[libc] wcpcpy implementation

libc/config/linux/x86_64/entrypoints.txt

@@ -384,6 +384,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wcsncat
     libc.src.wchar.wcscpy
     libc.src.wchar.wmemchr
+    libc.src.wchar.wcpcpy
 
     # sys/uio.h entrypoints
     libc.src.sys.uio.writev

libc/include/wchar.yaml

@@ -157,3 +157,10 @@ functions:
     arguments:
       - type: wchar_t *__restrict
       - type: const wchar_t *__restrict
+  - name: wcpcpy
+    standards:
+      - stdc
+    return_type: wchar_t *
+    arguments:
+      - type: wchar_t *__restrict
+      - type: const wchar_t *__restrict

libc/src/wchar/CMakeLists.txt

@@ -45,6 +45,18 @@ add_entrypoint_object(
     libc.hdr.types.wchar_t
 )
 
+add_entrypoint_object(
+  wcpcpy
+  SRCS
+    wcpcpy.cpp
+  HDRS
+    wcpcpy.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.wchar_macros
+    libc.src.string.string_utils
+)
+
 add_entrypoint_object(
   wcschr
   SRCS

libc/src/wchar/wcpcpy.cpp

@@ -0,0 +1,29 @@
+//===-- Implementation of wcpcpy ------------------------------------------===//
+//
+// 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/wcpcpy.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(wchar_t *, wcpcpy,
+                   (wchar_t *__restrict s1, const wchar_t *__restrict s2)) {
+  size_t size = internal::string_length(s2);
+  __builtin_memcpy(s1, s2, (size + 1) * sizeof(wchar_t));
+  wchar_t *result = s1 + size;
+  if (result != nullptr)
+    return result;
+  return nullptr;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcpcpy.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for wcpcpy ----------------------------------===//
+//
+// 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_WCPCPY_H
+#define LLVM_LIBC_SRC_WCHAR_WCPCPY_H
+
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+wchar_t *wcpcpy(wchar_t *__restrict ws1, const wchar_t *__restrict ws2);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCPCPY_H

libc/test/src/wchar/CMakeLists.txt

@@ -204,3 +204,13 @@ add_libc_test(
   DEPENDS
     libc.src.wchar.wcscpy
 )
+
+add_libc_test(
+  wcpcpy_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcpcpy_test.cpp
+  DEPENDS
+    libc.src.wchar.wcpcpy
+)

libc/test/src/wchar/wcpcpy_test.cpp

@@ -0,0 +1,50 @@
+//===-- Unittests for wcpcpy ---------------------------------------------===//
+//
+// 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/wchar_t.h"
+#include "src/wchar/wcpcpy.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCPCpyTest, EmptySrc) {
+  // Empty src should lead to empty destination.
+  wchar_t dest[4] = {L'a', L'b', L'c', L'\0'};
+  const wchar_t *src = L"";
+  LIBC_NAMESPACE::wcpcpy(dest, src);
+  ASSERT_TRUE(dest[0] == src[0]);
+  ASSERT_TRUE(dest[0] == L'\0');
+}
+
+TEST(LlvmLibcWCPCpyTest, EmptyDest) {
+  // Empty dest should result in src
+  const wchar_t *src = L"abc";
+  wchar_t dest[4];
+  wchar_t *result = LIBC_NAMESPACE::wcpcpy(dest, src);
+  ASSERT_EQ(dest + 3, result);
+  ASSERT_TRUE(result[0] == L'\0');
+  ASSERT_TRUE(dest[0] == L'a');
+  ASSERT_TRUE(dest[1] == L'b');
+  ASSERT_TRUE(dest[2] == L'c');
+}
+
+TEST(LlvmLibcWCPCpyTest, OffsetDest) {
+  // Offsetting should result in a concatenation.
+  const wchar_t *src = L"abc";
+  wchar_t dest[7];
+  dest[0] = L'x';
+  dest[1] = L'y';
+  dest[2] = L'z';
+  wchar_t *result = LIBC_NAMESPACE::wcpcpy(dest + 3, src);
+  ASSERT_TRUE(dest[0] == L'x');
+  ASSERT_TRUE(dest[1] == L'y');
+  ASSERT_TRUE(dest[2] == L'z');
+  ASSERT_TRUE(dest[3] == src[0]);
+  ASSERT_TRUE(dest[4] == src[1]);
+  ASSERT_TRUE(dest[5] == src[2]);
+  ASSERT_TRUE(result[0] == L'\0');
+  ASSERT_EQ(dest + 6, result);
+}