[libc] wcslcat implementation #146588

sribee8 · 2025-07-01T18:26:43Z

implemented wcslcat and tests.

llvmbot · 2025-07-01T18:27:18Z

@llvm/pr-subscribers-libc

Author: None (sribee8)

Changes

implemented wcslcat and tests.

Full diff: https://github.com/llvm/llvm-project/pull/146588.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/wcslcat.cpp (+39)
(added) libc/src/wchar/wcslcat.h (+23)
(modified) libc/test/src/wchar/CMakeLists.txt (+11)
(added) libc/test/src/wchar/wcslcat_test.cpp (+72)

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 59c248871f83a..1aa07f3750ca9 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -384,6 +384,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wcscat
     libc.src.wchar.wcsstr
     libc.src.wchar.wcsncat
+    libc.src.wchar.wcslcat
     libc.src.wchar.wcscpy
     libc.src.wchar.wmemchr
     libc.src.wchar.wcpcpy
diff --git a/libc/include/wchar.yaml b/libc/include/wchar.yaml
index 02e1ba331b7cc..0cf72ea923344 100644
--- a/libc/include/wchar.yaml
+++ b/libc/include/wchar.yaml
@@ -166,6 +166,14 @@ functions:
     arguments: 
       - type: wchar_t *__restrict
       - type: const wchar_t *__restrict
+  - name: wcslcat
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: wchar_t *__restrict
+      - type: const wchar_t *__restrict
+      - type: size_t
   - name: wcsstr
     standards:
       - stdc
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index f2f4b1d38f0f3..40d94576ac9e1 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -307,6 +307,18 @@ add_entrypoint_object(
     libc.src.string.string_utils
 )
 
+add_entrypoint_object(
+  wcslcat
+  SRCS
+    wcslcat.cpp
+  HDRS
+    wcslcat.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.wchar_macros
+    libc.src.string.string_utils
+)
+
 add_entrypoint_object(
   wmemchr
   SRCS
diff --git a/libc/src/wchar/wcslcat.cpp b/libc/src/wchar/wcslcat.cpp
new file mode 100644
index 0000000000000..eff3974f8dff8
--- /dev/null
+++ b/libc/src/wchar/wcslcat.cpp
@@ -0,0 +1,39 @@
+//===-- Implementation of wcslcat -----------------------------------------===//
+//
+// 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/wcslcat.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/string/string_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcslcat,
+                   (wchar_t *__restrict dst, const wchar_t *__restrict src,
+                    size_t dstsize)) {
+  size_t dstlen = internal::string_length(dst);
+  size_t srclen = internal::string_length(src);
+  size_t limit = dstsize - dstlen - 1;
+
+  if (static_cast<int>(limit) < 0)
+    return (dstsize < dstlen ? dstsize : dstlen) + srclen;
+  size_t i = 0;
+  for (; i < limit && src[i] != L'\0'; ++i) {
+    dst[dstlen + i] = src[i];
+  }
+  
+  // appending null terminator if there is room
+  if (dstlen + i < dstlen + dstsize)
+    dst[dstlen + i] = L'\0';
+  return (dstsize < dstlen ? dstsize : dstlen) + srclen;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcslcat.h b/libc/src/wchar/wcslcat.h
new file mode 100644
index 0000000000000..fd964e1af49d5
--- /dev/null
+++ b/libc/src/wchar/wcslcat.h
@@ -0,0 +1,23 @@
+//===-- Implementation header for wcslcat ---------------------------------===//
+//
+// 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_WCSLCAT_H
+#define LLVM_LIBC_SRC_WCHAR_WCSLCAT_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+size_t wcslcat(wchar_t *__restrict dst, const wchar_t *__restrict src,
+               size_t dstsize);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSLCAT_H
diff --git a/libc/test/src/wchar/CMakeLists.txt b/libc/test/src/wchar/CMakeLists.txt
index 657343d072158..baae1e822e854 100644
--- a/libc/test/src/wchar/CMakeLists.txt
+++ b/libc/test/src/wchar/CMakeLists.txt
@@ -283,6 +283,17 @@ add_libc_test(
     libc.src.wchar.wcsncat
 )
 
+add_libc_test(
+  wcslcat_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcslcat_test.cpp
+  DEPENDS
+    libc.src.wchar.wcslcat
+    libc.hdr.types.size_t
+)
+
 add_libc_test(
   wcscpy_test
   SUITE
diff --git a/libc/test/src/wchar/wcslcat_test.cpp b/libc/test/src/wchar/wcslcat_test.cpp
new file mode 100644
index 0000000000000..34b5af7767346
--- /dev/null
+++ b/libc/test/src/wchar/wcslcat_test.cpp
@@ -0,0 +1,72 @@
+//===-- Unittests for wcslcat ---------------------------------------------===//
+//
+// 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 "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/wchar/wcslcat.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCSLCatTest, TooBig) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[4]{L"ab"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 3);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  // Should still return src length + dst length
+  ASSERT_EQ(res, size_t(4));
+  // Not enough space to copy d
+  res = LIBC_NAMESPACE::wcslcat(dst, src, 4);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  ASSERT_TRUE(dst[3] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}
+
+TEST(LlvmLibcWCSLCatTest, Smaller) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[7]{L"ab"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 7);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  ASSERT_TRUE(dst[3] == L'd');
+  ASSERT_TRUE(dst[4] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}
+
+TEST(LlvmLibcWCSLCatTest, SmallerNoOverwriteAfter0) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[8]{L"ab\0\0efg"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 8);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  ASSERT_TRUE(dst[3] == L'd');
+  ASSERT_TRUE(dst[4] == L'\0');
+  ASSERT_TRUE(dst[5] == L'f');
+  ASSERT_TRUE(dst[6] == L'g');
+  ASSERT_TRUE(dst[7] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}
+
+TEST(LlvmLibcWCSLCatTest, No0) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[7]{L"ab"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 1);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  ASSERT_EQ(res, size_t(3));
+  res = LIBC_NAMESPACE::wcslcat(dst, src, 2);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}

github-actions · 2025-07-01T18:29:03Z

✅ With the latest revision this PR passed the C/C++ code formatter.

uzairnawaz

LGTM

libc/src/wchar/wcslcat.cpp

libc/test/src/wchar/wcslcat_test.cpp

michaelrj-google · 2025-07-09T17:51:06Z

libc/src/wchar/wcslcat.cpp

+  const size_t dstlen = internal::string_length(dst);
+  const size_t srclen = internal::string_length(src);
+  int limit = static_cast<int>(dstsize - dstlen - 1);
+  size_t returnval = (dstsize < dstlen ? dstsize : dstlen) + srclen;
  if (static_cast<int>(limit) < 0)


this cast is now unncessary

[libc] wcslcat implementation

e151ed9

implemented wcslcat and tests.

llvmbot added the libc label Jul 1, 2025

added wcslcat to bazel files

7f69a1e

sribee8 requested review from rupprecht, keith and aaronmondal as code owners July 1, 2025 18:28

llvmbot added the bazel "Peripheral" support tier build system: utils/bazel label Jul 1, 2025

fixed formatting

40d20d1

sribee8 requested review from uzairnawaz and michaelrj-google July 1, 2025 18:30

uzairnawaz approved these changes Jul 8, 2025

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michaelrj-google reviewed Jul 8, 2025

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cleaned up code and tests

af7308b

michaelrj-google reviewed Jul 9, 2025

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[libc] wcslcat implementation #146588

[libc] wcslcat implementation #146588

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