Export of internal Abseil changes

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a85860e450815776c8753f34348f41ab0e918d36 by Gennadiy Rozental <rogeeff@google.com>:

Rename ComamndLineFlag's interface SetFromString as ParseFrom.

This is the name approved by C++ API review.

PiperOrigin-RevId: 301543521

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28f31bae2a136854fd89f0a32f281d12a40f702c by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 301524919

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a68da3d6fbbca4c5f41a20e99ed72bb1c5dd1165 by Abseil Team <absl-team@google.com>:

Introduce absl::base_internal::StrError, a portability wrapper around the various thread-safe alternatives to C89's strerror.

PiperOrigin-RevId: 301513962

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92ccac3b6eb18cb41cddedbfdab53b9ad481505d by Andy Getzendanner <durandal@google.com>:

Introduce absl::base_internal::StrError, a portability wrapper around the various thread-safe alternatives to C89's strerror.

PiperOrigin-RevId: 301493389

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8e196def47c250941202840d6a1de686d681cd3e by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 301363394

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dd1dcffa6c47675ba4d198730a301bd408142298 by Gennadiy Rozental <rogeeff@google.com>:

Add validation for size of void* to match the size of free function pointer.

PiperOrigin-RevId: 301341331
GitOrigin-RevId: a85860e450815776c8753f34348f41ab0e918d36
Change-Id: I27c9d1365d3c9b4328d1587ab3ac38e2d09a6ec2

5 files changed, 240 insertions, 1 deletions

diff --git a/absl/base/internal/errno_saver_test.cc b/absl/base/internal/errno_saver_test.cc
index b845e2dd..e9b742c5 100644
--- a/absl/base/internal/errno_saver_test.cc
+++ b/absl/base/internal/errno_saver_test.cc
@@ -18,6 +18,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/base/internal/strerror.h"
 
 namespace {
 using ::testing::Eq;
@@ -26,7 +27,7 @@ struct ErrnoPrinter {
   int no;
 };
 std::ostream &operator<<(std::ostream &os, ErrnoPrinter ep) {
-  return os << strerror(ep.no) << " [" << ep.no << "]";
+  return os << absl::base_internal::StrError(ep.no) << " [" << ep.no << "]";
 }
 bool operator==(ErrnoPrinter one, ErrnoPrinter two) { return one.no == two.no; }
 
