[libc-commits] [libc] [libc] Implement mkfifoat in sys/stat (PR #224628)
Aman Maurya via libc-commits
libc-commits at lists.llvm.org
Fri Sep 18 06:10:24 PDT 2026
https://github.com/amanmaurya92 created https://github.com/llvm/llvm-project/pull/224628
### Summary
Implement the standard POSIX.1-2008 function `mkfifoat` in `<sys/stat.h>`.
Fixes #224587
### Changes
- Added `mkfifoat` function specification to `libc/include/sys/stat.yaml`.
- Added internal header `libc/src/sys/stat/mkfifoat.h`.
- Implemented `mkfifoat` in `libc/src/sys/stat/linux/mkfifoat.cpp` using the existing `linux_syscalls::mknodat`.
- Registered `mkfifoat` entrypoint in `libc/src/sys/stat/CMakeLists.txt` and `libc/src/sys/stat/linux/CMakeLists.txt`.
- Added entrypoint across Linux targets (`x86_64`, `aarch64`, `riscv`).
- Added hermetic unit tests in `libc/test/src/sys/stat/mkfifoat_test.cpp` using `cpp::scope_exit` cleanup and C++ `static_cast<mode_t>`.
### Testing
- Built and passed hermetic unit test `libc.test.src.sys.stat.mkfifoat_test` (4/4 tests passed).
- Verified sibling tests (`mkfifo_test`, `fstat_test`).
- Ran `generate-libc-headers` and verified generated `sys/stat.h`.
- Verified `docgen.py sys/stat.h` output marks `mkfifoat` as implemented.
- Ran `clang-format` on all touched C++ files.
>From 42d04e8354d8418d4a3e059e210c287709b631e5 Mon Sep 17 00:00:00 2001
From: amanmaurya92 <amanmaurya9209 at gmail.com>
Date: Fri, 18 Sep 2026 16:13:15 +0530
Subject: [PATCH] [libc] Implement mkfifoat in sys/stat
Implement the standard POSIX.1-2008 function mkfifoat in <sys/stat.h>.
Fixes #224587
Assisted by Antigravity and Gemini, reviewed by amanmaurya92.
---
libc/config/linux/aarch64/entrypoints.txt | 1 +
libc/config/linux/riscv/entrypoints.txt | 1 +
libc/config/linux/x86_64/entrypoints.txt | 1 +
libc/include/sys/stat.yaml | 6 ++
libc/src/sys/stat/CMakeLists.txt | 7 ++
libc/src/sys/stat/linux/CMakeLists.txt | 14 ++++
libc/src/sys/stat/linux/mkfifoat.cpp | 35 ++++++++++
libc/src/sys/stat/mkfifoat.h | 26 +++++++
libc/test/src/sys/stat/CMakeLists.txt | 24 +++++++
libc/test/src/sys/stat/mkfifoat_test.cpp | 83 +++++++++++++++++++++++
10 files changed, 198 insertions(+)
create mode 100644 libc/src/sys/stat/linux/mkfifoat.cpp
create mode 100644 libc/src/sys/stat/mkfifoat.h
create mode 100644 libc/test/src/sys/stat/mkfifoat_test.cpp
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 1a05ed55365b4..9c26f852c176a 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -355,6 +355,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sys.stat.mkdir
libc.src.sys.stat.mkdirat
libc.src.sys.stat.mkfifo
+ libc.src.sys.stat.mkfifoat
libc.src.sys.stat.stat
libc.src.sys.stat.umask
libc.src.sys.stat.utimensat
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index ba3600966fabf..949d253ca210b 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -386,6 +386,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sys.stat.mkdir
libc.src.sys.stat.mkdirat
libc.src.sys.stat.mkfifo
+ libc.src.sys.stat.mkfifoat
libc.src.sys.stat.stat
libc.src.sys.stat.umask
libc.src.sys.stat.utimensat
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index a32e83236e277..9eae3cd1dd7cc 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -391,6 +391,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sys.stat.mkdir
libc.src.sys.stat.mkdirat
