http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/call_once_test.cc
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diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/call_once_test.cc 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/call_once_test.cc
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+// 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
+//
+//      http://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/call_once.h"
+
+#include <thread>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+namespace {
+
+absl::once_flag once;
+Mutex counters_mu;
+
+int running_thread_count GUARDED_BY(counters_mu) = 0;
+int call_once_invoke_count GUARDED_BY(counters_mu) = 0;
+int call_once_finished_count GUARDED_BY(counters_mu) = 0;
+int call_once_return_count GUARDED_BY(counters_mu) = 0;
+bool done_blocking GUARDED_BY(counters_mu) = false;
+
+// Function to be called from absl::call_once.  Waits for a notification.
+void WaitAndIncrement() {
+  counters_mu.Lock();
+  ++call_once_invoke_count;
+  counters_mu.Unlock();
+
+  counters_mu.LockWhen(Condition(&done_blocking));
+  ++call_once_finished_count;
+  counters_mu.Unlock();
+}
+
+void ThreadBody() {
+  counters_mu.Lock();
+  ++running_thread_count;
+  counters_mu.Unlock();
+
+  absl::call_once(once, WaitAndIncrement);
+
+  counters_mu.Lock();
+  ++call_once_return_count;
+  counters_mu.Unlock();
+}
+
+// Returns true if all threads are set up for the test.
+bool ThreadsAreSetup(void*) EXCLUSIVE_LOCKS_REQUIRED(counters_mu) {
+  // All ten threads must be running, and WaitAndIncrement should be blocked.
+  return running_thread_count == 10 && call_once_invoke_count == 1;
+}
+
+TEST(CallOnceTest, ExecutionCount) {
+  std::vector<std::thread> threads;
+
+  // Start 10 threads all calling call_once on the same once_flag.
+  for (int i = 0; i < 10; ++i) {
+    threads.emplace_back(ThreadBody);
+  }
+
+
+  // Wait until all ten threads have started, and WaitAndIncrement has been
+  // invoked.
+  counters_mu.LockWhen(Condition(ThreadsAreSetup, nullptr));
+
+  // WaitAndIncrement should have been invoked by exactly one call_once()
+  // instance.  That thread should be blocking on a notification, and all other
+  // call_once instances should be blocking as well.
+  EXPECT_EQ(call_once_invoke_count, 1);
+  EXPECT_EQ(call_once_finished_count, 0);
+  EXPECT_EQ(call_once_return_count, 0);
+
+  // Allow WaitAndIncrement to finish executing.  Once it does, the other
+  // call_once waiters will be unblocked.
+  done_blocking = true;
+  counters_mu.Unlock();
+
+  for (std::thread& thread : threads) {
+    thread.join();
+  }
+
+  counters_mu.Lock();
+  EXPECT_EQ(call_once_invoke_count, 1);
+  EXPECT_EQ(call_once_finished_count, 1);
+  EXPECT_EQ(call_once_return_count, 10);
+  counters_mu.Unlock();
+}
+
+}  // namespace
+}  // namespace absl

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/casts.h
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diff --git a/libraries/ostrich/backend/3rdparty/abseil/absl/base/casts.h 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/casts.h
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+//
+// 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
+//
+//      http://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.
+//
+// 
-----------------------------------------------------------------------------
+// File: casts.h
+// 
-----------------------------------------------------------------------------
+//
+// This header file defines casting templates to fit use cases not covered by
+// the standard casts provided in the C++ standard. As with all cast 
operations,
+// use these with caution and only if alternatives do not exist.
+
+#ifndef ABSL_BASE_CASTS_H_
+#define ABSL_BASE_CASTS_H_
+
+#include <cstring>
+#include <type_traits>
+
+#include "absl/base/internal/identity.h"
+
+namespace absl {
+
+// implicit_cast()
+//
+// Performs an implicit conversion between types following the language
+// rules for implicit conversion; if an implicit conversion is otherwise
+// allowed by the language in the given context, this function performs such an
+// implicit conversion.
+//
+// Example:
+//
+//   // If the context allows implicit conversion:
+//   From from;
+//   To to = from;
+//
+//   // Such code can be replaced by:
+//   implicit_cast<To>(from);
+//
+// An `implicit_cast()` may also be used to annotate numeric type conversions
+// that, although safe, may produce compiler warnings (such as `long` to 
`int`).
+// Additionally, an `implicit_cast()` is also useful within return statements 
to
+// indicate a specific implicit conversion is being undertaken.
+//
+// Example:
+//
+//   return implicit_cast<double>(size_in_bytes) / capacity_;
+//
+// Annotating code with `implicit_cast()` allows you to explicitly select
+// particular overloads and template instantiations, while providing a safer
+// cast than `reinterpret_cast()` or `static_cast()`.
+//
+// Additionally, an `implicit_cast()` can be used to allow upcasting within a
+// type hierarchy where incorrect use of `static_cast()` could accidentally
+// allow downcasting.
+//
+// Finally, an `implicit_cast()` can be used to perform implicit conversions
+// from unrelated types that otherwise couldn't be implicitly cast directly;
+// C++ will normally only implicitly cast "one step" in such conversions.
+//
+// That is, if C is a type which can be implicitly converted to B, with B being
+// a type that can be implicitly converted to A, an `implicit_cast()` can be
+// used to convert C to B (which the compiler can then implicitly convert to A
+// using language rules).
+//
+// Example:
+//
+//   // Assume an object C is convertible to B, which is implicitly convertible
+//   // to A
+//   A a = implicit_cast<B>(C);
+//
+// Such implicit cast chaining may be useful within template logic.
+template <typename To>
+inline To implicit_cast(typename absl::internal::identity_t<To> to) {
+  return to;
+}
+
+// bit_cast()
+//
+// Performs a bitwise cast on a type without changing the underlying bit
+// representation of that type's value. The two types must be of the same size
+// and both types must be trivially copyable. As with most casts, use with
+// caution. A `bit_cast()` might be needed when you need to temporarily treat a
+// type as some other type, such as in the following cases:
+//
+//    * Serialization (casting temporarily to `char *` for those purposes is
+//      always allowed by the C++ standard)
+//    * Managing the individual bits of a type within mathematical operations
+//      that are not normally accessible through that type
+//    * Casting non-pointer types to pointer types (casting the other way is
+//      allowed by `reinterpret_cast()` but round-trips cannot occur the other
+//      way).
+//
+// Example:
+//
+//   float f = 3.14159265358979;
+//   int i = bit_cast<int32_t>(f);
+//   // i = 0x40490fdb
+//
+// Casting non-pointer types to pointer types and then dereferencing them
+// traditionally produces undefined behavior.
+//
+// Example:
+//
+//   // WRONG
+//   float f = 3.14159265358979;            // WRONG
+//   int i = * reinterpret_cast<int*>(&f);  // WRONG
+//
+// The address-casting method produces undefined behavior according to the ISO
+// C++ specification section [basic.lval]. Roughly, this section says: if an
+// object in memory has one type, and a program accesses it with a different
+// type, the result is undefined behavior for most values of "different type".
+//
+// Such casting results in type punning: holding an object in memory of one 
type
+// and reading its bits back using a different type. A `bit_cast()` avoids this
+// issue by implementing its casts using `memcpy()`, which avoids introducing
+// this undefined behavior.
+template <typename Dest, typename Source>
+inline Dest bit_cast(const Source& source) {
+  static_assert(sizeof(Dest) == sizeof(Source),
+                "Source and destination types should have equal sizes.");
+
+  Dest dest;
+  memcpy(&dest, &source, sizeof(dest));
+  return dest;
+}
+
+}  // namespace absl
+
+#endif  // ABSL_BASE_CASTS_H_

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/config.h
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diff --git a/libraries/ostrich/backend/3rdparty/abseil/absl/base/config.h 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/config.h
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+//
+// 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
+//
+//      http://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.
+//
+// 
-----------------------------------------------------------------------------
+// File: config.h
+// 
-----------------------------------------------------------------------------
+//
+// This header file defines a set of macros for checking the presence of
+// important compiler and platform features. Such macros can be used to
+// produce portable code by parameterizing compilation based on the presence or
+// lack of a given feature.
+//
+// We define a "feature" as some interface we wish to program to: for example,
+// a library function or system call. A value of `1` indicates support for
+// that feature; any other value indicates the feature support is undefined.
+//
+// Example:
+//
+// Suppose a programmer wants to write a program that uses the 'mmap()' system
+// call. The Abseil macro for that feature (`ABSL_HAVE_MMAP`) allows you to
+// selectively include the `mmap.h` header and bracket code using that feature
+// in the macro:
+//
+//   #include "absl/base/config.h"
+//
+//   #ifdef ABSL_HAVE_MMAP
+//   #include "sys/mman.h"
+//   #endif  //ABSL_HAVE_MMAP
+//
+//   ...
+//   #ifdef ABSL_HAVE_MMAP
+//   void *ptr = mmap(...);
+//   ...
+//   #endif  // ABSL_HAVE_MMAP
+
+#ifndef ABSL_BASE_CONFIG_H_
+#define ABSL_BASE_CONFIG_H_
+
+// Included for the __GLIBC__ macro (or similar macros on other systems).
+#include <limits.h>
+
+#ifdef __cplusplus
+// Included for __GLIBCXX__, _LIBCPP_VERSION
+#include <cstddef>
+#endif  // __cplusplus
+
+#if defined(__APPLE__)
+// Included for TARGET_OS_IPHONE, __IPHONE_OS_VERSION_MIN_REQUIRED,
+// __IPHONE_8_0.
+#include <Availability.h>
+#include <TargetConditionals.h>
+#endif
+
+#include "absl/base/policy_checks.h"
+
+// 
-----------------------------------------------------------------------------
+// Compiler Feature Checks
+// 
-----------------------------------------------------------------------------
+
+// ABSL_HAVE_BUILTIN()
+//
+// Checks whether the compiler supports a Clang Feature Checking Macro, and if
+// so, checks whether it supports the provided builtin function "x" where x
+// is one of the functions noted in
+// https://clang.llvm.org/docs/LanguageExtensions.html
+//
+// Note: Use this macro to avoid an extra level of #ifdef __has_builtin check.