diff --git a/absl/base/internal/strerror.cc b/absl/base/internal/strerror.cc
new file mode 100644
index 00000000..af181513
--- /dev/null
+++ b/absl/base/internal/strerror.cc
@@ -0,0 +1,75 @@
+// Copyright 2020 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/strerror.h"
+
+#include <cerrno>
+#include <cstddef>
+#include <cstdio>
+#include <cstring>
+#include <string>
+#include <type_traits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/errno_saver.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace base_internal {
+namespace {
+const char* StrErrorAdaptor(int errnum, char* buf, size_t buflen) {
+#if defined(_WIN32)
+  int rc = strerror_s(buf, buflen, errnum);
+  buf[buflen - 1] = '\0';  // guarantee NUL termination
+  if (rc == 0 && strncmp(buf, "Unknown error", buflen) == 0) *buf = '\0';
+  return buf;
+#else
+#if defined(__GLIBC__) || defined(__APPLE__)
+  // Use the BSD sys_errlist API provided by GNU glibc and others to
+  // avoid any need to copy the message into the local buffer first.
+  if (0 <= errnum && errnum < sys_nerr) {
+    if (const char* p = sys_errlist[errnum]) {
+      return p;
+    }
+  }
+#endif
+  // The type of `ret` is platform-specific; both of these branches must compile
+  // either way but only one will execute on any given platform:
+  auto ret = strerror_r(errnum, buf, buflen);
+  if (std::is_same<decltype(ret), int>::value) {
+    // XSI `strerror_r`; `ret` is `int`:
+    if (ret) *buf = '\0';
+    return buf;
+  } else {
+    // GNU `strerror_r`; `ret` is `char *`:
+    return reinterpret_cast<const char*>(ret);
+  }
+#endif
+}
+}  // namespace
+
+std::string StrError(int errnum) {
+  absl::base_internal::ErrnoSaver errno_saver;
+  char buf[100];
+  const char* str = StrErrorAdaptor(errnum, buf, sizeof buf);
+  if (*str == '\0') {
+    snprintf(buf, sizeof buf, "Unknown error %d", errnum);
+    str = buf;
+  }
+  return str;
+}
+
+}  // namespace base_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/base/internal/strerror.h b/absl/base/internal/strerror.h
new file mode 100644
index 00000000..35009736
--- /dev/null
+++ b/absl/base/internal/strerror.h
@@ -0,0 +1,39 @@
+// Copyright 2020 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_STRERROR_H_
+#define ABSL_BASE_INTERNAL_STRERROR_H_
+
+#include <string>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace base_internal {
+
+// A portable and thread-safe alternative to C89's `strerror`.
+//
+// The C89 specification of `strerror` is not suitable for use in a
+// multi-threaded application as the returned string may be changed by calls to
+// `strerror` from another thread.  The many non-stdlib alternatives differ
+// enough in their names, availability, and semantics to justify this wrapper
+// around them.  `errno` will not be modified by a call to `absl::StrError`.
+std::string StrError(int errnum);
+
+}  // namespace base_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_BASE_INTERNAL_STRERROR_H_
diff --git a/absl/base/internal/strerror_benchmark.cc b/absl/base/internal/strerror_benchmark.cc
new file mode 100644
index 00000000..d8ca86b9
--- /dev/null
+++ b/absl/base/internal/strerror_benchmark.cc
@@ -0,0 +1,38 @@
+// Copyright 2020 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 <cerrno>
+#include <cstdio>
+#include <string>
+
+#include "absl/base/internal/strerror.h"
+#include "benchmark/benchmark.h"
+
+namespace {
+#if defined(__GLIBC__) || defined(__APPLE__)
+void BM_SysErrList(benchmark::State& state) {
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(std::string(sys_errlist[ERANGE]));
+  }
+}
+BENCHMARK(BM_SysErrList);
+#endif
+
+void BM_AbslStrError(benchmark::State& state) {
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(absl::base_internal::StrError(ERANGE));
+  }
+}
+BENCHMARK(BM_AbslStrError);
+}  // namespace
diff --git a/absl/base/internal/strerror_test.cc b/absl/base/internal/strerror_test.cc
new file mode 100644
index 00000000..a53da97f
--- /dev/null
+++ b/absl/base/internal/strerror_test.cc
@@ -0,0 +1,86 @@
+// Copyright 2020 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/strerror.h"
+
+#include <atomic>
+#include <cerrno>
+#include <cstdio>
+#include <cstring>
+#include <string>
+#include <thread>  // NOLINT(build/c++11)
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/match.h"
+
+namespace {
+using ::testing::AnyOf;
+using ::testing::Eq;
+
+TEST(StrErrorTest, ValidErrorCode) {
+  errno = ERANGE;
+  EXPECT_THAT(absl::base_internal::StrError(EDOM), Eq(strerror(EDOM)));
+  EXPECT_THAT(errno, Eq(ERANGE));
+}
+
+TEST(StrErrorTest, InvalidErrorCode) {
+  errno = ERANGE;
+  EXPECT_THAT(absl::base_internal::StrError(-1),
+              AnyOf(Eq("No error information"), Eq("Unknown error -1")));
+  EXPECT_THAT(errno, Eq(ERANGE));
+}
+
+TEST(StrErrorTest, MultipleThreads) {
+  // In this test, we will start up 2 threads and have each one call
+  // StrError 1000 times, each time with a different errnum.  We
+  // expect that StrError(errnum) will return a string equal to the
+  // one returned by strerror(errnum), if the code is known.  Since
+  // strerror is known to be thread-hostile, collect all the expected
+  // strings up front.
+  const int kNumCodes = 1000;
+  std::vector<std::string> expected_strings(kNumCodes);
+  for (int i = 0; i < kNumCodes; ++i) {
+    expected_strings[i] = strerror(i);
+  }
+
+  std::atomic_int counter(0);
+  auto thread_fun = [&]() {
+    for (int i = 0; i < kNumCodes; ++i) {
+      ++counter;
+      errno = ERANGE;
+      const std::string value = absl::base_internal::StrError(i);
+      // Only the GNU implementation is guaranteed to provide the
+      // string "Unknown error nnn". POSIX doesn't say anything.
+      if (!absl::StartsWith(value, "Unknown error ")) {
+        EXPECT_THAT(absl::base_internal::StrError(i), Eq(expected_strings[i]));
+      }
+      EXPECT_THAT(errno, Eq(ERANGE));
+    }
+  };
+
+  const int kNumThreads = 100;
+  std::vector<std::thread> threads;
+  for (int i = 0; i < kNumThreads; ++i) {
+    threads.push_back(std::thread(thread_fun));
+  }
+  for (auto& thread : threads) {
+    thread.join();
+  }
+
+  EXPECT_THAT(counter, Eq(kNumThreads * kNumCodes));
+}
+
+}  // namespace