libc.src.sys.stat.mkfifo
+ libc.src.sys.stat.mkfifoat
libc.src.sys.stat.stat
libc.src.sys.stat.umask
libc.src.sys.stat.utimensat
diff --git a/libc/include/sys/stat.yaml b/libc/include/sys/stat.yaml
index 3c75ce3d796cb..2c85429cfef17 100644
--- a/libc/include/sys/stat.yaml
+++ b/libc/include/sys/stat.yaml
@@ -63,6 +63,12 @@ functions:
arguments:
- type: const char *
- type: mode_t
+ - name: mkfifoat
+ return_type: int
+ arguments:
+ - type: int
+ - type: const char *
+ - type: mode_t
- name: stat
return_type: int
arguments:
diff --git a/libc/src/sys/stat/CMakeLists.txt b/libc/src/sys/stat/CMakeLists.txt
index ae1a3f76078f1..8481434bc2847 100644
--- a/libc/src/sys/stat/CMakeLists.txt
+++ b/libc/src/sys/stat/CMakeLists.txt
@@ -58,6 +58,13 @@ add_entrypoint_object(
.${LIBC_TARGET_OS}.mkfifo
)
+add_entrypoint_object(
+ mkfifoat
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.mkfifoat
+)
+
add_entrypoint_object(
stat
ALIAS
diff --git a/libc/src/sys/stat/linux/CMakeLists.txt b/libc/src/sys/stat/linux/CMakeLists.txt
index b087fc927459c..f53189bb0c5cc 100644
--- a/libc/src/sys/stat/linux/CMakeLists.txt
+++ b/libc/src/sys/stat/linux/CMakeLists.txt
@@ -74,6 +74,20 @@ add_entrypoint_object(
libc.src.errno.errno
)
+add_entrypoint_object(
+ mkfifoat
+ SRCS
+ mkfifoat.cpp
+ HDRS
+ ../mkfifoat.h
+ DEPENDS
+ libc.hdr.fcntl_macros
+ libc.hdr.sys_stat_macros
+ libc.hdr.types.mode_t
+ libc.src.__support.OSUtil.linux.syscall_wrappers.mknodat
+ libc.src.errno.errno
+)
+
add_entrypoint_object(
stat
SRCS
diff --git a/libc/src/sys/stat/linux/mkfifoat.cpp b/libc/src/sys/stat/linux/mkfifoat.cpp
new file mode 100644
index 0000000000000..68363c177169f
--- /dev/null
+++ b/libc/src/sys/stat/linux/mkfifoat.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Linux implementation of mkfifoat.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/stat/mkfifoat.h"
+
+#include "hdr/fcntl_macros.h"
+#include "hdr/sys_stat_macros.h"
+#include "hdr/types/mode_t.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/mknodat.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, mkfifoat, (int dirfd, const char *path, mode_t mode)) {
+ auto result = linux_syscalls::mknodat(dirfd, path, mode | S_IFIFO, 0);
+ if (!result) {
+ libc_errno = result.error();
+ return -1;
+ }
+ return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/stat/mkfifoat.h b/libc/src/sys/stat/mkfifoat.h
new file mode 100644
index 0000000000000..f1f2f57e6b8a8
--- /dev/null
+++ b/libc/src/sys/stat/mkfifoat.h
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation header for mkfifoat.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_STAT_MKFIFOAT_H
+#define LLVM_LIBC_SRC_SYS_STAT_MKFIFOAT_H
+
+#include "hdr/types/mode_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int mkfifoat(int dirfd, const char *path, mode_t mode);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_STAT_MKFIFOAT_H
diff --git a/libc/test/src/sys/stat/CMakeLists.txt b/libc/test/src/sys/stat/CMakeLists.txt
index 775348f8c18fa..3c9842d0f7f5a 100644
--- a/libc/test/src/sys/stat/CMakeLists.txt
+++ b/libc/test/src/sys/stat/CMakeLists.txt
@@ -96,6 +96,30 @@ add_libc_test(
libc.test.UnitTest.ErrnoSetterMatcher
)
+add_libc_test(
+ mkfifoat_test
+ SUITE
+ libc_sys_stat_unittests
+ SRCS
+ mkfifoat_test.cpp
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.fcntl_macros