+// http://releases.llvm.org/3.3/tools/clang/docs/LanguageExtensions.html
+#ifdef __has_builtin
+#define ABSL_HAVE_BUILTIN(x) __has_builtin(x)
+#else
+#define ABSL_HAVE_BUILTIN(x) 0
+#endif
+
+// ABSL_HAVE_TLS is defined to 1 when __thread should be supported.
+// We assume __thread is supported on Linux when compiled with Clang or 
compiled
+// against libstdc++ with _GLIBCXX_HAVE_TLS defined.
+#ifdef ABSL_HAVE_TLS
+#error ABSL_HAVE_TLS cannot be directly set
+#elif defined(__linux__) && (defined(__clang__) || defined(_GLIBCXX_HAVE_TLS))
+#define ABSL_HAVE_TLS 1
+#endif
+
+// ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
+//
+// Checks whether `std::is_trivially_destructible<T>` is supported.
+//
+// Notes: All supported compilers using libc++ support this feature, as does
+// gcc >= 4.8.1 using libstdc++, and Visual Studio.
+#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
+#error ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE cannot be directly set
+#elif defined(_LIBCPP_VERSION) ||                                        \
+    (!defined(__clang__) && defined(__GNUC__) && defined(__GLIBCXX__) && \
+     (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))) ||        \
+    defined(_MSC_VER)
+#define ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE 1
+#endif
+
+// ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE
+//
+// Checks whether `std::is_trivially_default_constructible<T>` and
+// `std::is_trivially_copy_constructible<T>` are supported.
+
+// ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
+//
+// Checks whether `std::is_trivially_copy_assignable<T>` is supported.
+
+// Notes: Clang with libc++ supports these features, as does gcc >= 5.1 with
+// either libc++ or libstdc++, and Visual Studio.
+#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE)
+#error ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE cannot be directly set
+#elif defined(ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE)
+#error ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE cannot directly set
+#elif (defined(__clang__) && defined(_LIBCPP_VERSION)) ||        \
+    (!defined(__clang__) && defined(__GNUC__) &&                 \
+     (__GNUC__ > 5 || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)) && \
+     (defined(_LIBCPP_VERSION) || defined(__GLIBCXX__))) ||      \
+    defined(_MSC_VER)
+#define ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE 1
+#define ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE 1
+#endif
+
+// ABSL_HAVE_THREAD_LOCAL
+//
+// Checks whether C++11's `thread_local` storage duration specifier is
+// supported.
+#ifdef ABSL_HAVE_THREAD_LOCAL
+#error ABSL_HAVE_THREAD_LOCAL cannot be directly set
+#elif defined(__APPLE__)
+// Notes: Xcode's clang did not support `thread_local` until version
+// 8, and even then not for all iOS < 9.0. Also, Xcode 9.3 started disallowing
+// `thread_local` for 32-bit iOS simulator targeting iOS 9.x.
+// `__has_feature` is only supported by Clang so it has be inside
+// `defined(__APPLE__)` check.
+#if __has_feature(cxx_thread_local)
+#define ABSL_HAVE_THREAD_LOCAL 1
+#endif
+#else  // !defined(__APPLE__)
+#define ABSL_HAVE_THREAD_LOCAL 1
+#endif
+
+// There are platforms for which TLS should not be used even though the 
compiler
+// makes it seem like it's supported (Android NDK < r12b for example).
+// This is primarily because of linker problems and toolchain misconfiguration:
+// Abseil does not intend to support this indefinitely. Currently, the newest
+// toolchain that we intend to support that requires this behavior is the
+// r11 NDK - allowing for a 5 year support window on that means this option
+// is likely to be removed around June of 2021.
+// TLS isn't supported until NDK r12b per
+// https://developer.android.com/ndk/downloads/revision_history.html
+// Since NDK r16, `__NDK_MAJOR__` and `__NDK_MINOR__` are defined in
+// <android/ndk-version.h>. For NDK < r16, users should define these macros,
+// e.g. `-D__NDK_MAJOR__=11 -D__NKD_MINOR__=0` for NDK r11.
+#if defined(__ANDROID__) && defined(__clang__)
+#if __has_include(<android/ndk-version.h>)
+#include <android/ndk-version.h>
+#endif  // __has_include(<android/ndk-version.h>)
+#if defined(__ANDROID__) && defined(__clang__) && defined(__NDK_MAJOR__) && \
+    defined(__NDK_MINOR__) &&                                               \
+    ((__NDK_MAJOR__ < 12) || ((__NDK_MAJOR__ == 12) && (__NDK_MINOR__ < 1)))
+#undef ABSL_HAVE_TLS
+#undef ABSL_HAVE_THREAD_LOCAL
+#endif
+#endif  // defined(__ANDROID__) && defined(__clang__)
+
+// ABSL_HAVE_INTRINSIC_INT128
+//
+// Checks whether the __int128 compiler extension for a 128-bit integral type 
is
+// supported.
+//
+// Note: __SIZEOF_INT128__ is defined by Clang and GCC when __int128 is
+// supported, but we avoid using it in certain cases:
+// * On Clang:
+//   * Building using Clang for Windows, where the Clang runtime library has
+//     128-bit support only on LP64 architectures, but Windows is LLP64.
+//   * Building for aarch64, where __int128 exists but has exhibits a sporadic
+//     compiler crashing bug.
+// * On Nvidia's nvcc:
+//   * nvcc also defines __GNUC__ and __SIZEOF_INT128__, but not all versions
+//     actually support __int128.
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+#error ABSL_HAVE_INTRINSIC_INT128 cannot be directly set
+#elif defined(__SIZEOF_INT128__)
+#if (defined(__clang__) && !defined(_WIN32) && !defined(__aarch64__)) || \
+    (defined(__CUDACC__) && __CUDACC_VER_MAJOR__ >= 9) ||                \
+    (defined(__GNUC__) && !defined(__clang__) && !defined(__CUDACC__))
+#define ABSL_HAVE_INTRINSIC_INT128 1
+#elif defined(__CUDACC__)
+// __CUDACC_VER__ is a full version number before CUDA 9, and is defined to a
+// std::string explaining that it has been removed starting with CUDA 9. We use
+// nested #ifs because there is no short-circuiting in the preprocessor.
+// NOTE: `__CUDACC__` could be undefined while `__CUDACC_VER__` is defined.
+#if __CUDACC_VER__ >= 70000
+#define ABSL_HAVE_INTRINSIC_INT128 1
+#endif  // __CUDACC_VER__ >= 70000
+#endif  // defined(__CUDACC__)
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+// ABSL_HAVE_EXCEPTIONS
+//
+// Checks whether the compiler both supports and enables exceptions. Many
+// compilers support a "no exceptions" mode that disables exceptions.
+//
+// Generally, when ABSL_HAVE_EXCEPTIONS is not defined:
+//
+// * Code using `throw` and `try` may not compile.
+// * The `noexcept` specifier will still compile and behave as normal.
+// * The `noexcept` operator may still return `false`.
+//
+// For further details, consult the compiler's documentation.
+#ifdef ABSL_HAVE_EXCEPTIONS
+#error ABSL_HAVE_EXCEPTIONS cannot be directly set.
+
+#elif defined(__clang__)
+// TODO(calabrese)
+// Switch to using __cpp_exceptions when we no longer support versions < 3.6.
+// For details on this check, see:
+//   
http://releases.llvm.org/3.6.0/tools/clang/docs/ReleaseNotes.html#the-exceptions-macro
+#if defined(__EXCEPTIONS) && __has_feature(cxx_exceptions)
+#define ABSL_HAVE_EXCEPTIONS 1
+#endif  // defined(__EXCEPTIONS) && __has_feature(cxx_exceptions)
+
+// Handle remaining special cases and default to exceptions being supported.
+#elif !(defined(__GNUC__) && (__GNUC__ < 5) && !defined(__EXCEPTIONS)) &&    \
+    !(defined(__GNUC__) && (__GNUC__ >= 5) && !defined(__cpp_exceptions)) && \
+    !(defined(_MSC_VER) && !defined(_CPPUNWIND))
+#define ABSL_HAVE_EXCEPTIONS 1
+#endif
+
+// 
-----------------------------------------------------------------------------
+// Platform Feature Checks
+// 
-----------------------------------------------------------------------------
+
+// Currently supported operating systems and associated preprocessor
+// symbols:
+//
+//   Linux and Linux-derived           __linux__
+//   Android                           __ANDROID__ (implies __linux__)
+//   Linux (non-Android)               __linux__ && !__ANDROID__
+//   Darwin (Mac OS X and iOS)         __APPLE__
+//   Akaros (http://akaros.org)        __ros__
+//   Windows                           _WIN32
+//   NaCL                              __native_client__
+//   AsmJS                             __asmjs__
+//   WebAssembly                       __wasm__
+//   Fuchsia                           __Fuchsia__
+//
+// Note that since Android defines both __ANDROID__ and __linux__, one
+// may probe for either Linux or Android by simply testing for __linux__.
+
+// ABSL_HAVE_MMAP
+//
+// Checks whether the platform has an mmap(2) implementation as defined in
+// POSIX.1-2001.
+#ifdef ABSL_HAVE_MMAP
+#error ABSL_HAVE_MMAP cannot be directly set
+#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) ||   \
+    defined(__ros__) || defined(__native_client__) || defined(__asmjs__) || \
+    defined(__wasm__) || defined(__Fuchsia__)
+#define ABSL_HAVE_MMAP 1
+#endif
+
+// ABSL_HAVE_PTHREAD_GETSCHEDPARAM
+//
+// Checks whether the platform implements the pthread_(get|set)schedparam(3)
+// functions as defined in POSIX.1-2001.
