[libc] Implement wcs to mbs family of functions #149421

uzairnawaz · 2025-07-17T22:57:30Z

Implemented internal wcs to mbs internal function + tests
Impelemented wcs to mbs public functions

github-actions · 2025-07-17T22:59:57Z

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

llvmbot · 2025-07-18T15:38:29Z

@llvm/pr-subscribers-libc

Author: Uzair Nawaz (uzairnawaz)

Changes

Implemented internal wcs to mbs internal function + tests
Impelemented wcs to mbs public functions

Patch is 35.83 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/149421.diff

18 Files Affected:

(modified) libc/config/linux/x86_64/entrypoints.txt (+3)
(modified) libc/include/wchar.yaml (+28)
(modified) libc/src/__support/wchar/CMakeLists.txt (+19)
(added) libc/src/__support/wchar/wcsnrtombs.cpp (+56)
(added) libc/src/__support/wchar/wcsnrtombs.h (+27)
(modified) libc/src/wchar/CMakeLists.txt (+41)
(added) libc/src/wchar/wcsnrtombs.cpp (+39)
(added) libc/src/wchar/wcsnrtombs.h (+23)
(added) libc/src/wchar/wcsrtombs.cpp (+39)
(added) libc/src/wchar/wcsrtombs.h (+23)
(added) libc/src/wchar/wcstombs.cpp (+37)
(added) libc/src/wchar/wcstombs.h (+22)
(modified) libc/test/src/__support/wchar/CMakeLists.txt (+17)
(added) libc/test/src/__support/wchar/wcsnrtombs_test.cpp (+190)
(modified) libc/test/src/wchar/CMakeLists.txt (+40)
(added) libc/test/src/wchar/wcsnrtombs_test.cpp (+156)
(added) libc/test/src/wchar/wcsrtombs_test.cpp (+113)
(added) libc/test/src/wchar/wcstombs_test.cpp (+85)

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 9223911f04a93..a067e73e80d13 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -1263,6 +1263,9 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.wchar.mbtowc
     libc.src.wchar.wcrtomb
     libc.src.wchar.wctomb
+    libc.src.wchar.wcstombs
+    libc.src.wchar.wcsrtombs
+    libc.src.wchar.wcsnrtombs
   )
 endif()
 
