() : nullptr,
-            scriptSink.has_value() ? &scriptSink.value() : nullptr,
-            regionSink.has_value() ? &regionSink.value() : nullptr,
-            variantSink.has_value() ? &variantSink.value() : nullptr,
+            languageSink.has_value() ? &*languageSink : nullptr,
+            scriptSink.has_value() ? &*scriptSink : nullptr,
+            regionSink.has_value() ? &*regionSink : nullptr,
+            variantSink.has_value() ? &*variantSink : nullptr,
             pEnd,
             status);
 }
@@ -2183,7 +2183,7 @@ uloc_getISO3Language(const char* localeID)
     if (U_FAILURE(err))
         return "";
     std::optional<int16_t> offset = _findIndex(LANGUAGES, lang.data());
-    return offset.has_value() ? LANGUAGES_3[offset.value()] : "";
+    return offset.has_value() ? LANGUAGES_3[*offset] : "";
 }
 
 U_CAPI const char*  U_EXPORT2
@@ -2199,7 +2199,7 @@ uloc_getISO3Country(const char* localeID)
     if (U_FAILURE(err))
         return "";
     std::optional<int16_t> offset = _findIndex(COUNTRIES, cntry.data());
-    return offset.has_value() ? COUNTRIES_3[offset.value()] : "";
+    return offset.has_value() ? COUNTRIES_3[*offset] : "";
 }
 
 U_CAPI uint32_t  U_EXPORT2

icu4c/source/test/depstest/dependencies.txt

@@ -139,12 +139,6 @@ group: cplusplus
     # "Calls the current terminate handler."
     std::terminate()
 
-    # ICU4C doesn't actually use C++ exceptions, but the standard library does,
-    # so these symbols can end up in debug builds.
-    "std::exception::~exception()"
-    "typeinfo for std::exception"
-    "vtable for std::exception"
-
 group: iostream
     "std::basic_ios<char, std::char_traits<char> >::clear(std::_Ios_Iostate)"
     "std::basic_ios<char, std::char_traits<char> >::eof() const"