+#ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
+#error ABSL_HAVE_PTHREAD_GETSCHEDPARAM cannot be directly set
+#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
+    defined(__ros__)
+#define ABSL_HAVE_PTHREAD_GETSCHEDPARAM 1
+#endif
+
+// ABSL_HAVE_SCHED_YIELD
+//
+// Checks whether the platform implements sched_yield(2) as defined in
+// POSIX.1-2001.
+#ifdef ABSL_HAVE_SCHED_YIELD
+#error ABSL_HAVE_SCHED_YIELD cannot be directly set
+#elif defined(__linux__) || defined(__ros__) || defined(__native_client__)
+#define ABSL_HAVE_SCHED_YIELD 1
+#endif
+
+// ABSL_HAVE_SEMAPHORE_H
+//
+// Checks whether the platform supports the <semaphore.h> header and 
sem_open(3)
+// family of functions as standardized in POSIX.1-2001.
+//
+// Note: While Apple provides <semaphore.h> for both iOS and macOS, it is
+// explicitly deprecated and will cause build failures if enabled for those
+// platforms.  We side-step the issue by not defining it here for Apple
+// platforms.
+#ifdef ABSL_HAVE_SEMAPHORE_H
+#error ABSL_HAVE_SEMAPHORE_H cannot be directly set
+#elif defined(__linux__) || defined(__ros__)
+#define ABSL_HAVE_SEMAPHORE_H 1
+#endif
+
+// ABSL_HAVE_ALARM
+//
+// Checks whether the platform supports the <signal.h> header and alarm(2)
+// function as standardized in POSIX.1-2001.
+#ifdef ABSL_HAVE_ALARM
+#error ABSL_HAVE_ALARM cannot be directly set
+#elif defined(__GOOGLE_GRTE_VERSION__)
+// feature tests for Google's GRTE
+#define ABSL_HAVE_ALARM 1
+#elif defined(__GLIBC__)
+// feature test for glibc
+#define ABSL_HAVE_ALARM 1
+#elif defined(_MSC_VER)
+// feature tests for Microsoft's library
+#elif defined(__native_client__)
+#else
+// other standard libraries
+#define ABSL_HAVE_ALARM 1
+#endif
+
+// ABSL_IS_LITTLE_ENDIAN
+// ABSL_IS_BIG_ENDIAN
+//
+// Checks the endianness of the platform.
+//
+// Notes: uses the built in endian macros provided by GCC (since 4.6) and
+// Clang (since 3.2); see
+// https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html.
+// Otherwise, if _WIN32, assume little endian. Otherwise, bail with an error.
+#if defined(ABSL_IS_BIG_ENDIAN)
+#error "ABSL_IS_BIG_ENDIAN cannot be directly set."
+#endif
+#if defined(ABSL_IS_LITTLE_ENDIAN)
+#error "ABSL_IS_LITTLE_ENDIAN cannot be directly set."
+#endif
+
+#if (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && \
+     __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+#define ABSL_IS_LITTLE_ENDIAN 1
+#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && \
+    __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define ABSL_IS_BIG_ENDIAN 1
+#elif defined(_WIN32)
+#define ABSL_IS_LITTLE_ENDIAN 1
+#else
+#error "absl endian detection needs to be set up for your compiler"
+#endif
+
+// ABSL_HAVE_STD_ANY
+//
+// Checks whether C++17 std::any is available by checking whether <any> exists.
+#ifdef ABSL_HAVE_STD_ANY
+#error "ABSL_HAVE_STD_ANY cannot be directly set."
+#endif
+
+#ifdef __has_include
+#if __has_include(<any>) && __cplusplus >= 201703L
+#define ABSL_HAVE_STD_ANY 1
+#endif
+#endif
+
+// ABSL_HAVE_STD_OPTIONAL
+//
+// Checks whether C++17 std::optional is available.
+#ifdef ABSL_HAVE_STD_OPTIONAL
+#error "ABSL_HAVE_STD_OPTIONAL cannot be directly set."
+#endif
+
+#ifdef __has_include
+#if __has_include(<optional>) && __cplusplus >= 201703L
+#define ABSL_HAVE_STD_OPTIONAL 1
+#endif
+#endif
+
+// ABSL_HAVE_STD_VARIANT
+//
+// Checks whether C++17 std::variant is available.
+#ifdef ABSL_HAVE_STD_VARIANT
+#error "ABSL_HAVE_STD_VARIANT cannot be directly set."
+#endif
+
+#ifdef __has_include
+#if __has_include(<variant>) && __cplusplus >= 201703L
+#define ABSL_HAVE_STD_VARIANT 1
+#endif
+#endif
+
+// ABSL_HAVE_STD_STRING_VIEW
+//
+// Checks whether C++17 std::string_view is available.
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#error "ABSL_HAVE_STD_STRING_VIEW cannot be directly set."
+#endif
+
+#ifdef __has_include
+#if __has_include(<string_view>) && __cplusplus >= 201703L
+#define ABSL_HAVE_STD_STRING_VIEW 1
+#endif
+#endif
+
+// For MSVC, `__has_include` is supported in VS 2017 15.3, which is later than
+// the support for <optional>, <any>, <string_view>, <variant>. So we use
+// _MSC_VER to check whether we have VS 2017 RTM (when <optional>, <any>,
+// <string_view>, <variant> is implemented) or higher. Also, `__cplusplus` is
+// not correctly set by MSVC, so we use `_MSVC_LANG` to check the language
+// version.
+// TODO(zhangxy): fix tests before enabling aliasing for `std::any`,
+// `std::string_view`.
+#if defined(_MSC_VER) && _MSC_VER >= 1910 && \
+    ((defined(_MSVC_LANG) && _MSVC_LANG > 201402) || __cplusplus > 201402)
+// #define ABSL_HAVE_STD_ANY 1
+#define ABSL_HAVE_STD_OPTIONAL 1
+#define ABSL_HAVE_STD_VARIANT 1
+// #define ABSL_HAVE_STD_STRING_VIEW 1
+#endif
+
+#endif  // ABSL_BASE_CONFIG_H_

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/config_test.cc
----------------------------------------------------------------------
diff --git a/libraries/ostrich/backend/3rdparty/abseil/absl/base/config_test.cc 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/config_test.cc
new file mode 100644
index 0000000..c839712
--- /dev/null
+++ b/libraries/ostrich/backend/3rdparty/abseil/absl/base/config_test.cc
@@ -0,0 +1,60 @@
+// 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
+//
+//      http://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/config.h"
+
+#include <cstdint>
+
+#include "gtest/gtest.h"
+#include "absl/synchronization/internal/thread_pool.h"
+
+namespace {
+
+TEST(ConfigTest, Endianness) {
+  union {
+    uint32_t value;
+    uint8_t data[sizeof(uint32_t)];
+  } number;
+  number.data[0] = 0x00;
+  number.data[1] = 0x01;
+  number.data[2] = 0x02;
+  number.data[3] = 0x03;
+#if defined(ABSL_IS_LITTLE_ENDIAN) && defined(ABSL_IS_BIG_ENDIAN)
+#error Both ABSL_IS_LITTLE_ENDIAN and ABSL_IS_BIG_ENDIAN are defined
+#elif defined(ABSL_IS_LITTLE_ENDIAN)
+  EXPECT_EQ(UINT32_C(0x03020100), number.value);
+#elif defined(ABSL_IS_BIG_ENDIAN)
+  EXPECT_EQ(UINT32_C(0x00010203), number.value);
+#else
+#error Unknown endianness
+#endif
+}
+
+#if defined(ABSL_HAVE_THREAD_LOCAL)
+TEST(ConfigTest, ThreadLocal) {
+  static thread_local int mine_mine_mine = 16;
+  EXPECT_EQ(16, mine_mine_mine);
+  {
+    absl::synchronization_internal::ThreadPool pool(1);
+    pool.Schedule([&] {
+      EXPECT_EQ(16, mine_mine_mine);
+      mine_mine_mine = 32;
+      EXPECT_EQ(32, mine_mine_mine);
+    });
+  }
+  EXPECT_EQ(16, mine_mine_mine);
+}
+#endif
+
+}  // namespace

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.cc
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.cc 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.cc
new file mode 100644
index 0000000..08c27e5
--- /dev/null
+++ b/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.cc
@@ -0,0 +1,129 @@
+// 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
+//
+//      http://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 <stdlib.h>
+#include <string.h>
+
+#include "absl/base/dynamic_annotations.h"
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
+/* Compiler-based ThreadSanitizer defines
+   DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL = 1
+   and provides its own definitions of the functions. */
+
+#ifndef DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL
+# define DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL 0
+#endif
+
+/* Each function is empty and called (via a macro) only in debug mode.
