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-rw-r--r--absl/base/internal/errno_saver.h43
-rw-r--r--absl/base/internal/errno_saver_test.cc44
-rw-r--r--absl/base/internal/spinlock_linux.inc5
-rw-r--r--absl/base/internal/spinlock_posix.inc6
4 files changed, 92 insertions, 6 deletions
diff --git a/absl/base/internal/errno_saver.h b/absl/base/internal/errno_saver.h
new file mode 100644
index 00000000..251de510
--- /dev/null
+++ b/absl/base/internal/errno_saver.h
@@ -0,0 +1,43 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_BASE_INTERNAL_ERRNO_SAVER_H_
+#define ABSL_BASE_INTERNAL_ERRNO_SAVER_H_
+
+#include <cerrno>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace base_internal {
+
+// `ErrnoSaver` captures the value of `errno` upon construction and restores it
+// upon deletion. It is used in low-level code and must be super fast. Do not
+// add instrumentation, even in debug modes.
+class ErrnoSaver {
+ public:
+ ErrnoSaver() : saved_errno_(errno) {}
+ ~ErrnoSaver() { errno = saved_errno_; }
+ int operator()() const { return saved_errno_; }
+
+ private:
+ const int saved_errno_;
+};
+
+} // namespace base_internal
+ABSL_NAMESPACE_END
+} // namespace absl
+
+#endif // ABSL_BASE_INTERNAL_ERRNO_SAVER_H_
diff --git a/absl/base/internal/errno_saver_test.cc b/absl/base/internal/errno_saver_test.cc
new file mode 100644
index 00000000..b845e2dd
--- /dev/null
+++ b/absl/base/internal/errno_saver_test.cc
@@ -0,0 +1,44 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/base/internal/errno_saver.h"
+
+#include <cerrno>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace {
+using ::testing::Eq;
+
+struct ErrnoPrinter {
+ int no;
+};
+std::ostream &operator<<(std::ostream &os, ErrnoPrinter ep) {
+ return os << strerror(ep.no) << " [" << ep.no << "]";
+}
+bool operator==(ErrnoPrinter one, ErrnoPrinter two) { return one.no == two.no; }
+
+TEST(ErrnoSaverTest, Works) {
+ errno = EDOM;
+ {
+ absl::base_internal::ErrnoSaver errno_saver;
+ EXPECT_THAT(ErrnoPrinter{errno}, Eq(ErrnoPrinter{EDOM}));
+ errno = ERANGE;
+ EXPECT_THAT(ErrnoPrinter{errno}, Eq(ErrnoPrinter{ERANGE}));
+ EXPECT_THAT(ErrnoPrinter{errno_saver()}, Eq(ErrnoPrinter{EDOM}));
+ }
+ EXPECT_THAT(ErrnoPrinter{errno}, Eq(ErrnoPrinter{EDOM}));
+}
+} // namespace
diff --git a/absl/base/internal/spinlock_linux.inc b/absl/base/internal/spinlock_linux.inc
index 28e29d19..323edd62 100644
--- a/absl/base/internal/spinlock_linux.inc
+++ b/absl/base/internal/spinlock_linux.inc
@@ -19,12 +19,12 @@
#include <unistd.h>
#include <atomic>
-#include <cerrno>
#include <climits>
#include <cstdint>
#include <ctime>
#include "absl/base/attributes.h"
+#include "absl/base/internal/errno_saver.h"
// The SpinLock lockword is `std::atomic<uint32_t>`. Here we assert that
// `std::atomic<uint32_t>` is bitwise equivalent of the `int` expected
@@ -51,12 +51,11 @@ extern "C" {
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockDelay(
std::atomic<uint32_t> *w, uint32_t value, int loop,
absl::base_internal::SchedulingMode) {
- int save_errno = errno;
+ absl::base_internal::ErrnoSaver errno_saver;
struct timespec tm;
tm.tv_sec = 0;
tm.tv_nsec = absl::base_internal::SpinLockSuggestedDelayNS(loop);
syscall(SYS_futex, w, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, value, &tm);
- errno = save_errno;
}
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockWake(std::atomic<uint32_t> *w,
diff --git a/absl/base/internal/spinlock_posix.inc b/absl/base/internal/spinlock_posix.inc
index f025b5f8..fcd21b15 100644
--- a/absl/base/internal/spinlock_posix.inc
+++ b/absl/base/internal/spinlock_posix.inc
@@ -15,10 +15,11 @@
// This file is a Posix-specific part of spinlock_wait.cc
#include <sched.h>
+
#include <atomic>
#include <ctime>
-#include <cerrno>
+#include "absl/base/internal/errno_saver.h"
#include "absl/base/internal/scheduling_mode.h"
#include "absl/base/port.h"
@@ -27,7 +28,7 @@ extern "C" {
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockDelay(
std::atomic<uint32_t>* /* lock_word */, uint32_t /* value */, int loop,
absl::base_internal::SchedulingMode /* mode */) {
- int save_errno = errno;
+ absl::base_internal::ErrnoSaver errno_saver;
if (loop == 0) {
} else if (loop == 1) {
sched_yield();
@@ -37,7 +38,6 @@ ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockDelay(
tm.tv_nsec = absl::base_internal::SpinLockSuggestedDelayNS(loop);
nanosleep(&tm, nullptr);
}
- errno = save_errno;
}
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockWake(