[libc] Implemented wmemset and added tests #141691

uzairnawaz · 2025-05-27T23:51:34Z

Implemented and tests the wmemset function in libc.

github-actions · 2025-05-27T23:51:54Z

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llvmbot · 2025-05-27T23:52:26Z

@llvm/pr-subscribers-libc

Author: Uzair Nawaz (uzairnawaz)

Changes

Implemented and tests the wmemset function in libc.

Full diff: https://github.com/llvm/llvm-project/pull/141691.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/wmemset.cpp (+25)
(added) libc/src/wchar/wmemset.h (+23)
(modified) libc/test/src/wchar/CMakeLists.txt (+12)
(added) libc/test/src/wchar/wmemset_test.cpp (+89)

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 9f447dd0d35d2..6a0dafd20e828 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -364,6 +364,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.btowc
     libc.src.wchar.wcslen
     libc.src.wchar.wctob
+    libc.src.wchar.wmemset
 
     # sys/uio.h entrypoints
     libc.src.sys.uio.writev
diff --git a/libc/include/wchar.yaml b/libc/include/wchar.yaml
index 0ac9aa29f0a18..ad1b2e552f219 100644
--- a/libc/include/wchar.yaml
+++ b/libc/include/wchar.yaml
@@ -27,3 +27,11 @@ functions:
     return_type: wint_t
     arguments:
       - type: int
+  - name: wmemset
+    standards:
+      - stdc
+    return_type: wchar_t*
+    arguments:
+      - type: wchar_t*
+      - type: wchar_t
+      - type: size_t
\ No newline at end of file
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index 703db75b5b194..6cc6001f82db6 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -33,3 +33,15 @@ add_entrypoint_object(
     libc.hdr.wchar_macros
     libc.src.__support.wctype_utils
 )
+
+add_entrypoint_object(
+  wmemset
+  SRCS
+    wmemset.cpp
+  HDRS
+    wmemset.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.__support.wctype_utils
+)
diff --git a/libc/src/wchar/wmemset.cpp b/libc/src/wchar/wmemset.cpp
new file mode 100644
index 0000000000000..4b0c36db045b0
--- /dev/null
+++ b/libc/src/wchar/wmemset.cpp
@@ -0,0 +1,25 @@
+//===-- Implementation of wmemset -----------------------------------------===//
+//
+// 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/wmemset.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(wchar_t*, wmemset, (wchar_t *s, wchar_t c, size_t n)) {
+    for (size_t i = 0; i < n; i++) {
+        s[i] = c;
+    }
+    return s;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
+
diff --git a/libc/src/wchar/wmemset.h b/libc/src/wchar/wmemset.h
new file mode 100644
index 0000000000000..b7067aaa188e6
--- /dev/null
+++ b/libc/src/wchar/wmemset.h
@@ -0,0 +1,23 @@
+//===-- Implementation header for wmemset ----------------------------------===//
+//
+// 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_WMEMSET_H
+#define LLVM_LIBC_SRC_WCHAR_WMEMSET_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
+
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WMEMSET_H
diff --git a/libc/test/src/wchar/CMakeLists.txt b/libc/test/src/wchar/CMakeLists.txt
index d41e328fc9d90..e6eb51c8e8183 100644
--- a/libc/test/src/wchar/CMakeLists.txt
+++ b/libc/test/src/wchar/CMakeLists.txt
@@ -32,3 +32,15 @@ add_libc_test(
   DEPENDS
     libc.src.wchar.wctob
 )
+
+add_libc_test(
+  wmemset_test 
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wmemset_test.cpp
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.wchar.wmemset
+)
\ No newline at end of file
diff --git a/libc/test/src/wchar/wmemset_test.cpp b/libc/test/src/wchar/wmemset_test.cpp
new file mode 100644
index 0000000000000..19b8e1d95f8d0
--- /dev/null
+++ b/libc/test/src/wchar/wmemset_test.cpp
@@ -0,0 +1,89 @@
+//===-- Unittests for wmemset ---------------------------------------------===//
+//
+// 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/wmemset.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWMemsetTest, SmallStringBoundCheck) {
+  wchar_t* str = new wchar_t[5];
+  for (int i = 0; i < 5; i++) {
+    str[i] = 'A';
+  }
+
+  wchar_t* output = LIBC_NAMESPACE::wmemset(str + 1, 'B', 3);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  EXPECT_TRUE(str[1] == (wchar_t)'B');
+  EXPECT_TRUE(str[2] == (wchar_t)'B');
+  EXPECT_TRUE(str[3] == (wchar_t)'B');
+  EXPECT_TRUE(str[4] == (wchar_t)'A');
+}
+
+TEST(LlvmLibcWMemsetTest, LargeStringBoundCheck) {
+  const int str_size = 1000;
+  wchar_t* str = new wchar_t[str_size];
+  for (int i = 0; i < str_size; i++) {
+    str[i] = 'A';
+  }
+
+  wchar_t* output = LIBC_NAMESPACE::wmemset(str + 1, 'B', str_size - 2);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  for (int i = 1; i < str_size - 1; i++) {
+    EXPECT_TRUE(str[i] == (wchar_t)'B');
+  }
+  EXPECT_TRUE(str[str_size - 1] == (wchar_t)'A');
+}
+
+TEST(LlvmLibcWMemsetTest, WChar_Size_Small) {
+  // ensure we can handle 32 bit values 
+  wchar_t* str = new wchar_t[5];
+  const wchar_t magic = INT32_MAX;
+  
+  for (int i = 0; i < 5; i++) {
+    str[i] = 'A';
+  }
+
+  wchar_t* output = LIBC_NAMESPACE::wmemset(str + 1, magic, 3);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  EXPECT_TRUE(str[1] == magic);
+  EXPECT_TRUE(str[2] == magic);
+  EXPECT_TRUE(str[3] == magic);
+  EXPECT_TRUE(str[4] == (wchar_t)'A');
+}
+
+TEST(LlvmLibcWMemsetTest, WChar_Size_Large) {
+  // ensure we can handle 32 bit values 
+  const int str_size = 1000;
+  const wchar_t magic = INT32_MAX;
+  wchar_t* str = new wchar_t[str_size];
+  for (int i = 0; i < str_size; i++) {
+    str[i] = 'A';
+  }
+
+  wchar_t* output = LIBC_NAMESPACE::wmemset(str + 1, magic, str_size - 2);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  for (int i = 1; i < str_size - 1; i++) {
+    EXPECT_TRUE(str[i] == magic);
+  }
+  EXPECT_TRUE(str[str_size - 1] == (wchar_t)'A');
+}
+
+