+   The arguments are captured by dynamic tools at runtime. */
+
+#if DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL == 0 && !defined(__native_client__)
+
+#if __has_feature(memory_sanitizer)
+#include <sanitizer/msan_interface.h>
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void AnnotateRWLockCreate(const char *, int,
+                          const volatile void *){}
+void AnnotateRWLockDestroy(const char *, int,
+                           const volatile void *){}
+void AnnotateRWLockAcquired(const char *, int,
+                            const volatile void *, long){}
+void AnnotateRWLockReleased(const char *, int,
+                            const volatile void *, long){}
+void AnnotateBenignRace(const char *, int,
+                        const volatile void *,
+                        const char *){}
+void AnnotateBenignRaceSized(const char *, int,
+                             const volatile void *,
+                             size_t,
+                             const char *) {}
+void AnnotateThreadName(const char *, int,
+                        const char *){}
+void AnnotateIgnoreReadsBegin(const char *, int){}
+void AnnotateIgnoreReadsEnd(const char *, int){}
+void AnnotateIgnoreWritesBegin(const char *, int){}
+void AnnotateIgnoreWritesEnd(const char *, int){}
+void AnnotateEnableRaceDetection(const char *, int, int){}
+void AnnotateMemoryIsInitialized(const char *, int,
+                                 const volatile void *mem, size_t size) {
+#if __has_feature(memory_sanitizer)
+  __msan_unpoison(mem, size);
+#else
+  (void)mem;
+  (void)size;
+#endif
+}
+
+void AnnotateMemoryIsUninitialized(const char *, int,
+                                   const volatile void *mem, size_t size) {
+#if __has_feature(memory_sanitizer)
+  __msan_allocated_memory(mem, size);
+#else
+  (void)mem;
+  (void)size;
+#endif
+}
+
+static int GetRunningOnValgrind(void) {
+#ifdef RUNNING_ON_VALGRIND
+  if (RUNNING_ON_VALGRIND) return 1;
+#endif
+  char *running_on_valgrind_str = getenv("RUNNING_ON_VALGRIND");
+  if (running_on_valgrind_str) {
+    return strcmp(running_on_valgrind_str, "0") != 0;
+  }
+  return 0;
+}
+
+/* See the comments in dynamic_annotations.h */
+int RunningOnValgrind(void) {
+  static volatile int running_on_valgrind = -1;
+  int local_running_on_valgrind = running_on_valgrind;
+  /* C doesn't have thread-safe initialization of statics, and we
+     don't want to depend on pthread_once here, so hack it. */
+  ANNOTATE_BENIGN_RACE(&running_on_valgrind, "safe hack");
+  if (local_running_on_valgrind == -1)
+    running_on_valgrind = local_running_on_valgrind = GetRunningOnValgrind();
+  return local_running_on_valgrind;
+}
+
+/* See the comments in dynamic_annotations.h */
+double ValgrindSlowdown(void) {
+  /* Same initialization hack as in RunningOnValgrind(). */
+  static volatile double slowdown = 0.0;
+  double local_slowdown = slowdown;
+  ANNOTATE_BENIGN_RACE(&slowdown, "safe hack");
+  if (RunningOnValgrind() == 0) {
+    return 1.0;
+  }
+  if (local_slowdown == 0.0) {
+    char *env = getenv("VALGRIND_SLOWDOWN");
+    slowdown = local_slowdown = env ? atof(env) : 50.0;
+  }
+  return local_slowdown;
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+#endif  /* DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL == 0 */

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.h
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.h 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.h
new file mode 100644
index 0000000..3b6d6ef
--- /dev/null
+++ b/libraries/ostrich/backend/3rdparty/abseil/absl/base/dynamic_annotations.h
@@ -0,0 +1,409 @@
+/*
+ *  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
+ *
+ *      http://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.
+ */
+/* This file defines dynamic annotations for use with dynamic analysis
+   tool such as valgrind, PIN, etc.
+
+   Dynamic annotation is a source code annotation that affects
+   the generated code (that is, the annotation is not a comment).
+   Each such annotation is attached to a particular
+   instruction and/or to a particular object (address) in the program.
+
+   The annotations that should be used by users are macros in all upper-case
+   (e.g., ANNOTATE_THREAD_NAME).
+
+   Actual implementation of these macros may differ depending on the
+   dynamic analysis tool being used.
+
+   This file supports the following configurations:
+   - Dynamic Annotations enabled (with static thread-safety warnings disabled).
+     In this case, macros expand to functions implemented by Thread Sanitizer,
+     when building with TSan. When not provided an external implementation,
+     dynamic_annotations.cc provides no-op implementations.
+
+   - Static Clang thread-safety warnings enabled.
+     When building with a Clang compiler that supports thread-safety warnings,
+     a subset of annotations can be statically-checked at compile-time. We
+     expand these macros to static-inline functions that can be analyzed for
+     thread-safety, but afterwards elided when building the final binary.
+
+   - All annotations are disabled.
+     If neither Dynamic Annotations nor Clang thread-safety warnings are
+     enabled, then all annotation-macros expand to empty. */
+
+#ifndef ABSL_BASE_DYNAMIC_ANNOTATIONS_H_
+#define ABSL_BASE_DYNAMIC_ANNOTATIONS_H_
+
+#ifndef DYNAMIC_ANNOTATIONS_ENABLED
+# define DYNAMIC_ANNOTATIONS_ENABLED 0
+#endif
+
+#if defined(__native_client__)
+  #include "nacl/dynamic_annotations.h"
+
+  // Stub out the macros missing from the NaCl version.
+  #ifndef ANNOTATE_CONTIGUOUS_CONTAINER
+    #define ANNOTATE_CONTIGUOUS_CONTAINER(beg, end, old_mid, new_mid)
+  #endif
+  #ifndef ANNOTATE_RWLOCK_CREATE_STATIC
+    #define ANNOTATE_RWLOCK_CREATE_STATIC(lock)
+  #endif
+  #ifndef ADDRESS_SANITIZER_REDZONE
+    #define ADDRESS_SANITIZER_REDZONE(name)
+  #endif
+  #ifndef ANNOTATE_MEMORY_IS_UNINITIALIZED
+    #define ANNOTATE_MEMORY_IS_UNINITIALIZED(address, size)
+  #endif
+
+#else /* !__native_client__ */
+
+#if DYNAMIC_ANNOTATIONS_ENABLED != 0
+
+  /* -------------------------------------------------------------
+     Annotations that suppress errors.  It is usually better to express the
+     program's synchronization using the other annotations, but these can
+     be used when all else fails. */
+
+  /* Report that we may have a benign race at "pointer", with size
+     "sizeof(*(pointer))". "pointer" must be a non-void* pointer.  Insert at 
the
+     point where "pointer" has been allocated, preferably close to the point
+     where the race happens.  See also ANNOTATE_BENIGN_RACE_STATIC. */
+  #define ANNOTATE_BENIGN_RACE(pointer, description) \
+    AnnotateBenignRaceSized(__FILE__, __LINE__, pointer, \
+                            sizeof(*(pointer)), description)
+
+  /* Same as ANNOTATE_BENIGN_RACE(address, description), but applies to
+     the memory range [address, address+size). */
+  #define ANNOTATE_BENIGN_RACE_SIZED(address, size, description) \
+    AnnotateBenignRaceSized(__FILE__, __LINE__, address, size, description)
+
+  /* Enable (enable!=0) or disable (enable==0) race detection for all threads.
+     This annotation could be useful if you want to skip expensive race 
analysis
+     during some period of program execution, e.g. during initialization. */
+  #define ANNOTATE_ENABLE_RACE_DETECTION(enable) \
+    AnnotateEnableRaceDetection(__FILE__, __LINE__, enable)
+
+  /* -------------------------------------------------------------
+     Annotations useful for debugging. */
+
+  /* Report the current thread name to a race detector. */
+  #define ANNOTATE_THREAD_NAME(name) \
+    AnnotateThreadName(__FILE__, __LINE__, name)
+
+  /* -------------------------------------------------------------
+     Annotations useful when implementing locks.  They are not
+     normally needed by modules that merely use locks.
+     The "lock" argument is a pointer to the lock object. */
+
+  /* Report that a lock has been created at address "lock". */
+  #define ANNOTATE_RWLOCK_CREATE(lock) \
+    AnnotateRWLockCreate(__FILE__, __LINE__, lock)
+
+  /* Report that a linker initialized lock has been created at address "lock".
+   */
+#ifdef THREAD_SANITIZER
+  #define ANNOTATE_RWLOCK_CREATE_STATIC(lock) \
+    AnnotateRWLockCreateStatic(__FILE__, __LINE__, lock)
+#else
+  #define ANNOTATE_RWLOCK_CREATE_STATIC(lock) ANNOTATE_RWLOCK_CREATE(lock)
+#endif
+
+  /* Report that the lock at address "lock" is about to be destroyed. */
+  #define ANNOTATE_RWLOCK_DESTROY(lock) \
+    AnnotateRWLockDestroy(__FILE__, __LINE__, lock)
+
+  /* Report that the lock at address "lock" has been acquired.
+     is_w=1 for writer lock, is_w=0 for reader lock. */
+  #define ANNOTATE_RWLOCK_ACQUIRED(lock, is_w) \
+    AnnotateRWLockAcquired(__FILE__, __LINE__, lock, is_w)
+
+  /* Report that the lock at address "lock" is about to be released. */
+  #define ANNOTATE_RWLOCK_RELEASED(lock, is_w) \
+    AnnotateRWLockReleased(__FILE__, __LINE__, lock, is_w)
+
+#else  /* DYNAMIC_ANNOTATIONS_ENABLED == 0 */
+
+  #define ANNOTATE_RWLOCK_CREATE(lock) /* empty */
+  #define ANNOTATE_RWLOCK_CREATE_STATIC(lock) /* empty */
+  #define ANNOTATE_RWLOCK_DESTROY(lock) /* empty */
+  #define ANNOTATE_RWLOCK_ACQUIRED(lock, is_w) /* empty */
+  #define ANNOTATE_RWLOCK_RELEASED(lock, is_w) /* empty */
+  #define ANNOTATE_BENIGN_RACE(address, description) /* empty */
+  #define ANNOTATE_BENIGN_RACE_SIZED(address, size, description) /* empty */
+  #define ANNOTATE_THREAD_NAME(name) /* empty */
+  #define ANNOTATE_ENABLE_RACE_DETECTION(enable) /* empty */
+
+#endif  /* DYNAMIC_ANNOTATIONS_ENABLED */
+
+/* These annotations are also made available to LLVM's Memory Sanitizer */
+#if DYNAMIC_ANNOTATIONS_ENABLED == 1 || defined(MEMORY_SANITIZER)
+  #define ANNOTATE_MEMORY_IS_INITIALIZED(address, size) \
+    AnnotateMemoryIsInitialized(__FILE__, __LINE__, address, size)
+
+  #define ANNOTATE_MEMORY_IS_UNINITIALIZED(address, size) \
+    AnnotateMemoryIsUninitialized(__FILE__, __LINE__, address, size)
+#else
+  #define ANNOTATE_MEMORY_IS_INITIALIZED(address, size) /* empty */
+  #define ANNOTATE_MEMORY_IS_UNINITIALIZED(address, size) /* empty */
+#endif  /* DYNAMIC_ANNOTATIONS_ENABLED || MEMORY_SANITIZER */
+/* TODO(delesley) -- Replace __CLANG_SUPPORT_DYN_ANNOTATION__ with the
+   appropriate feature ID. */
+#if defined(__clang__) && (!defined(SWIG)) \
+    && defined(__CLANG_SUPPORT_DYN_ANNOTATION__)
+
+  #if DYNAMIC_ANNOTATIONS_ENABLED == 0
+    #define ANNOTALYSIS_ENABLED
+  #endif
+
+  /* When running in opt-mode, GCC will issue a warning, if these attributes 
are
+     compiled. Only include them when compiling using Clang. */
+  #define ATTRIBUTE_IGNORE_READS_BEGIN \
+      __attribute((exclusive_lock_function("*")))
+  #define ATTRIBUTE_IGNORE_READS_END \
+      __attribute((unlock_function("*")))
+#else
+  #define ATTRIBUTE_IGNORE_READS_BEGIN  /* empty */
+  #define ATTRIBUTE_IGNORE_READS_END  /* empty */
+#endif  /* defined(__clang__) && ... */
+
+#if (DYNAMIC_ANNOTATIONS_ENABLED != 0) || defined(ANNOTALYSIS_ENABLED)
+  #define ANNOTATIONS_ENABLED
+#endif
+
+#if (DYNAMIC_ANNOTATIONS_ENABLED != 0)
+
+  /* Request the analysis tool to ignore all reads in the current thread
+     until ANNOTATE_IGNORE_READS_END is called.