+ libc.hdr.sys_stat_macros
+ libc.hdr.types.mode_t
+ libc.hdr.types.struct_stat
+ libc.src.__support.CPP.scope
+ libc.src.errno.errno
+ libc.src.fcntl.open
+ libc.src.sys.stat.mkfifoat
+ libc.src.sys.stat.stat
+ libc.src.sys.stat.umask
+ libc.src.unistd.close
+ libc.src.unistd.unlink
+ libc.test.UnitTest.ErrnoCheckingTest
+ libc.test.UnitTest.ErrnoSetterMatcher
+)
+
add_libc_test(
stat_test
SUITE
diff --git a/libc/test/src/sys/stat/mkfifoat_test.cpp b/libc/test/src/sys/stat/mkfifoat_test.cpp
new file mode 100644
index 0000000000000..bacfc842d0df0
--- /dev/null
+++ b/libc/test/src/sys/stat/mkfifoat_test.cpp
@@ -0,0 +1,83 @@
+//===-- Unittests for mkfifoat --------------------------------------------===//
+//
+// 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/fcntl_macros.h"
+#include "hdr/sys_stat_macros.h"
+#include "hdr/types/mode_t.h"
+#include "hdr/types/struct_stat.h"
+#include "src/__support/CPP/scope.h"
+#include "src/fcntl/open.h"
+#include "src/sys/stat/mkfifoat.h"
+#include "src/sys/stat/stat.h"
+#include "src/sys/stat/umask.h"
+#include "src/unistd/close.h"
+#include "src/unistd/unlink.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+using LlvmLibcMkfifoatTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcMkfifoatTest, CreateAndRemoveWithAtFdcwd) {
+ constexpr const char *TEST_FIFO = "testdata/mkfifoat.testfifo";
+ constexpr mode_t FIFO_MODE = S_IRUSR | S_IWUSR;
+
+ mode_t old_mask = LIBC_NAMESPACE::umask(0);
+ ASSERT_THAT(LIBC_NAMESPACE::mkfifoat(AT_FDCWD, TEST_FIFO, FIFO_MODE),
+ Succeeds(0));
+ LIBC_NAMESPACE::umask(old_mask);
+
+ LIBC_NAMESPACE::cpp::scope_exit cleanup(
+ [&] { EXPECT_THAT(LIBC_NAMESPACE::unlink(TEST_FIFO), Succeeds(0)); });
+
+ struct stat statbuf;
+ ASSERT_THAT(LIBC_NAMESPACE::stat(TEST_FIFO, &statbuf), Succeeds(0));
+ ASSERT_TRUE(S_ISFIFO(statbuf.st_mode));
+ ASSERT_EQ(statbuf.st_mode & 07777, static_cast<mode_t>(FIFO_MODE));
+}
+
+TEST_F(LlvmLibcMkfifoatTest, CreateAndRemoveWithDirFd) {
+ constexpr const char *TEST_DIR = "testdata";
+ constexpr const char *TEST_FIFO_BASENAME = "mkfifoat_dir.testfifo";
+ constexpr const char *TEST_FIFO_PATH = "testdata/mkfifoat_dir.testfifo";
+ constexpr mode_t FIFO_MODE = S_IRUSR | S_IWUSR;
+
+ int dirfd = LIBC_NAMESPACE::open(TEST_DIR, O_DIRECTORY);
+ ASSERT_GT(dirfd, 0);
+ ASSERT_ERRNO_SUCCESS();
+ LIBC_NAMESPACE::cpp::scope_exit cleanup_dir(
+ [&] { EXPECT_THAT(LIBC_NAMESPACE::close(dirfd), Succeeds(0)); });
+
+ mode_t old_mask = LIBC_NAMESPACE::umask(0);
+ ASSERT_THAT(LIBC_NAMESPACE::mkfifoat(dirfd, TEST_FIFO_BASENAME, FIFO_MODE),
+ Succeeds(0));
+ LIBC_NAMESPACE::umask(old_mask);
+
+ LIBC_NAMESPACE::cpp::scope_exit cleanup_fifo([&] {
+ EXPECT_THAT(LIBC_NAMESPACE::unlink(TEST_FIFO_PATH), Succeeds(0));
+ });
+
+ struct stat statbuf;
+ ASSERT_THAT(LIBC_NAMESPACE::stat(TEST_FIFO_PATH, &statbuf), Succeeds(0));
+ ASSERT_TRUE(S_ISFIFO(statbuf.st_mode));
+ ASSERT_EQ(statbuf.st_mode & 07777, static_cast<mode_t>(FIFO_MODE));
+}
+
+TEST_F(LlvmLibcMkfifoatTest, BadDirFd) {
+ ASSERT_THAT(LIBC_NAMESPACE::mkfifoat(-1, "some-file", S_IRUSR | S_IWUSR),
+ Fails(EBADF));
+}
+
+TEST_F(LlvmLibcMkfifoatTest, NonExistentPath) {
+ ASSERT_THAT(LIBC_NAMESPACE::mkfifoat(
+ AT_FDCWD, "testdata/non-existent-dir/mkfifoat.testfifo",
+ S_IRUSR | S_IWUSR),
+ Fails(ENOENT));
+}
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