[libc-commits] [libc] [libc] Implement pause (PR #225365)
Jeff Bailey via libc-commits
libc-commits at lists.llvm.org
Tue Sep 22 04:09:30 PDT 2026
https://github.com/kaladron created https://github.com/llvm/llvm-project/pull/225365
Add the linux_syscalls::pause wrapper using SYS_ppoll, along with the unistd pause entrypoint and unit test on Linux.
Assisted-by: Automated tooling, human reviewed.
>From 37e48c78c765edfc905d3061dbaf63abf5b7bb9b Mon Sep 17 00:00:00 2001
From: Jeff Bailey <jbailey at raspberryginger.com>
Date: Tue, 22 Sep 2026 12:07:22 +0100
Subject: [PATCH] [libc] Implement pause
Add the linux_syscalls::pause wrapper using SYS_ppoll, along with the
unistd pause entrypoint and unit test on Linux.
Assisted-by: Automated tooling, human reviewed.
---
libc/config/linux/aarch64/entrypoints.txt | 1 +
libc/config/linux/arm/entrypoints.txt | 1 +
libc/config/linux/riscv/entrypoints.txt | 1 +
libc/config/linux/x86_64/entrypoints.txt | 1 +
libc/include/unistd.yaml | 6 ++
.../linux/syscall_wrappers/CMakeLists.txt | 13 ++++
.../OSUtil/linux/syscall_wrappers/pause.h | 33 ++++++++++
libc/src/unistd/CMakeLists.txt | 7 ++
libc/src/unistd/linux/CMakeLists.txt | 13 ++++
libc/src/unistd/linux/pause.cpp | 32 +++++++++
libc/src/unistd/pause.h | 25 +++++++
libc/test/src/unistd/CMakeLists.txt | 21 ++++++
libc/test/src/unistd/pause_test.cpp | 65 +++++++++++++++++++
13 files changed, 219 insertions(+)
create mode 100644 libc/src/__support/OSUtil/linux/syscall_wrappers/pause.h
create mode 100644 libc/src/unistd/linux/pause.cpp
create mode 100644 libc/src/unistd/pause.h
create mode 100644 libc/test/src/unistd/pause_test.cpp
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index f55ac4b16cfd26..88521f41a4cabe 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -456,6 +456,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.unistd.lseek
libc.src.unistd.nice
libc.src.unistd.pathconf
+ libc.src.unistd.pause
libc.src.unistd.pipe
libc.src.unistd.pipe2
libc.src.unistd.pread
diff --git a/libc/config/linux/arm/entrypoints.txt b/libc/config/linux/arm/entrypoints.txt
index 1602255c6559cc..8d020a9ef40d42 100644
--- a/libc/config/linux/arm/entrypoints.txt
+++ b/libc/config/linux/arm/entrypoints.txt
@@ -270,6 +270,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.unistd.linkat
libc.src.unistd.lseek
libc.src.unistd.nice
+ libc.src.unistd.pause
libc.src.unistd.pipe
libc.src.unistd.pipe2
libc.src.unistd.read
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 921de1c649fb42..9f21c4c271ef21 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -481,6 +481,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.unistd.lseek
libc.src.unistd.nice
libc.src.unistd.pathconf
+ libc.src.unistd.pause
libc.src.unistd.pipe
libc.src.unistd.pipe2
libc.src.unistd.pread
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 165484987f16d7..1087e710542ec0 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -495,6 +495,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.unistd.lseek
libc.src.unistd.nice
libc.src.unistd.pathconf
+ libc.src.unistd.pause
libc.src.unistd.pipe
libc.src.unistd.pipe2
libc.src.unistd.pread
diff --git a/libc/include/unistd.yaml b/libc/include/unistd.yaml
index 890a4ae21f1919..1f3f064c50dd5c 100644
--- a/libc/include/unistd.yaml
+++ b/libc/include/unistd.yaml