+     Useful to ignore intentional racey reads, while still checking
+     other reads and all writes.
+     See also ANNOTATE_UNPROTECTED_READ. */
+  #define ANNOTATE_IGNORE_READS_BEGIN() \
+    AnnotateIgnoreReadsBegin(__FILE__, __LINE__)
+
+  /* Stop ignoring reads. */
+  #define ANNOTATE_IGNORE_READS_END() \
+    AnnotateIgnoreReadsEnd(__FILE__, __LINE__)
+
+  /* Similar to ANNOTATE_IGNORE_READS_BEGIN, but ignore writes instead. */
+  #define ANNOTATE_IGNORE_WRITES_BEGIN() \
+    AnnotateIgnoreWritesBegin(__FILE__, __LINE__)
+
+  /* Stop ignoring writes. */
+  #define ANNOTATE_IGNORE_WRITES_END() \
+    AnnotateIgnoreWritesEnd(__FILE__, __LINE__)
+
+/* Clang provides limited support for static thread-safety analysis
+   through a feature called Annotalysis. We configure macro-definitions
+   according to whether Annotalysis support is available. */
+#elif defined(ANNOTALYSIS_ENABLED)
+
+  #define ANNOTATE_IGNORE_READS_BEGIN() \
+    StaticAnnotateIgnoreReadsBegin(__FILE__, __LINE__)
+
+  #define ANNOTATE_IGNORE_READS_END() \
+    StaticAnnotateIgnoreReadsEnd(__FILE__, __LINE__)
+
+  #define ANNOTATE_IGNORE_WRITES_BEGIN() \
+    StaticAnnotateIgnoreWritesBegin(__FILE__, __LINE__)
+
+  #define ANNOTATE_IGNORE_WRITES_END() \
+    StaticAnnotateIgnoreWritesEnd(__FILE__, __LINE__)
+
+#else
+  #define ANNOTATE_IGNORE_READS_BEGIN()  /* empty */
+  #define ANNOTATE_IGNORE_READS_END()  /* empty */
+  #define ANNOTATE_IGNORE_WRITES_BEGIN()  /* empty */
+  #define ANNOTATE_IGNORE_WRITES_END()  /* empty */
+#endif
+
+/* Implement the ANNOTATE_IGNORE_READS_AND_WRITES_* annotations using the more
+   primitive annotations defined above. */
+#if defined(ANNOTATIONS_ENABLED)
+
+  /* Start ignoring all memory accesses (both reads and writes). */
+  #define ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN() \
+    do {                                           \
+      ANNOTATE_IGNORE_READS_BEGIN();               \
+      ANNOTATE_IGNORE_WRITES_BEGIN();              \
+    }while (0)
+
+  /* Stop ignoring both reads and writes. */
+  #define ANNOTATE_IGNORE_READS_AND_WRITES_END()   \
+    do {                                           \
+      ANNOTATE_IGNORE_WRITES_END();                \
+      ANNOTATE_IGNORE_READS_END();                 \
+    }while (0)
+
+#else
+  #define ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN()  /* empty */
+  #define ANNOTATE_IGNORE_READS_AND_WRITES_END()  /* empty */
+#endif
+
+/* Use the macros above rather than using these functions directly. */
+#include <stddef.h>
+#ifdef __cplusplus
+extern "C" {
+#endif
+void AnnotateRWLockCreate(const char *file, int line,
+                          const volatile void *lock);
+void AnnotateRWLockCreateStatic(const char *file, int line,
+                          const volatile void *lock);
+void AnnotateRWLockDestroy(const char *file, int line,
+                           const volatile void *lock);
+void AnnotateRWLockAcquired(const char *file, int line,
+                            const volatile void *lock, long is_w);  /* NOLINT 
*/
+void AnnotateRWLockReleased(const char *file, int line,
+                            const volatile void *lock, long is_w);  /* NOLINT 
*/
+void AnnotateBenignRace(const char *file, int line,
+                        const volatile void *address,
+                        const char *description);
+void AnnotateBenignRaceSized(const char *file, int line,
+                        const volatile void *address,
+                        size_t size,
+                        const char *description);
+void AnnotateThreadName(const char *file, int line,
+                        const char *name);
+void AnnotateEnableRaceDetection(const char *file, int line, int enable);
+void AnnotateMemoryIsInitialized(const char *file, int line,
+                                 const volatile void *mem, size_t size);
+void AnnotateMemoryIsUninitialized(const char *file, int line,
+                                   const volatile void *mem, size_t size);
+
+/* Annotations expand to these functions, when Dynamic Annotations are enabled.
+   These functions are either implemented as no-op calls, if no Sanitizer is
+   attached, or provided with externally-linked implementations by a library
+   like ThreadSanitizer. */
+void AnnotateIgnoreReadsBegin(const char *file, int line)
+    ATTRIBUTE_IGNORE_READS_BEGIN;
+void AnnotateIgnoreReadsEnd(const char *file, int line)
+    ATTRIBUTE_IGNORE_READS_END;
+void AnnotateIgnoreWritesBegin(const char *file, int line);
+void AnnotateIgnoreWritesEnd(const char *file, int line);
+
+#if defined(ANNOTALYSIS_ENABLED)
+/* When Annotalysis is enabled without Dynamic Annotations, the use of
+   static-inline functions allows the annotations to be read at compile-time,
+   while still letting the compiler elide the functions from the final build.
+
+   TODO(delesley) -- The exclusive lock here ignores writes as well, but
+   allows IGNORE_READS_AND_WRITES to work properly. */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
+static inline void StaticAnnotateIgnoreReadsBegin(const char *file, int line)
+    ATTRIBUTE_IGNORE_READS_BEGIN { (void)file; (void)line; }
+static inline void StaticAnnotateIgnoreReadsEnd(const char *file, int line)
+    ATTRIBUTE_IGNORE_READS_END { (void)file; (void)line; }
+static inline void StaticAnnotateIgnoreWritesBegin(
+    const char *file, int line) { (void)file; (void)line; }
+static inline void StaticAnnotateIgnoreWritesEnd(
+    const char *file, int line) { (void)file; (void)line; }
+#pragma GCC diagnostic pop
+#endif
+
+/* Return non-zero value if running under valgrind.
+
+  If "valgrind.h" is included into dynamic_annotations.cc,
+  the regular valgrind mechanism will be used.
+  See http://valgrind.org/docs/manual/manual-core-adv.html about
+  RUNNING_ON_VALGRIND and other valgrind "client requests".
+  The file "valgrind.h" may be obtained by doing
+     svn co svn://svn.valgrind.org/valgrind/trunk/include
+
+  If for some reason you can't use "valgrind.h" or want to fake valgrind,
+  there are two ways to make this function return non-zero:
+    - Use environment variable: export RUNNING_ON_VALGRIND=1
+    - Make your tool intercept the function RunningOnValgrind() and
+      change its return value.
+ */
+int RunningOnValgrind(void);
+
+/* ValgrindSlowdown returns:
+    * 1.0, if (RunningOnValgrind() == 0)
+    * 50.0, if (RunningOnValgrind() != 0 && getenv("VALGRIND_SLOWDOWN") == 
NULL)
+    * atof(getenv("VALGRIND_SLOWDOWN")) otherwise
+   This function can be used to scale timeout values:
+   EXAMPLE:
+   for (;;) {
+     DoExpensiveBackgroundTask();
+     SleepForSeconds(5 * ValgrindSlowdown());
+   }
+ */
+double ValgrindSlowdown(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+/* ANNOTATE_UNPROTECTED_READ is the preferred way to annotate racey reads.
+
+     Instead of doing
+        ANNOTATE_IGNORE_READS_BEGIN();
+        ... = x;
+        ANNOTATE_IGNORE_READS_END();
+     one can use
+        ... = ANNOTATE_UNPROTECTED_READ(x); */
+#if defined(__cplusplus) && defined(ANNOTATIONS_ENABLED)
+template <typename T>
+inline T ANNOTATE_UNPROTECTED_READ(const volatile T &x) { /* NOLINT */
+  ANNOTATE_IGNORE_READS_BEGIN();
+  T res = x;
+  ANNOTATE_IGNORE_READS_END();
+  return res;
+  }
+#else
+  #define ANNOTATE_UNPROTECTED_READ(x) (x)
+#endif
+
+#if DYNAMIC_ANNOTATIONS_ENABLED != 0 && defined(__cplusplus)
+  /* Apply ANNOTATE_BENIGN_RACE_SIZED to a static variable. */
+  #define ANNOTATE_BENIGN_RACE_STATIC(static_var, description)        \
+    namespace {                                                       \
+      class static_var ## _annotator {                                \
+       public:                                                        \
+        static_var ## _annotator() {                                  \
+          ANNOTATE_BENIGN_RACE_SIZED(&static_var,                     \
+                                      sizeof(static_var),             \
+            # static_var ": " description);                           \
+        }                                                             \
+      };                                                              \
+      static static_var ## _annotator the ## static_var ## _annotator;\
+    }  // namespace
+#else /* DYNAMIC_ANNOTATIONS_ENABLED == 0 */
+  #define ANNOTATE_BENIGN_RACE_STATIC(static_var, description)  /* empty */
+#endif /* DYNAMIC_ANNOTATIONS_ENABLED */
+
+#ifdef ADDRESS_SANITIZER
+/* Describe the current state of a contiguous container such as e.g.
