[libc] Implemented wcscmp (llvm#142423)

Implemented wcscmp and added tests

Author: uzairnawaz

libc/config/linux/x86_64/entrypoints.txt

@@ -366,6 +366,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wctob
     libc.src.wchar.wmemset
     libc.src.wchar.wcschr
+    libc.src.wchar.wcscmp
     libc.src.wchar.wcspbrk
     libc.src.wchar.wcsspn
     libc.src.wchar.wmemcmp

libc/include/wchar.yaml

@@ -42,6 +42,13 @@ functions:
     arguments: 
       - type: const wchar_t *
       - type: wchar_t
+  - name: wcscmp
+    standards:
+      - stdc
+    return_type: int
+    arguments:
+      - type: const wchar_t *
+      - type: const wchar_t *
   - name: wcspbrk
     standards:
       - stdc

libc/src/wchar/CMakeLists.txt

@@ -57,6 +57,16 @@ add_entrypoint_object(
     libc.src.__support.wctype_utils
 )
 
+add_entrypoint_object(
+  wcscmp
+  SRCS
+    wcscmp.cpp
+  HDRS
+    wcscmp.h
+  DEPENDS
+    libc.hdr.wchar_macros
+)
+
 add_entrypoint_object(
   wcspbrk
   SRCS

libc/src/wchar/wcscmp.cpp

@@ -0,0 +1,30 @@
+//===-- Implementation of 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 "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/null_check.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, wcscmp, (const wchar_t *left, const wchar_t *right)) {
+  LIBC_CRASH_ON_NULLPTR(left);
+  LIBC_CRASH_ON_NULLPTR(right);
+
+  auto comp = [](wchar_t l, wchar_t r) -> int { return l - r; };
+
+  for (; *left && !comp(*left, *right); ++left, ++right)
+    ;
+
+  return comp(*left, *right);
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcscmp.h

@@ -0,0 +1,22 @@
+//===-- Implementation header 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_WCSCMP_H
+#define LLVM_LIBC_SRC_WCHAR_WCSCMP_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int wcscmp(const wchar_t *left, const wchar_t *right);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSCMP_H

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