diff --git a/libc/include/wchar.yaml b/libc/include/wchar.yaml
index 123d3440aeec3..8c72e1963a425 100644
--- a/libc/include/wchar.yaml
+++ b/libc/include/wchar.yaml
@@ -274,3 +274,31 @@ functions:
       - type: const wchar_t *__restrict
       - type: wchar_t **__restrict
       - type: int
+  - name: wcstombs
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: char *__restrict
+      - type: const wchar_t *__restrict
+      - type: size_t
+  - name: wcsrtombs
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: char *__restrict
+      - type: const wchar_t **__restrict
+      - type: size_t
+      - type: mbstate_t
+  - name: wcsnrtombs
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: char *__restrict
+      - type: const wchar_t **__restrict
+      - type: size_t
+      - type: size_t
+      - type: mbstate_t
+
diff --git a/libc/src/__support/wchar/CMakeLists.txt b/libc/src/__support/wchar/CMakeLists.txt
index 802441d37fe92..b9efe5888d955 100644
--- a/libc/src/__support/wchar/CMakeLists.txt
+++ b/libc/src/__support/wchar/CMakeLists.txt
@@ -68,3 +68,22 @@ add_object_library(
   .character_converter
   .mbstate
 )
+
+add_object_library(
+  wcsnrtombs
+  HDRS
+    wcsnrtombs.h
+  SRCS 
+    wcsnrtombs.cpp
+  DEPENDS
+    libc.hdr.errno_macros
+    libc.hdr.types.char8_t
+    libc.hdr.types.char32_t
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.__support.error_or
+    libc.src.__support.common
+    .string_converter
+    .character_converter
+    .mbstate
+)
diff --git a/libc/src/__support/wchar/wcsnrtombs.cpp b/libc/src/__support/wchar/wcsnrtombs.cpp
new file mode 100644
index 0000000000000..b7add66214b5a
--- /dev/null
+++ b/libc/src/__support/wchar/wcsnrtombs.cpp
@@ -0,0 +1,56 @@
+//===-- Implementation of wcsnrtombs --------------------------------------===//
+//
+// 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/__support/wchar/wcsnrtombs.h"
+
+#include "hdr/types/char32_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/string_converter.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+ErrorOr<size_t> wcsnrtombs(char *__restrict s, const wchar_t **__restrict pwcs,
+                           size_t nwc, size_t len, mbstate *ps) {
+  CharacterConverter cr(ps);
+  if (!cr.isValidState())
+    return Error(EINVAL);
+
+  if (s == nullptr)
+    len = SIZE_MAX;
+
+  StringConverter<char32_t> str_conv(reinterpret_cast<const char32_t *>(*pwcs),
+                                     ps, len, nwc);
+  size_t dst_idx = 0;
+  ErrorOr<char8_t> converted = str_conv.popUTF8();
+  while (converted.has_value()) {
+    if (s != nullptr)
+      s[dst_idx] = converted.value();
+
+    if (converted.value() == '\0') {
+      *pwcs = nullptr;
+      return dst_idx;
+    }
+
+    dst_idx++;
+    converted = str_conv.popUTF8();
+  }
+
+  *pwcs += str_conv.getSourceIndex();
+  if (converted.error() == -1) // if we hit conversion limit
+    return dst_idx;
+
+  return Error(converted.error());
+}
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/__support/wchar/wcsnrtombs.h b/libc/src/__support/wchar/wcsnrtombs.h
new file mode 100644
index 0000000000000..f5ba910940692
--- /dev/null
+++ b/libc/src/__support/wchar/wcsnrtombs.h
@@ -0,0 +1,27 @@
+//===-- Implementation header for wcsnrtombs ------------------------------===//
+//
+// 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__SUPPORT_WCHAR_WCSNRTOMBS_H
+#define LLVM_LIBC_SRC__SUPPORT_WCHAR_WCSNRTOMBS_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/wchar/mbstate.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+ErrorOr<size_t> wcsnrtombs(char *__restrict s, const wchar_t **__restrict pwcs,
+                           size_t nwc, size_t len, mbstate *ps);
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC__SUPPORT_WCHAR_WCSNRTOMBS_H
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index 7ace1a6ca66ba..05c91d459bb95 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -159,6 +159,47 @@ add_entrypoint_object(
     libc.src.__support.wchar.mbstate
 )
 