+ * std::vector or std::string. For more details see
+ * sanitizer/common_interface_defs.h, which is provided by the compiler. */
+#include <sanitizer/common_interface_defs.h>
+#define ANNOTATE_CONTIGUOUS_CONTAINER(beg, end, old_mid, new_mid) \
+  __sanitizer_annotate_contiguous_container(beg, end, old_mid, new_mid)
+#define ADDRESS_SANITIZER_REDZONE(name)         \
+  struct { char x[8] __attribute__ ((aligned (8))); } name
+#else
+#define ANNOTATE_CONTIGUOUS_CONTAINER(beg, end, old_mid, new_mid)
+#define ADDRESS_SANITIZER_REDZONE(name)
+#endif  // ADDRESS_SANITIZER
+
+/* Undefine the macros intended only in this file. */
+#undef ANNOTALYSIS_ENABLED
+#undef ANNOTATIONS_ENABLED
+#undef ATTRIBUTE_IGNORE_READS_BEGIN
+#undef ATTRIBUTE_IGNORE_READS_END
+
+#endif /* !__native_client__ */
+
+#endif  /* ABSL_BASE_DYNAMIC_ANNOTATIONS_H_ */

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/exception_safety_testing_test.cc
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/exception_safety_testing_test.cc
 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/exception_safety_testing_test.cc
new file mode 100644
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+++ 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/exception_safety_testing_test.cc
@@ -0,0 +1,842 @@
+// 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
+//
+//      http://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/exception_safety_testing.h"
+
+#include <cstddef>
+#include <exception>
+#include <iostream>
+#include <list>
+#include <type_traits>
+#include <vector>
+
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+#include "absl/memory/memory.h"
+
+namespace absl {
+namespace {
+using ::absl::exceptions_internal::SetCountdown;
+using ::absl::exceptions_internal::TestException;
+using ::absl::exceptions_internal::UnsetCountdown;
+
+// EXPECT_NO_THROW can't inspect the thrown inspection in general.
+template <typename F>
+void ExpectNoThrow(const F& f) {
+  try {
+    f();
+  } catch (TestException e) {
+    ADD_FAILURE() << "Unexpected exception thrown from " << e.what();
+  }
+}
+
+TEST(ThrowingValueTest, Throws) {
+  SetCountdown();
+  EXPECT_THROW(ThrowingValue<> bomb, TestException);
+
+  // It's not guaranteed that every operator only throws *once*.  The default
+  // ctor only throws once, though, so use it to make sure we only throw when
+  // the countdown hits 0
+  SetCountdown(2);
+  ExpectNoThrow([]() { ThrowingValue<> bomb; });
+  ExpectNoThrow([]() { ThrowingValue<> bomb; });
+  EXPECT_THROW(ThrowingValue<> bomb, TestException);
+
+  UnsetCountdown();
+}
+
+// Tests that an operation throws when the countdown is at 0, doesn't throw 
when
+// the countdown doesn't hit 0, and doesn't modify the state of the
+// ThrowingValue if it throws
+template <typename F>
+void TestOp(const F& f) {
+  ExpectNoThrow(f);
+
+  SetCountdown();
+  EXPECT_THROW(f(), TestException);
+  UnsetCountdown();
+}
+
+TEST(ThrowingValueTest, ThrowingCtors) {
+  ThrowingValue<> bomb;
+
+  TestOp([]() { ThrowingValue<> bomb(1); });
+  TestOp([&]() { ThrowingValue<> bomb1 = bomb; });
+  TestOp([&]() { ThrowingValue<> bomb1 = std::move(bomb); });
+}
+
+TEST(ThrowingValueTest, ThrowingAssignment) {
+  ThrowingValue<> bomb, bomb1;
+
+  TestOp([&]() { bomb = bomb1; });
+  TestOp([&]() { bomb = std::move(bomb1); });
+}
+
+TEST(ThrowingValueTest, ThrowingComparisons) {
+  ThrowingValue<> bomb1, bomb2;
+  TestOp([&]() { return bomb1 == bomb2; });
+  TestOp([&]() { return bomb1 != bomb2; });
+  TestOp([&]() { return bomb1 < bomb2; });
+  TestOp([&]() { return bomb1 <= bomb2; });
+  TestOp([&]() { return bomb1 > bomb2; });
+  TestOp([&]() { return bomb1 >= bomb2; });
+}
+
+TEST(ThrowingValueTest, ThrowingArithmeticOps) {
+  ThrowingValue<> bomb1(1), bomb2(2);
+
+  TestOp([&bomb1]() { +bomb1; });
+  TestOp([&bomb1]() { -bomb1; });
+  TestOp([&bomb1]() { ++bomb1; });
+  TestOp([&bomb1]() { bomb1++; });
+  TestOp([&bomb1]() { --bomb1; });
+  TestOp([&bomb1]() { bomb1--; });
+
+  TestOp([&]() { bomb1 + bomb2; });
+  TestOp([&]() { bomb1 - bomb2; });
+  TestOp([&]() { bomb1* bomb2; });
+  TestOp([&]() { bomb1 / bomb2; });
+  TestOp([&]() { bomb1 << 1; });
+  TestOp([&]() { bomb1 >> 1; });
+}
+
+TEST(ThrowingValueTest, ThrowingLogicalOps) {
+  ThrowingValue<> bomb1, bomb2;
+
+  TestOp([&bomb1]() { !bomb1; });
+  TestOp([&]() { bomb1&& bomb2; });
+  TestOp([&]() { bomb1 || bomb2; });
+}
+
+TEST(ThrowingValueTest, ThrowingBitwiseOps) {
+  ThrowingValue<> bomb1, bomb2;
+
+  TestOp([&bomb1]() { ~bomb1; });
+  TestOp([&]() { bomb1& bomb2; });
+  TestOp([&]() { bomb1 | bomb2; });
+  TestOp([&]() { bomb1 ^ bomb2; });
+}
+
+TEST(ThrowingValueTest, ThrowingCompoundAssignmentOps) {
+  ThrowingValue<> bomb1(1), bomb2(2);
+
+  TestOp([&]() { bomb1 += bomb2; });
+  TestOp([&]() { bomb1 -= bomb2; });
+  TestOp([&]() { bomb1 *= bomb2; });
+  TestOp([&]() { bomb1 /= bomb2; });
+  TestOp([&]() { bomb1 %= bomb2; });
+  TestOp([&]() { bomb1 &= bomb2; });
+  TestOp([&]() { bomb1 |= bomb2; });
+  TestOp([&]() { bomb1 ^= bomb2; });
+  TestOp([&]() { bomb1 *= bomb2; });
+}
+
+TEST(ThrowingValueTest, ThrowingStreamOps) {
+  ThrowingValue<> bomb;
+
+  TestOp([&]() { std::cin >> bomb; });
+  TestOp([&]() { std::cout << bomb; });
+}
+
+template <typename F>
+void TestAllocatingOp(const F& f) {
+  ExpectNoThrow(f);
+
+  SetCountdown();
+  EXPECT_THROW(f(), exceptions_internal::TestBadAllocException);
+  UnsetCountdown();
+}
+
+TEST(ThrowingValueTest, ThrowingAllocatingOps) {
+  // make_unique calls unqualified operator new, so these exercise the
+  // ThrowingValue overloads.
+  TestAllocatingOp([]() { return absl::make_unique<ThrowingValue<>>(1); });
+  TestAllocatingOp([]() { return absl::make_unique<ThrowingValue<>[]>(2); });
+}
+
+TEST(ThrowingValueTest, NonThrowingMoveCtor) {
+  ThrowingValue<NoThrow::kMoveCtor> nothrow_ctor;
+
+  SetCountdown();
+  ExpectNoThrow([&nothrow_ctor]() {
+    ThrowingValue<NoThrow::kMoveCtor> nothrow1 = std::move(nothrow_ctor);
+  });
+  UnsetCountdown();
+}
+
+TEST(ThrowingValueTest, NonThrowingMoveAssign) {
+  ThrowingValue<NoThrow::kMoveAssign> nothrow_assign1, nothrow_assign2;
+
+  SetCountdown();
+  ExpectNoThrow([&nothrow_assign1, &nothrow_assign2]() {
+    nothrow_assign1 = std::move(nothrow_assign2);
+  });
+  UnsetCountdown();
+}
+
+TEST(ThrowingValueTest, ThrowingSwap) {
+  ThrowingValue<> bomb1, bomb2;
+  TestOp([&]() { std::swap(bomb1, bomb2); });
+
+  ThrowingValue<NoThrow::kMoveCtor> bomb3, bomb4;
+  TestOp([&]() { std::swap(bomb3, bomb4); });
+
+  ThrowingValue<NoThrow::kMoveAssign> bomb5, bomb6;
+  TestOp([&]() { std::swap(bomb5, bomb6); });
+}
+
+TEST(ThrowingValueTest, NonThrowingSwap) {
+  ThrowingValue<NoThrow::kMoveAssign | NoThrow::kMoveCtor> bomb1, bomb2;
+  ExpectNoThrow([&]() { std::swap(bomb1, bomb2); });
+}
+
+TEST(ThrowingValueTest, NonThrowingAllocation) {
+  ThrowingValue<NoThrow::kAllocation>* allocated;
+  ThrowingValue<NoThrow::kAllocation>* array;
+
+  ExpectNoThrow([&allocated]() {
+    allocated = new ThrowingValue<NoThrow::kAllocation>(1);
+    delete allocated;
+  });
+  ExpectNoThrow([&array]() {
+    array = new ThrowingValue<NoThrow::kAllocation>[2];
+    delete[] array;
+  });
+}
+
+TEST(ThrowingValueTest, NonThrowingDelete) {
+  auto* allocated = new ThrowingValue<>(1);
+  auto* array = new ThrowingValue<>[2];
+
+  SetCountdown();
+  ExpectNoThrow([allocated]() { delete allocated; });
+  SetCountdown();
+  ExpectNoThrow([array]() { delete[] array; });
+
+  UnsetCountdown();
+}
+
+using Storage =
+    absl::aligned_storage_t<sizeof(ThrowingValue<>), alignof(ThrowingValue<>)>;
+
+TEST(ThrowingValueTest, NonThrowingPlacementDelete) {
+  constexpr int kArrayLen = 2;
+  // We intentionally create extra space to store the tag allocated by 
placement
+  // new[].
