ICU-23485 Fix tests

Author: FrankYFTang

icu4c/source/test/intltest/strcase.cpp

@@ -1848,40 +1848,34 @@ void StringCaseTest::TestCaseMapGreekExtended() {
 #endif
 }
 
-void StringCaseTest::TestCmpFoldStackBufferUnderflow() {
-    UErrorCode errorCode = U_ZERO_ERROR;
 
+void StringCaseTest::TestCmpFoldStackBufferUnderflow() {
     // Surrogate/Supplementary sequence constructed from V8 PoC targeting the _cmpFold boundary edge-case.
     // Includes a standalone lead surrogate followed immediately by a supplementary character case-folding trigger.
-    static const char16_t s1[] = {
+    static const char16_t s1_chars[] = {
         0xd801,          // Standalone / Intervening Lead Surrogate
         0xd801, 0xdc01,  // U+10401 (Lead + Trail) -> Generates 'fold' entry at absolute zero-index boundary
         0xd801, 0xdc01,
         0xdc02,          // Trail Surrogate boundary anchor
         0
     };
 
-    static const char16_t s2[] = {
+    static const char16_t s2_chars[] = {
         0xd801, 0xdc01,
         0xd801, 0xdc01,
         0xd801, 0xdc02,
         0
     };
 
-    // Execute u_strcmpFold. Under ASAN on an unpatched binary, this immediately
-    // triggers a stack-buffer-overflow read underflow at fold1[-1].
-    int32_t cmpResult = u_strcmpFold(
-        s1, -1,
-        s2, -1,
-        U_FOLD_CASE_DEFAULT,
-        &errorCode
-    );
+    // Construct immutable UnicodeString wrappers leveraging ICU's public C++ API.
+    icu::UnicodeString s1(false, s1_chars, -1);
+    icu::UnicodeString s2(false, s2_chars, -1);
 
-    // Assert that execution completes without error-state propagation and
-    // terminates deterministically, demonstrating robust stack-boundary enforcement.
-    assertSuccess("u_strcmpFold stack-underflow boundary check", errorCode);
+    // Execute the case-folded comparison. This internally delegates to the 
+    // version-renamed u_strcmpFold (and underlying _cmpFold), securely exercising the patched stack boundaries.
+    int8_t cmpResult = s1.caseCompare(s2, U_FOLD_CASE_DEFAULT);
 
-    // Result value utilized to enforce runtime evaluation
+    // Validate deterministic completion and memory-safety boundary execution.
     (void)cmpResult;
 }