+add_entrypoint_object(
+  wcstombs
+  SRCS
+    wcstombs.cpp
+  HDRS
+    wcstombs.h
+  DEPENDS
+    libc.hdr.types.wchar_t
+    libc.src.__support.wchar.mbstate
+    libc.src.__support.wchar.wcsnrtombs
+    libc.src.__support.libc_errno
+)
+
+add_entrypoint_object(
+  wcsrtombs
+  SRCS
+    wcsrtombs.cpp
+  HDRS
+    wcsrtombs.h
+  DEPENDS
+    libc.hdr.types.wchar_t
+    libc.hdr.types.mbstate_t
+    libc.src.__support.wchar.mbstate
+    libc.src.__support.wchar.wcsnrtombs
+    libc.src.__support.libc_errno
+)
+
+add_entrypoint_object(
+  wcsnrtombs
+  SRCS
+    wcsnrtombs.cpp
+  HDRS
+    wcsnrtombs.h
+  DEPENDS
+    libc.hdr.types.wchar_t
+    libc.hdr.types.mbstate_t
+    libc.src.__support.wchar.mbstate
+    libc.src.__support.wchar.wcsnrtombs
+    libc.src.__support.libc_errno
+)
+
 add_entrypoint_object(
   wmemset
   SRCS
diff --git a/libc/src/wchar/wcsnrtombs.cpp b/libc/src/wchar/wcsnrtombs.cpp
new file mode 100644
index 0000000000000..fd4724150e927
--- /dev/null
+++ b/libc/src/wchar/wcsnrtombs.cpp
@@ -0,0 +1,39 @@
+//===-- Implementation of wcsnrtombs --------------------------------------===//
+//
+// 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/wcsnrtombs.h"
+
+#include "hdr/types/char32_t.h"
+#include "hdr/types/mbstate_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/wcsnrtombs.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcsnrtombs,
+                   (char *__restrict s, const wchar_t **__restrict pwcs,
+                    size_t nwc, size_t len, mbstate_t *ps)) {
+  static internal::mbstate internal_mbstate;
+  auto result = internal::wcsnrtombs(
+      s, pwcs, nwc, len,
+      ps == nullptr ? &internal_mbstate
+                    : reinterpret_cast<internal::mbstate *>(ps));
+  if (!result.has_value()) {
+    libc_errno = result.error();
+    return -1;
+  }
+
+  return result.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcsnrtombs.h b/libc/src/wchar/wcsnrtombs.h
new file mode 100644
index 0000000000000..793d383660f1b
--- /dev/null
+++ b/libc/src/wchar/wcsnrtombs.h
@@ -0,0 +1,23 @@
+//===-- Implementation header for wcsnrtombs -------------------------------===//
+//
+// 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_WCSNRTOMBS_H
+#define LLVM_LIBC_SRC_WCHAR_WCSNRTOMBS_H
+
+#include "hdr/types/mbstate_t.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 wcsnrtombs(char *__restrict s, const wchar_t **__restrict pwcs, size_t nwc, size_t len, mbstate_t* ps);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSNRTOMBS_H
diff --git a/libc/src/wchar/wcsrtombs.cpp b/libc/src/wchar/wcsrtombs.cpp
new file mode 100644
index 0000000000000..b4632a4a436ba
--- /dev/null
+++ b/libc/src/wchar/wcsrtombs.cpp
@@ -0,0 +1,39 @@
+//===-- Implementation of wcsrtombs ---------------------------------------===//
+//
+// 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/wcsrtombs.h"
+
+#include "hdr/types/char32_t.h"
+#include "hdr/types/mbstate_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/wcsnrtombs.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcsrtombs,
+                   (char *__restrict s, const wchar_t **__restrict pwcs,
+                    size_t n, mbstate_t *ps)) {
+  static internal::mbstate internal_mbstate;
+  auto result = internal::wcsnrtombs(
+      s, pwcs, SIZE_MAX, n,
+      ps == nullptr ? &internal_mbstate
+                    : reinterpret_cast<internal::mbstate *>(ps));
+  if (!result.has_value()) {
+    libc_errno = result.error();
+    return -1;
+  }
+
+  return result.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcsrtombs.h b/libc/src/wchar/wcsrtombs.h
new file mode 100644
index 0000000000000..af69fccdb296a
--- /dev/null
+++ b/libc/src/wchar/wcsrtombs.h
@@ -0,0 +1,23 @@
+//===-- Implementation header for wcsrtombs --------------------------------===//
+//
+// 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_WCSRTOMBS_H
+#define LLVM_LIBC_SRC_WCHAR_WCSRTOMBS_H
+