+  constexpr int kStorageLen = 4;
+
+  Storage buf;
+  Storage array_buf[kStorageLen];
+  auto* placed = new (&buf) ThrowingValue<>(1);
+  auto placed_array = new (&array_buf) ThrowingValue<>[kArrayLen];
+
+  SetCountdown();
+  ExpectNoThrow([placed, &buf]() {
+    placed->~ThrowingValue<>();
+    ThrowingValue<>::operator delete(placed, &buf);
+  });
+
+  SetCountdown();
+  ExpectNoThrow([&, placed_array]() {
+    for (int i = 0; i < kArrayLen; ++i) placed_array[i].~ThrowingValue<>();
+    ThrowingValue<>::operator delete[](placed_array, &array_buf);
+  });
+
+  UnsetCountdown();
+}
+
+TEST(ThrowingValueTest, NonThrowingDestructor) {
+  auto* allocated = new ThrowingValue<>();
+
+  SetCountdown();
+  ExpectNoThrow([allocated]() { delete allocated; });
+  UnsetCountdown();
+}
+
+TEST(ThrowingBoolTest, ThrowingBool) {
+  ThrowingBool t = true;
+
+  // Test that it's contextually convertible to bool
+  if (t) {  // NOLINT(whitespace/empty_if_body)
+  }
+  EXPECT_TRUE(t);
+
+  TestOp([&]() { (void)!t; });
+}
+
+TEST(ThrowingAllocatorTest, MemoryManagement) {
+  // Just exercise the memory management capabilities under LSan to make sure 
we
+  // don't leak.
+  ThrowingAllocator<int> int_alloc;
+  int* ip = int_alloc.allocate(1);
+  int_alloc.deallocate(ip, 1);
+  int* i_array = int_alloc.allocate(2);
+  int_alloc.deallocate(i_array, 2);
+
+  ThrowingAllocator<ThrowingValue<>> ef_alloc;
+  ThrowingValue<>* efp = ef_alloc.allocate(1);
+  ef_alloc.deallocate(efp, 1);
+  ThrowingValue<>* ef_array = ef_alloc.allocate(2);
+  ef_alloc.deallocate(ef_array, 2);
+}
+
+TEST(ThrowingAllocatorTest, CallsGlobalNew) {
+  ThrowingAllocator<ThrowingValue<>, NoThrow::kNoThrow> nothrow_alloc;
+  ThrowingValue<>* ptr;
+
+  SetCountdown();
+  // This will only throw if ThrowingValue::new is called.
+  ExpectNoThrow([&]() { ptr = nothrow_alloc.allocate(1); });
+  nothrow_alloc.deallocate(ptr, 1);
+
+  UnsetCountdown();
+}
+
+TEST(ThrowingAllocatorTest, ThrowingConstructors) {
+  ThrowingAllocator<int> int_alloc;
+  int* ip = nullptr;
+
+  SetCountdown();
+  EXPECT_THROW(ip = int_alloc.allocate(1), TestException);
+  ExpectNoThrow([&]() { ip = int_alloc.allocate(1); });
+
+  *ip = 1;
+  SetCountdown();
+  EXPECT_THROW(int_alloc.construct(ip, 2), TestException);
+  EXPECT_EQ(*ip, 1);
+  int_alloc.deallocate(ip, 1);
+
+  UnsetCountdown();
+}
+
+TEST(ThrowingAllocatorTest, NonThrowingConstruction) {
+  {
+    ThrowingAllocator<int, NoThrow::kNoThrow> int_alloc;
+    int* ip = nullptr;
+
+    SetCountdown();
+    ExpectNoThrow([&]() { ip = int_alloc.allocate(1); });
+
+    SetCountdown();
+    ExpectNoThrow([&]() { int_alloc.construct(ip, 2); });
+
+    EXPECT_EQ(*ip, 2);
+    int_alloc.deallocate(ip, 1);
+
+    UnsetCountdown();
+  }
+
+  {
+    ThrowingAllocator<int> int_alloc;
+    int* ip = nullptr;
+    ExpectNoThrow([&]() { ip = int_alloc.allocate(1); });
+    ExpectNoThrow([&]() { int_alloc.construct(ip, 2); });
+    EXPECT_EQ(*ip, 2);
+    int_alloc.deallocate(ip, 1);
+  }
+
+  {
+    ThrowingAllocator<ThrowingValue<NoThrow::kIntCtor>, NoThrow::kNoThrow>
+        ef_alloc;
+    ThrowingValue<NoThrow::kIntCtor>* efp;
+
+    SetCountdown();
+    ExpectNoThrow([&]() { efp = ef_alloc.allocate(1); });
+
+    SetCountdown();
+    ExpectNoThrow([&]() { ef_alloc.construct(efp, 2); });
+
+    EXPECT_EQ(efp->Get(), 2);
+    ef_alloc.destroy(efp);
+    ef_alloc.deallocate(efp, 1);
+
+    UnsetCountdown();
+  }
+
+  {
+    ThrowingAllocator<int> a;
+
+    SetCountdown();
+    ExpectNoThrow([&]() { ThrowingAllocator<double> a1 = a; });
+
+    SetCountdown();
+    ExpectNoThrow([&]() { ThrowingAllocator<double> a1 = std::move(a); });
+
+    UnsetCountdown();
+  }
+}
+
+TEST(ThrowingAllocatorTest, ThrowingAllocatorConstruction) {
+  ThrowingAllocator<int> a;
+  TestOp([]() { ThrowingAllocator<int> a; });
+  TestOp([&]() { a.select_on_container_copy_construction(); });
+}
+
+TEST(ThrowingAllocatorTest, State) {
+  ThrowingAllocator<int> a1, a2;
+  EXPECT_NE(a1, a2);
+
+  auto a3 = a1;
+  EXPECT_EQ(a3, a1);
+  int* ip = a1.allocate(1);
+  EXPECT_EQ(a3, a1);
+  a3.deallocate(ip, 1);
+  EXPECT_EQ(a3, a1);
+}
+
+TEST(ThrowingAllocatorTest, InVector) {
+  std::vector<ThrowingValue<>, ThrowingAllocator<ThrowingValue<>>> v;
+  for (int i = 0; i < 20; ++i) v.push_back({});
+  for (int i = 0; i < 20; ++i) v.pop_back();
+}
+
+TEST(ThrowingAllocatorTest, InList) {
+  std::list<ThrowingValue<>, ThrowingAllocator<ThrowingValue<>>> l;
+  for (int i = 0; i < 20; ++i) l.push_back({});
+  for (int i = 0; i < 20; ++i) l.pop_back();
+  for (int i = 0; i < 20; ++i) l.push_front({});
+  for (int i = 0; i < 20; ++i) l.pop_front();
+}
+
+template <typename TesterInstance, typename = void>
+struct NullaryTestValidator : public std::false_type {};
+
+template <typename TesterInstance>
+struct NullaryTestValidator<
+    TesterInstance,
+    absl::void_t<decltype(std::declval<TesterInstance>().Test())>>
+    : public std::true_type {};
+
+template <typename TesterInstance>
+bool HasNullaryTest(const TesterInstance&) {
+  return NullaryTestValidator<TesterInstance>::value;
+}
+
+void DummyOp(void*) {}
+
+template <typename TesterInstance, typename = void>
+struct UnaryTestValidator : public std::false_type {};
+
+template <typename TesterInstance>
+struct UnaryTestValidator<
+    TesterInstance,
+    absl::void_t<decltype(std::declval<TesterInstance>().Test(DummyOp))>>
+    : public std::true_type {};
+
+template <typename TesterInstance>
+bool HasUnaryTest(const TesterInstance&) {
+  return UnaryTestValidator<TesterInstance>::value;
+}
+
+TEST(ExceptionSafetyTesterTest, IncompleteTypesAreNotTestable) {
+  using T = exceptions_internal::UninitializedT;
+  auto op = [](T* t) {};
+  auto inv = [](T*) { return testing::AssertionSuccess(); };
+  auto fac = []() { return absl::make_unique<T>(); };
+
+  // Test that providing operation and inveriants still does not allow for the
+  // the invocation of .Test() and .Test(op) because it lacks a factory
+  auto without_fac =
+      absl::MakeExceptionSafetyTester().WithOperation(op).WithInvariants(
+          inv, absl::strong_guarantee);
+  EXPECT_FALSE(HasNullaryTest(without_fac));
+  EXPECT_FALSE(HasUnaryTest(without_fac));
+
+  // Test that providing invariants and factory allows the invocation of
+  // .Test(op) but does not allow for .Test() because it lacks an operation
+  auto without_op = absl::MakeExceptionSafetyTester()
+                        .WithInvariants(inv, absl::strong_guarantee)
+                        .WithFactory(fac);
+  EXPECT_FALSE(HasNullaryTest(without_op));
+  EXPECT_TRUE(HasUnaryTest(without_op));
+
+  // Test that providing operation and factory still does not allow for the
+  // the invocation of .Test() and .Test(op) because it lacks invariants
+  auto without_inv =
+      absl::MakeExceptionSafetyTester().WithOperation(op).WithFactory(fac);
+  EXPECT_FALSE(HasNullaryTest(without_inv));
+  EXPECT_FALSE(HasUnaryTest(without_inv));
+}
+
+struct ExampleStruct {};
+
+std::unique_ptr<ExampleStruct> ExampleFunctionFactory() {
+  return absl::make_unique<ExampleStruct>();
+}
+
+void ExampleFunctionOperation(ExampleStruct*) {}
+
+testing::AssertionResult ExampleFunctionInvariant(ExampleStruct*) {
+  return testing::AssertionSuccess();
+}
+
+struct {
+  std::unique_ptr<ExampleStruct> operator()() const {
+    return ExampleFunctionFactory();
+  }
+} example_struct_factory;
+
+struct {
+  void operator()(ExampleStruct*) const {}
+} example_struct_operation;
+
+struct {
+  testing::AssertionResult operator()(ExampleStruct* example_struct) const {
+    return ExampleFunctionInvariant(example_struct);
+  }
+} example_struct_invariant;
+
+auto example_lambda_factory = []() { return ExampleFunctionFactory(); };