@@ -417,6 +417,12 @@ functions:
arguments:
- type: const char *
- type: int
+ - name: pause
+ standards:
+ - posix
+ return_type: int
+ arguments:
+ - type: void
- name: pipe
standards:
- posix
diff --git a/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt b/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt
index f5f28f51f49f60..e4f34682abe583 100644
--- a/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt
+++ b/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt
@@ -1356,3 +1356,16 @@ add_header_library(
libc.src.__support.CPP.bit
libc.src.__support.error_or
)
+
+add_header_library(
+ pause
+ HDRS
+ pause.h
+ DEPENDS
+ libc.include.sys_syscall
+ libc.src.__support.common
+ libc.src.__support.error_or
+ libc.src.__support.macros.config
+ libc.src.__support.OSUtil.osutil
+)
+
diff --git a/libc/src/__support/OSUtil/linux/syscall_wrappers/pause.h b/libc/src/__support/OSUtil/linux/syscall_wrappers/pause.h
new file mode 100644
index 00000000000000..c5dcb01bb86ea8
--- /dev/null
+++ b/libc/src/__support/OSUtil/linux/syscall_wrappers/pause.h
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+/// Syscall wrapper for pause.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_PAUSE_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_PAUSE_H
+
+#include "src/__support/OSUtil/linux/syscall.h"
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h>
+
+namespace LIBC_NAMESPACE_DECL {
+namespace linux_syscalls {
+
+LIBC_INLINE ErrorOr<int> pause() {
+ return syscall_checked<int>(SYS_ppoll, nullptr, 0, nullptr, nullptr, 0);
+}
+
+} // namespace linux_syscalls
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_PAUSE_H
diff --git a/libc/src/unistd/CMakeLists.txt b/libc/src/unistd/CMakeLists.txt
index 97bae9a643f345..236488c8170f46 100644
--- a/libc/src/unistd/CMakeLists.txt
+++ b/libc/src/unistd/CMakeLists.txt
@@ -301,6 +301,13 @@ add_entrypoint_object(
.${LIBC_TARGET_OS}.pathconf
)
+add_entrypoint_object(
+ pause
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.pause
+)
+
add_entrypoint_object(
pipe
ALIAS
diff --git a/libc/src/unistd/linux/CMakeLists.txt b/libc/src/unistd/linux/CMakeLists.txt
index d4e03819612b92..75049bf2bd7c05 100644
--- a/libc/src/unistd/linux/CMakeLists.txt
+++ b/libc/src/unistd/linux/CMakeLists.txt
@@ -510,6 +510,19 @@ add_object_library(
libc.hdr.types.struct_statfs
)
+add_entrypoint_object(
+ pause
+ SRCS
+ pause.cpp
+ HDRS
+ ../pause.h
+ DEPENDS
+ libc.src.__support.OSUtil.linux.syscall_wrappers.pause
+ libc.src.__support.common
+ libc.src.__support.macros.config
+ libc.src.errno.errno
+)
+
add_entrypoint_object(
pipe
SRCS
diff --git a/libc/src/unistd/linux/pause.cpp b/libc/src/unistd/linux/pause.cpp
new file mode 100644
index 00000000000000..8ad6b121f57294
--- /dev/null
+++ b/libc/src/unistd/linux/pause.cpp
@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 pause.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/pause.h"
+
+#include "src/__support/OSUtil/linux/syscall_wrappers/pause.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, pause, ()) {
+ ErrorOr<int> ret = linux_syscalls::pause();
+ if (!ret) {
+ libc_errno = ret.error();
+ return -1;
+ }
+ return ret.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/unistd/pause.h b/libc/src/unistd/pause.h
new file mode 100644
index 00000000000000..23b1fc49fbebdd