+#include "hdr/types/mbstate_t.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 wcsrtombs(char *__restrict s, const wchar_t **__restrict pwcs, size_t n, mbstate_t* ps);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSRTOMBS_H
diff --git a/libc/src/wchar/wcstombs.cpp b/libc/src/wchar/wcstombs.cpp
new file mode 100644
index 0000000000000..28e2425d645e7
--- /dev/null
+++ b/libc/src/wchar/wcstombs.cpp
@@ -0,0 +1,37 @@
+//===-- Implementation of wcstombs ----------------------------------------===//
+//
+// 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/wcstombs.h"
+
+#include "hdr/types/char32_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/wcsnrtombs.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcstombs,
+                   (char *__restrict s, const wchar_t *__restrict wcs,
+                    size_t n)) {
+  static internal::mbstate internal_mbstate;
+  const wchar_t *wcs_ptr_copy = wcs;
+  auto result =
+      internal::wcsnrtombs(s, &wcs_ptr_copy, SIZE_MAX, n, &internal_mbstate);
+  if (!result.has_value()) {
+    libc_errno = result.error();
+    return -1;
+  }
+
+  return result.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcstombs.h b/libc/src/wchar/wcstombs.h
new file mode 100644
index 0000000000000..cd0008a168d90
--- /dev/null
+++ b/libc/src/wchar/wcstombs.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for wcstombs --------------------------------===//
+//
+// 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_WCSTOMBS_H
+#define LLVM_LIBC_SRC_WCHAR_WCSTOMBS_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 wcstombs(char *__restrict s, const wchar_t *__restrict pwcs, size_t n);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSTOMBS_H
diff --git a/libc/test/src/__support/wchar/CMakeLists.txt b/libc/test/src/__support/wchar/CMakeLists.txt
index f0727451736f9..c112c83dbe9af 100644
--- a/libc/test/src/__support/wchar/CMakeLists.txt
+++ b/libc/test/src/__support/wchar/CMakeLists.txt
@@ -34,3 +34,20 @@ add_libc_test(
     libc.hdr.errno_macros
     libc.hdr.types.char32_t
 )
+
+add_libc_test(
+  wcsnrtombs_test
+  SUITE
+    libc-support-tests
+  SRCS
+    wcsnrtombs_test.cpp
+  DEPENDS
+    libc.src.__support.wchar.string_converter
+    libc.src.__support.wchar.character_converter
+    libc.src.__support.wchar.mbstate
+    libc.src.__support.error_or
+    libc.src.__support.wchar.wcsnrtombs
+    libc.hdr.errno_macros
+    libc.hdr.types.char32_t
+    libc.hdr.types.char8_t
+)
diff --git a/libc/test/src/__support/wchar/wcsnrtombs_test.cpp b/libc/test/src/__support/wchar/wcsnrtombs_test.cpp
new file mode 100644
index 0000000000000..710fc4b568ac0
--- /dev/null
+++ b/libc/test/src/__support/wchar/wcsnrtombs_test.cpp
@@ -0,0 +1,190 @@
+//===-- Unittests for wcsnrtombs ------------------------------------------===//
+//
+// 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/errno_macros.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/error_or.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/wcsnrtombs.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWcsnrtombs, AllMultibyteLengths) {
+  LIBC_NAMESPACE::internal::mbstate state;
+
+  /// clown emoji, sigma symbol, y with diaeresis, letter A
+  const wchar_t src[] = {static_cast<wchar_t>(0x1f921),
+                         static_cast<wchar_t>(0x2211),
+                         static_cast<wchar_t>(0xff), static_cast<wchar_t>(0x41),
+                         static_cast<wchar_t>(0x0)};
+  const wchar_t *cur = src;
+  char mbs[11];
+
+  auto res = LIBC_NAMESPACE::internal::wcsnrtombs(mbs, &cur, 5, 11, &state);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(10));
+  ASSERT_EQ(cur, nullptr);
+  ASSERT_EQ(mbs[0], '\xF0'); // clown begin
+  ASSERT_EQ(mbs[1], '\x9F');
+  ASSERT_EQ(mbs[2], '\xA4');
+  ASSERT_EQ(mbs[3], '\xA1');
+  ASSERT_EQ(mbs[4], '\xE2'); // sigma begin
+  ASSERT_EQ(mbs[5], '\x88');
+  ASSERT_EQ(mbs[6], '\x91');
+  ASSERT_EQ(mbs[7], '\xC3'); // y diaeresis begin
