[libc] Implemented wcsncmp (#142429)

Implemented wcsncmp and added tests

libc/test/src/wchar/CMakeLists.txt

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

libc/test/src/wchar/wcsncmp_test.cpp

@@ -0,0 +1,169 @@
+//===-- Unittests for wcsncmp ---------------------------------------------===//
+//
+// 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/wcsncmp.h"
+#include "test/UnitTest/Test.h"
+
+// This group is just copies of the wcscmp tests, since all the same cases still
+// need to be tested.
+
+TEST(LlvmLibcWcsncmpTest, EmptyStringsShouldReturnZeroWithSufficientLength) {
+  const wchar_t *s1 = L"";
+  const wchar_t *s2 = L"";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 1);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 1);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest,
+     EmptyStringShouldNotEqualNonEmptyStringWithSufficientLength) {
+  const wchar_t *empty = L"";
+  const wchar_t *s2 = L"abc";
+  int result = LIBC_NAMESPACE::wcsncmp(empty, s2, 3);
+  ASSERT_LT(result, 0);
+
+  // Similar case if empty string is second argument.
+  const wchar_t *s3 = L"123";
+  result = LIBC_NAMESPACE::wcsncmp(s3, empty, 3);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest, EqualStringsShouldReturnZeroWithSufficientLength) {
+  const wchar_t *s1 = L"abc";
+  const wchar_t *s2 = L"abc";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 3);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 3);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest,
+     ShouldReturnResultOfFirstDifferenceWithSufficientLength) {
+  const wchar_t *s1 = L"___B42__";
+  const wchar_t *s2 = L"___C55__";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 8);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 8);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest,
+     CapitalizedLetterShouldNotBeEqualWithSufficientLength) {
+  const wchar_t *s1 = L"abcd";
+  const wchar_t *s2 = L"abCd";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 4);
+  ASSERT_GT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 4);
+  ASSERT_LT(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest,
+     UnequalLengthStringsShouldNotReturnZeroWithSufficientLength) {
+  const wchar_t *s1 = L"abc";
+  const wchar_t *s2 = L"abcd";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 4);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 4);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest, StringArgumentSwapChangesSignWithSufficientLength) {
+  const wchar_t *a = L"a";
+  const wchar_t *b = L"b";
+  int result = LIBC_NAMESPACE::wcsncmp(b, a, 1);
+  ASSERT_GT(result, 0);
+
+  result = LIBC_NAMESPACE::wcsncmp(a, b, 1);
+  ASSERT_LT(result, 0);
+}
+
+#if defined(LIBC_ADD_NULL_CHECKS) && !defined(LIBC_HAS_SANITIZER)
+TEST(LlvmLibcWcsncmpTest, NullptrCrash) {
+  // Passing in a nullptr should crash the program.
+  EXPECT_DEATH([] { LIBC_NAMESPACE::wcsncmp(L"aaaaaaaaaaaaaa", nullptr, 3); },
+               WITH_SIGNAL(-1));
+  EXPECT_DEATH([] { LIBC_NAMESPACE::wcsncmp(nullptr, L"aaaaaaaaaaaaaa", 3); },
+               WITH_SIGNAL(-1));
+}
+#endif // LIBC_HAS_ADDRESS_SANITIZER
+
+// This group is actually testing wcsncmp functionality
+
+TEST(LlvmLibcWcsncmpTest, NonEqualStringsEqualWithLengthZero) {
+  const wchar_t *s1 = L"abc";
+  const wchar_t *s2 = L"def";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 0);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 0);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest, NonEqualStringsNotEqualWithLengthOne) {
+  const wchar_t *s1 = L"abc";
+  const wchar_t *s2 = L"def";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 1);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 1);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest, NonEqualStringsEqualWithShorterLength) {
+  const wchar_t *s1 = L"___B42__";
+  const wchar_t *s2 = L"___C55__";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 3);
+  ASSERT_EQ(result, 0);
+
+  // This should return 'B' - 'C' = -1.
+  result = LIBC_NAMESPACE::wcsncmp(s1, s2, 4);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 3);
+  ASSERT_EQ(result, 0);
+
+  // This should return 'C' - 'B' = 1.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 4);
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest, StringComparisonEndsOnNullByteEvenWithLongerLength) {
+  const wchar_t *s1 = L"abc\0def";
+  const wchar_t *s2 = L"abc\0abc";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 7);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 7);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcWcsncmpTest, Case) {
+  const wchar_t *s1 = L"aB";
+  const wchar_t *s2 = L"ab";
+  int result = LIBC_NAMESPACE::wcsncmp(s1, s2, 2);
+  ASSERT_LT(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::wcsncmp(s2, s1, 2);
+  ASSERT_GT(result, 0);
+}