[libc-commits] [libc] [libc] Implemented wcsncmp (PR #142429)
via libc-commits
libc-commits at lists.llvm.org
Mon Jun 2 09:48:24 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libc
Author: Uzair Nawaz (uzairnawaz)
<details>
<summary>Changes</summary>
Implemented wcsncmp and added tests
---
Full diff: https://github.com/llvm/llvm-project/pull/142429.diff
7 Files Affected:
- (modified) libc/config/linux/x86_64/entrypoints.txt (+1)
- (modified) libc/include/wchar.yaml (+8)
- (modified) libc/src/wchar/CMakeLists.txt (+12)
- (added) libc/src/wchar/wcsncmp.cpp (+37)
- (added) libc/src/wchar/wcsncmp.h (+22)
- (modified) libc/test/src/wchar/CMakeLists.txt (+10)
- (added) libc/test/src/wchar/wcsncmp_test.cpp (+169)
``````````diff
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 545b9227349fe..d78fd646d9f5d 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/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.wcsncmp
libc.src.wchar.wcspbrk
libc.src.wchar.wcsspn
libc.src.wchar.wmemcmp
diff --git a/libc/include/wchar.yaml b/libc/include/wchar.yaml
index bfd9a10342019..f1a92268b3f72 100644
--- a/libc/include/wchar.yaml
+++ b/libc/include/wchar.yaml
@@ -42,6 +42,14 @@ functions:
arguments:
- type: const wchar_t *
- type: wchar_t
+ - name: wcsncmp
+ standards:
+ - stdc
+ return_type: int
+ arguments:
+ - type: const wchar_t *
+ - type: const wchar_t *
+ - type: size_t
- name: wcspbrk
standards:
- stdc
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index 9db121762348b..86065791baf98 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -68,6 +68,18 @@ add_entrypoint_object(
libc.src.__support.wctype_utils
)
+add_entrypoint_object(
+ wcsncmp
+ SRCS
+ wcsncmp.cpp
+ HDRS
+ wcsncmp.h
+ DEPENDS
+ libc.hdr.wchar_macros
+ libc.hdr.types.size_t
+ libc.src.__support.wctype_utils
+)
+
add_entrypoint_object(
wcsspn
SRCS
diff --git a/libc/src/wchar/wcsncmp.cpp b/libc/src/wchar/wcsncmp.cpp
new file mode 100644
index 0000000000000..f2e052b3c9fe3
--- /dev/null
+++ b/libc/src/wchar/wcsncmp.cpp
@@ -0,0 +1,37 @@
+//===-- Implementation of 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 "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, wcsncmp,
+ (const wchar_t *left, const wchar_t *right, size_t n)) {
+ LIBC_CRASH_ON_NULLPTR(left);
+ LIBC_CRASH_ON_NULLPTR(right);
+
+ if (n == 0)
+ return 0;
+
+ auto comp = [](wchar_t l, wchar_t r) -> int { return l - r; };
+
+ for (; n > 1; --n, ++left, ++right) {
+ wchar_t lc = *left;
+ if (!comp(lc, '\0') || comp(lc, *right))
+ break;
+ }
+ return comp(*reinterpret_cast<const wchar_t *>(left),
+ *reinterpret_cast<const wchar_t *>(right));
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcsncmp.h b/libc/src/wchar/wcsncmp.h
new file mode 100644
index 0000000000000..0b4187e730e28
--- /dev/null
+++ b/libc/src/wchar/wcsncmp.h
@@ -0,0 +1,22 @@
+//===-- Implementation header 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_WCSNCMP_H
+#define LLVM_LIBC_SRC_WCHAR_WCSNCMP_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int wcsncmp(const wchar_t *left, const wchar_t *right, size_t n);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSNCMP_H
diff --git a/libc/test/src/wchar/CMakeLists.txt b/libc/test/src/wchar/CMakeLists.txt
index 9bc230e0bddf3..41fed323e019e 100644
--- a/libc/test/src/wchar/CMakeLists.txt
+++ b/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(
wcspbrk_test
SUITE
diff --git a/libc/test/src/wchar/wcsncmp_test.cpp b/libc/test/src/wchar/wcsncmp_test.cpp
new file mode 100644
index 0000000000000..28bbb52648226
--- /dev/null
+++ b/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);
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/142429
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