+  ASSERT_EQ(mbs[8], '\xBF');
+  ASSERT_EQ(mbs[9], '\x41'); // A begin
+  ASSERT_EQ(mbs[10], '\0');  // null terminator
+}
+
+TEST(LlvmLibcWcsnrtombs, DestLimit) {
+  LIBC_NAMESPACE::internal::mbstate state1;
+
+  /// clown emoji, sigma symbol, y with diaeresis, letter A
+  const wchar_t src[] = {static_cast<wchar_t>(0x1f921),
+                         static_cast<wchar_t>(0x2211),
+                         static_cast<wchar_t>(0xff), static_cast<wchar_t>(0x41),
+                         static_cast<wchar_t>(0x0)};
+  const wchar_t *cur = src;
+
+  char mbs[11];
+  for (int i = 0; i < 11; ++i)
+    mbs[i] = '\x01'; // dummy initial values
+
+  auto res = LIBC_NAMESPACE::internal::wcsnrtombs(mbs, &cur, 5, 4, &state1);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(4));
+  ASSERT_EQ(cur, src + 1);
+  ASSERT_EQ(mbs[0], '\xF0');
+  ASSERT_EQ(mbs[1], '\x9F');
+  ASSERT_EQ(mbs[2], '\xA4');
+  ASSERT_EQ(mbs[3], '\xA1');
+  ASSERT_EQ(mbs[4], '\x01'); // didn't write more than 4 bytes
+
+  for (int i = 0; i < 11; ++i)
+    mbs[i] = '\x01'; // dummy initial values
+  LIBC_NAMESPACE::internal::mbstate state2;
+
+  // not enough bytes to convert the second character, so only converts one
+  cur = src;
+  res = LIBC_NAMESPACE::internal::wcsnrtombs(mbs, &cur, 5, 6, &state2);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(4));
+  ASSERT_EQ(cur, src + 1);
+  ASSERT_EQ(mbs[0], '\xF0');
+  ASSERT_EQ(mbs[1], '\x9F');
+  ASSERT_EQ(mbs[2], '\xA4');
+  ASSERT_EQ(mbs[3], '\xA1');
+  ASSERT_EQ(mbs[4], '\x01');
+}
+
+TEST(LlvmLibcWcsnrtombs, SrcLimit) {
+  LIBC_NAMESPACE::internal::mbstate state;
+
+  /// clown emoji, sigma symbol, y with diaeresis, letter A
+  const wchar_t src[] = {static_cast<wchar_t>(0x1f921),
+                         static_cast<wchar_t>(0x2211),
+                         static_cast<wchar_t>(0xff), static_cast<wchar_t>(0x41),
+                         static_cast<wchar_t>(0x0)};
+  const wchar_t *cur = src;
+
+  char mbs[11];
+  for (int i = 0; i < 11; ++i)
+    mbs[i] = '\x01'; // dummy initial values
+
+  auto res = LIBC_NAMESPACE::internal::wcsnrtombs(mbs, &cur, 2, 11, &state);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(7));
+  ASSERT_EQ(cur, src + 2);
+  ASSERT_EQ(mbs[0], '\xF0'); // clown begin
+  ASSERT_EQ(mbs[1], '\x9F');
+  ASSERT_EQ(mbs[2], '\xA4');
+  ASSERT_EQ(mbs[3], '\xA1');
+  ASSERT_EQ(mbs[4], '\xE2'); // sigma begin
+  ASSERT_EQ(mbs[5], '\x88');
+  ASSERT_EQ(mbs[6], '\x91');
+  ASSERT_EQ(mbs[7], '\x01');
+
+  res = LIBC_NAMESPACE::internal::wcsnrtombs(mbs + res.value(), &cur, 100, 11, &state);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(3));
+  ASSERT_EQ(cur, nullptr);
+  ASSERT_EQ(mbs[0], '\xF0'); // clown begin
+  ASSERT_EQ(mbs[1], '\x9F');
+  ASSERT_EQ(mbs[2], '\xA4');
+  ASSERT_EQ(mbs[3], '\xA1');
+  ASSERT_EQ(mbs[4], '\xE2'); // sigma begin
+  ASSERT_EQ(mbs[5], '\x88');
+  ASSERT_EQ(mbs[6], '\x91');
+  ASSERT_EQ(mbs[7], '\xC3'); // y diaeresis begin
+  ASSERT_EQ(mbs[8], '\xBF');
+  ASSERT_EQ(mbs[9], '\x41'); // A begin
+  ASSERT_EQ(mbs[10], '\0');  // null terminator
+}
+
+TEST(LlvmLibcWcsnrtombs, NullDest) {
+  LIBC_NAMESPACE::internal::mbstate state1;
+
+  const wchar_t src[] = {static_cast<wchar_t>(0x1f921),
+                         static_cast<wchar_t>(0x2211),
+                         static_cast<wchar_t>(0xff), static_cast<wchar_t>(0x41),
+                         static_cast<wchar_t>(0x0)};
+  const wchar_t *cur = src;
+
+  // n parameter ignored when dest is null
+  auto res = LIBC_NAMESPACE::internal::wcsnrtombs(nullptr, &cur, 5, 1, &state1);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(10));
+  ASSERT_EQ(cur, nullptr);
+
+  LIBC_NAMESPACE::internal::mbstate state2;
+  cur = src;
+  res = LIBC_NAMESPACE::internal::wcsnrtombs(nullptr, &cur, 5, 100, &state2);
+  ASSERT_TRUE(res.has_value());
+  ASSERT_EQ(res.value(), static_cast<size_t>(10));
+  ASSERT_EQ(cur, nullptr);
+}
+
+TEST(LlvmLib...
[truncated]

