[libc] Implemented wcscmp (#142423)

Implemented wcscmp and added tests

libc/test/src/wchar/CMakeLists.txt

@@ -55,6 +55,16 @@ add_libc_test(
     libc.src.wchar.wcschr
 )
 
+add_libc_test(
+  wcscmp_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcscmp_test.cpp
+  DEPENDS
+    libc.src.wchar.wcscmp
+)
+
 add_libc_test(
   wcspbrk_test
   SUITE

libc/test/src/wchar/wcscmp_test.cpp

@@ -0,0 +1,97 @@
+//===-- Unittests for wcscmp ----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/wchar/wcscmp.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWcscmpTest, EmptyStringsShouldReturnZero) {
+  const wchar_t *s1 = L"";
+  const wchar_t *s2 = L"";
+  int result = LIBC_NAMESPACE::wcscmp(s1, s2);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcscmp(s2, s1);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcWcscmpTest, EmptyStringShouldNotEqualNonEmptyString) {
+  const wchar_t *empty = L"";
+  const wchar_t *s2 = L"abc";
+  int result = LIBC_NAMESPACE::wcscmp(empty, s2);
+  ASSERT_LT(result, 0);
+
+  // Similar case if empty string is second argument.
+  const wchar_t *s3 = L"123";
+  result = LIBC_NAMESPACE::wcscmp(s3, empty);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcscmpTest, EqualStringsShouldReturnZero) {
+  const wchar_t *s1 = L"abc";
+  const wchar_t *s2 = L"abc";
+  int result = LIBC_NAMESPACE::wcscmp(s1, s2);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcscmp(s2, s1);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcWcscmpTest, ShouldReturnResultOfFirstDifference) {
+  const wchar_t *s1 = L"___B42__";
+  const wchar_t *s2 = L"___C55__";
+  int result = LIBC_NAMESPACE::wcscmp(s1, s2);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcscmp(s2, s1);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcscmpTest, CapitalizedLetterShouldNotBeEqual) {
+  const wchar_t *s1 = L"abcd";
+  const wchar_t *s2 = L"abCd";
+  int result = LIBC_NAMESPACE::wcscmp(s1, s2);
+  ASSERT_GT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcscmp(s2, s1);
+  ASSERT_LT(result, 0);
+}
+
+TEST(LlvmLibcWcscmpTest, UnequalLengthStringsShouldNotReturnZero) {
+  const wchar_t *s1 = L"abc";
+  const wchar_t *s2 = L"abcd";
+  int result = LIBC_NAMESPACE::wcscmp(s1, s2);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcscmp(s2, s1);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcscmpTest, StringArgumentSwapChangesSign) {
+  const wchar_t *a = L"a";
+  const wchar_t *b = L"b";
+  int result = LIBC_NAMESPACE::wcscmp(b, a);
+  ASSERT_GT(result, 0);
+
+  result = LIBC_NAMESPACE::wcscmp(a, b);
+  ASSERT_LT(result, 0);
+}
+
+#if defined(LIBC_ADD_NULL_CHECKS) && !defined(LIBC_HAS_SANITIZER)
+TEST(LlvmLibcWcscmpTest, NullptrCrash) {
+  // Passing in a nullptr should crash the program.
+  EXPECT_DEATH([] { LIBC_NAMESPACE::wcscmp(L"aaaaaaaaaaaaaa", nullptr); },
+               WITH_SIGNAL(-1));
+  EXPECT_DEATH([] { LIBC_NAMESPACE::wcscmp(nullptr, L"aaaaaaaaaaaaaa"); },
+               WITH_SIGNAL(-1));
+}
+#endif // LIBC_HAS_ADDRESS_SANITIZER