github-actions · 2025-05-28T00:01:33Z

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

michaelrj-google

Looks good! Needs a couple changes but this is a good start.

michaelrj-google · 2025-05-27T23:59:22Z

libc/include/wchar.yaml

+    arguments:
+      - type: wchar_t*
+      - type: wchar_t
+      - type: size_t


nit: fix missing newline

michaelrj-google · 2025-05-28T00:00:32Z

libc/src/wchar/wmemset.cpp

+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(wchar_t*, wmemset, (wchar_t *s, wchar_t c, size_t n)) {
+    for (size_t i = 0; i < n; i++) {


The LLVM style recommends skipping braces on one-line for loops: https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

michaelrj-google · 2025-05-28T00:00:41Z

libc/test/src/wchar/CMakeLists.txt

+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.wchar.wmemset
+)


nit: fix missing newline

michaelrj-google · 2025-05-28T20:04:55Z

libc/src/wchar/wmemset.cpp

+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(wchar_t *, wmemset, (wchar_t * s, wchar_t c, size_t n)) {
+  for (size_t i = 0; i < n; i++) {


The LLVM coding standards recommend skipping the braces for one line for loops: https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

michaelrj-google · 2025-05-28T20:07:43Z

libc/test/src/wchar/wmemset_test.cpp

+}
+
+TEST(LlvmLibcWMemsetTest, LargeStringBoundCheck) {
+  const int str_size = 1000;


nit: make this constexpr

Suggested change

const int str_size = 1000;

constexpr int STR_SIZE = 1000;

michaelrj-google · 2025-05-28T20:18:23Z

libc/test/src/wchar/wmemset_test.cpp

+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWMemsetTest, SmallStringBoundCheck) {
+  wchar_t *str = new wchar_t[5];


If you use new here that puts the data on the heap. When possible, it's preferred to put test variables on the stack to simplify memory management. To do that you define the variable as a local array instead of just a pointer.

Same recommendation on all these tests, but for simplicity I'm just marking this one.

Suggested change

wchar_t *str = new wchar_t[5];

wchar_t str[5];

michaelrj-google · 2025-05-28T20:26:18Z

libc/test/src/wchar/wmemset_test.cpp

+TEST(LlvmLibcWMemsetTest, WChar_Size_Small) {
+  // ensure we can handle 32 bit values
+  wchar_t *str = new wchar_t[5];
+  const wchar_t magic = INT32_MAX;


it's not necessarily safe to assume wchar_t is 32 bits. Instead it's better to use the provided WCHAR_MAX macro.

It would also be good to give magic a more descriptive name.

Suggested change

const wchar_t magic = INT32_MAX;

const wchar_t magic = WCHAR_MAX;

michaelrj-google

LGTM, good job! Planning to merge this tomorrow after the presubmits are done.

michaelrj-google · 2025-05-29T17:31:46Z

The test failure is unrelated, merging.

github-actions · 2025-05-29T17:32:14Z

@uzairnawaz Congratulations on having your first Pull Request (PR) merged into the LLVM Project!

Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR.

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Implemented and tests the wmemset function in libc.

uzairnawaz added 2 commits May 27, 2025 22:20

wmemset complete; TODO look into build issue

7494a42

updated tests to avoid using expect_eq on widechars

da350d3

llvmbot added the libc label May 27, 2025

michaelrj-google self-requested a review May 27, 2025 23:59

formatting fix

2860250

michaelrj-google reviewed May 28, 2025

View reviewed changes

uzairnawaz added 4 commits May 28, 2025 21:16

moved test strings to the stack; fixed style issues

7592ccb

Merge branch 'main' into wmemset

472589a

style fix

c1670df

format fix in wmemset_test

02dd7c8

michaelrj-google approved these changes May 28, 2025

View reviewed changes

wmemset.cpp style fix

93305b5

michaelrj-google merged commit 6cf53da into llvm:main May 29, 2025
15 of 16 checks passed

michaelrj-google mentioned this pull request May 29, 2025

[libc] Implement wmemset #141636

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svkeerthy pushed a commit that referenced this pull request May 29, 2025

[libc] Implemented wmemset and added tests (#141691)

a267962

Implemented and tests the wmemset function in libc.

google-yfyang pushed a commit to google-yfyang/llvm-project that referenced this pull request May 29, 2025

[libc] Implemented wmemset and added tests (llvm#141691)

437c1d9

Implemented and tests the wmemset function in libc.

sivan-shani pushed a commit to sivan-shani/llvm-project that referenced this pull request Jun 3, 2025

[libc] Implemented wmemset and added tests (llvm#141691)

82286d8

Implemented and tests the wmemset function in libc.

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	const wchar_t magic = INT32_MAX;
	const wchar_t magic = WCHAR_MAX;

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