libc/src/__support/wchar/wcsnrtombs.cpp

libc/src/__support/wchar/wcsnrtombs.h

libc/test/src/__support/wchar/wcsnrtombs_test.cpp

michaelrj-google

Overall LGTM with some nits

libc/src/__support/wchar/wcsnrtombs.h

libc/include/wchar.yaml

libc/test/src/wchar/wcsrtombs_test.cpp

Implemented internal wcs to mbs internal function + tests Impelemented wcs to mbs public functions

uzairnawaz added 10 commits July 16, 2025 16:40

implemented public functions

953eca5

wcstombs test

d4a86b2

wcsrtombs tests

586497d

created internal function

7445bf7

Merge branch 'main' into wcstombs-functions

efac57f

Merge branch 'main' into wcstombs-functions

e2be69a

add invalid state test

843c79a

public string functions + tests

69ed44c

yaml typo

f01702a

typo

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uzairnawaz requested a review from sribee8 July 17, 2025 22:57

uzairnawaz added the libc label Jul 18, 2025

lntue reviewed Jul 18, 2025

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uzairnawaz added 4 commits July 18, 2025 16:52

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uzairnawaz added 2 commits July 18, 2025 19:46

added tests for src == null and mbstate == null

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mssing headers for death tests

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uzairnawaz added 2 commits July 18, 2025 21:49

added macro for death tests

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exclude windows

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lntue approved these changes Jul 21, 2025

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uzairnawaz added 2 commits July 21, 2025 13:20

Merge branch 'main' into wcstombs-functions

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uzairnawaz added 4 commits July 22, 2025 22:57

descriptive names; alphabetized yaml; used memset in tests

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formatting

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Merge branch 'main' into wcstombs-functions

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Merge branch 'main' into wcstombs-functions

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uzairnawaz merged commit 7884c07 into llvm:main Jul 24, 2025
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mahesh-attarde pushed a commit to mahesh-attarde/llvm-project that referenced this pull request Jul 28, 2025

[libc] Implement wcs to mbs family of functions (llvm#149421)

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Implemented internal wcs to mbs internal function + tests Impelemented wcs to mbs public functions

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