--- /dev/null
+++ b/libc/src/unistd/pause.h
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 pause.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_UNISTD_PAUSE_H
+#define LLVM_LIBC_SRC_UNISTD_PAUSE_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int pause();
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_UNISTD_PAUSE_H
diff --git a/libc/test/src/unistd/CMakeLists.txt b/libc/test/src/unistd/CMakeLists.txt
index 17960278bd3f75..2e44a1c2ddc90d 100644
--- a/libc/test/src/unistd/CMakeLists.txt
+++ b/libc/test/src/unistd/CMakeLists.txt
@@ -873,6 +873,27 @@ add_libc_test(
libc.test.UnitTest.ErrnoSetterMatcher
)
+add_libc_test(
+ pause_test
+ SUITE
+ libc_unistd_unittests
+ SRCS
+ pause_test.cpp
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.signal_macros
+ libc.hdr.sys_time_macros
+ libc.hdr.types.struct_itimerval
+ libc.hdr.types.struct_sigaction
+ libc.src.__support.CPP.scope
+ libc.src.signal.sigaction
+ libc.src.signal.sigemptyset
+ libc.src.sys.time.setitimer
+ libc.src.unistd.pause
+ libc.test.UnitTest.ErrnoCheckingTest
+ libc.test.UnitTest.ErrnoSetterMatcher
+)
+
add_libc_test(
getopt_test
SUITE
diff --git a/libc/test/src/unistd/pause_test.cpp b/libc/test/src/unistd/pause_test.cpp
new file mode 100644
index 00000000000000..b1466a0b5c72fc
--- /dev/null
+++ b/libc/test/src/unistd/pause_test.cpp
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+/// Unittests for pause.
+///
+//===----------------------------------------------------------------------===//
+
+#include "hdr/errno_macros.h"
+#include "hdr/signal_macros.h"
+#include "hdr/sys_time_macros.h"
+#include "hdr/types/struct_itimerval.h"
+#include "hdr/types/struct_sigaction.h"
+#include "src/__support/CPP/scope.h"
+#include "src/signal/sigaction.h"
+#include "src/signal/sigemptyset.h"
+#include "src/sys/time/setitimer.h"
+#include "src/unistd/pause.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+using LlvmLibcPauseTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+static volatile bool alarm_fired = false;
+
+extern "C" void pause_sigalrm_handler(int) { alarm_fired = true; }
+
+TEST_F(LlvmLibcPauseTest, InterruptedBySignal) {
+ alarm_fired = false;
+
+ struct sigaction sa = {};
+ sa.sa_handler = pause_sigalrm_handler;
+ ASSERT_THAT(LIBC_NAMESPACE::sigemptyset(&sa.sa_mask), Succeeds(0));
+ sa.sa_flags = 0;
+
+ struct sigaction old_sa = {};
+ ASSERT_THAT(LIBC_NAMESPACE::sigaction(SIGALRM, &sa, &old_sa), Succeeds(0));
+ auto restore_sigaction = LIBC_NAMESPACE::cpp::scope_exit(
+ [&] { LIBC_NAMESPACE::sigaction(SIGALRM, &old_sa, nullptr); });
+
+ // Use a short repeating interval timer so that even if a signal arrives
+ // before pause() blocks, the subsequent tick wakes pause() immediately.
+ struct itimerval timer = {};
+ timer.it_value.tv_sec = 0;
+ timer.it_value.tv_usec = 10000;
+ timer.it_interval.tv_sec = 0;
+ timer.it_interval.tv_usec = 10000;
+
+ struct itimerval old_timer = {};
+ ASSERT_THAT(LIBC_NAMESPACE::setitimer(ITIMER_REAL, &timer, &old_timer),
+ Succeeds(0));
+ auto restore_timer = LIBC_NAMESPACE::cpp::scope_exit(
+ [&] { LIBC_NAMESPACE::setitimer(ITIMER_REAL, &old_timer, nullptr); });
+
+ EXPECT_THAT(LIBC_NAMESPACE::pause(), Fails(EINTR));
+ EXPECT_TRUE(alarm_fired);
+}
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