+
+auto example_lambda_operation = [](ExampleStruct*) {};
+
+auto example_lambda_invariant = [](ExampleStruct* example_struct) {
+  return ExampleFunctionInvariant(example_struct);
+};
+
+// Testing that function references, pointers, structs with operator() and
+// lambdas can all be used with ExceptionSafetyTester
+TEST(ExceptionSafetyTesterTest, MixedFunctionTypes) {
+  // function reference
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(ExampleFunctionFactory)
+                  .WithOperation(ExampleFunctionOperation)
+                  .WithInvariants(ExampleFunctionInvariant)
+                  .Test());
+
+  // function pointer
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(&ExampleFunctionFactory)
+                  .WithOperation(&ExampleFunctionOperation)
+                  .WithInvariants(&ExampleFunctionInvariant)
+                  .Test());
+
+  // struct
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(example_struct_factory)
+                  .WithOperation(example_struct_operation)
+                  .WithInvariants(example_struct_invariant)
+                  .Test());
+
+  // lambda
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(example_lambda_factory)
+                  .WithOperation(example_lambda_operation)
+                  .WithInvariants(example_lambda_invariant)
+                  .Test());
+}
+
+struct NonNegative {
+  bool operator==(const NonNegative& other) const { return i == other.i; }
+  int i;
+};
+
+testing::AssertionResult CheckNonNegativeInvariants(NonNegative* g) {
+  if (g->i >= 0) {
+    return testing::AssertionSuccess();
+  }
+  return testing::AssertionFailure()
+         << "i should be non-negative but is " << g->i;
+}
+
+struct {
+  template <typename T>
+  void operator()(T* t) const {
+    (*t)();
+  }
+} invoker;
+
+auto tester =
+    absl::MakeExceptionSafetyTester().WithOperation(invoker).WithInvariants(
+        CheckNonNegativeInvariants);
+auto strong_tester = tester.WithInvariants(absl::strong_guarantee);
+
+struct FailsBasicGuarantee : public NonNegative {
+  void operator()() {
+    --i;
+    ThrowingValue<> bomb;
+    ++i;
+  }
+};
+
+TEST(ExceptionCheckTest, BasicGuaranteeFailure) {
+  EXPECT_FALSE(tester.WithInitialValue(FailsBasicGuarantee{}).Test());
+}
+
+struct FollowsBasicGuarantee : public NonNegative {
+  void operator()() {
+    ++i;
+    ThrowingValue<> bomb;
+  }
+};
+
+TEST(ExceptionCheckTest, BasicGuarantee) {
+  EXPECT_TRUE(tester.WithInitialValue(FollowsBasicGuarantee{}).Test());
+}
+
+TEST(ExceptionCheckTest, StrongGuaranteeFailure) {
+  EXPECT_FALSE(strong_tester.WithInitialValue(FailsBasicGuarantee{}).Test());
+  EXPECT_FALSE(strong_tester.WithInitialValue(FollowsBasicGuarantee{}).Test());
+}
+
+struct BasicGuaranteeWithExtraInvariants : public NonNegative {
+  // After operator(), i is incremented.  If operator() throws, i is set to 
9999
+  void operator()() {
+    int old_i = i;
+    i = kExceptionSentinel;
+    ThrowingValue<> bomb;
+    i = ++old_i;
+  }
+
+  static constexpr int kExceptionSentinel = 9999;
+};
+constexpr int BasicGuaranteeWithExtraInvariants::kExceptionSentinel;
+
+TEST(ExceptionCheckTest, BasicGuaranteeWithInvariants) {
+  auto tester_with_val =
+      tester.WithInitialValue(BasicGuaranteeWithExtraInvariants{});
+  EXPECT_TRUE(tester_with_val.Test());
+  EXPECT_TRUE(
+      tester_with_val
+          .WithInvariants([](BasicGuaranteeWithExtraInvariants* w) {
+            if (w->i == BasicGuaranteeWithExtraInvariants::kExceptionSentinel) 
{
+              return testing::AssertionSuccess();
+            }
+            return testing::AssertionFailure()
+                   << "i should be "
+                   << BasicGuaranteeWithExtraInvariants::kExceptionSentinel
+                   << ", but is " << w->i;
+          })
+          .Test());
+}
+
+struct FollowsStrongGuarantee : public NonNegative {
+  void operator()() { ThrowingValue<> bomb; }
+};
+
+TEST(ExceptionCheckTest, StrongGuarantee) {
+  EXPECT_TRUE(tester.WithInitialValue(FollowsStrongGuarantee{}).Test());
+  EXPECT_TRUE(strong_tester.WithInitialValue(FollowsStrongGuarantee{}).Test());
+}
+
+struct HasReset : public NonNegative {
+  void operator()() {
+    i = -1;
+    ThrowingValue<> bomb;
+    i = 1;
+  }
+
+  void reset() { i = 0; }
+};
+
+testing::AssertionResult CheckHasResetInvariants(HasReset* h) {
+  h->reset();
+  return testing::AssertionResult(h->i == 0);
+}
+
+TEST(ExceptionCheckTest, ModifyingChecker) {
+  auto set_to_1000 = [](FollowsBasicGuarantee* g) {
+    g->i = 1000;
+    return testing::AssertionSuccess();
+  };
+  auto is_1000 = [](FollowsBasicGuarantee* g) {
+    return testing::AssertionResult(g->i == 1000);
+  };
+  auto increment = [](FollowsStrongGuarantee* g) {
+    ++g->i;
+    return testing::AssertionSuccess();
+  };
+
+  EXPECT_FALSE(tester.WithInitialValue(FollowsBasicGuarantee{})
+                   .WithInvariants(set_to_1000, is_1000)
+                   .Test());
+  EXPECT_TRUE(strong_tester.WithInitialValue(FollowsStrongGuarantee{})
+                  .WithInvariants(increment)
+                  .Test());
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithInitialValue(HasReset{})
+                  .WithInvariants(CheckHasResetInvariants)
+                  .Test(invoker));
+}
+
+struct NonCopyable : public NonNegative {
+  NonCopyable(const NonCopyable&) = delete;
+  NonCopyable() : NonNegative{0} {}
+
+  void operator()() { ThrowingValue<> bomb; }
+};
+
+TEST(ExceptionCheckTest, NonCopyable) {
+  auto factory = []() { return absl::make_unique<NonCopyable>(); };
+  EXPECT_TRUE(tester.WithFactory(factory).Test());
+  EXPECT_TRUE(strong_tester.WithFactory(factory).Test());
+}
+
+struct NonEqualityComparable : public NonNegative {
+  void operator()() { ThrowingValue<> bomb; }
+
+  void ModifyOnThrow() {
+    ++i;
+    ThrowingValue<> bomb;
+    static_cast<void>(bomb);
+    --i;
+  }
+};
+
+TEST(ExceptionCheckTest, NonEqualityComparable) {
+  auto nec_is_strong = [](NonEqualityComparable* nec) {
+    return testing::AssertionResult(nec->i == NonEqualityComparable().i);
+  };
+  auto strong_nec_tester = tester.WithInitialValue(NonEqualityComparable{})
+                               .WithInvariants(nec_is_strong);
+
+  EXPECT_TRUE(strong_nec_tester.Test());
+  EXPECT_FALSE(strong_nec_tester.Test(
+      [](NonEqualityComparable* n) { n->ModifyOnThrow(); }));
+}
+
+template <typename T>
+struct ExhaustivenessTester {
+  void operator()() {
+    successes |= 1;
+    T b1;
+    static_cast<void>(b1);
+    successes |= (1 << 1);
+    T b2;
+    static_cast<void>(b2);
+    successes |= (1 << 2);
+    T b3;
+    static_cast<void>(b3);
+    successes |= (1 << 3);
+  }
+
+  bool operator==(const ExhaustivenessTester<ThrowingValue<>>&) const {
+    return true;
+  }
+
+  static unsigned char successes;
+};
+
+struct {
+  template <typename T>
+  testing::AssertionResult operator()(ExhaustivenessTester<T>*) const {
+    return testing::AssertionSuccess();
+  }
+} CheckExhaustivenessTesterInvariants;
+
+template <typename T>
+unsigned char ExhaustivenessTester<T>::successes = 0;
+
+TEST(ExceptionCheckTest, Exhaustiveness) {
+  auto exhaust_tester = absl::MakeExceptionSafetyTester()
+                            
.WithInvariants(CheckExhaustivenessTesterInvariants)
+                            .WithOperation(invoker);
+
+  EXPECT_TRUE(
+      exhaust_tester.WithInitialValue(ExhaustivenessTester<int>{}).Test());
+  EXPECT_EQ(ExhaustivenessTester<int>::successes, 0xF);
+
+  EXPECT_TRUE(
+      exhaust_tester.WithInitialValue(ExhaustivenessTester<ThrowingValue<>>{})
+          .WithInvariants(absl::strong_guarantee)
+          .Test());
+  EXPECT_EQ(ExhaustivenessTester<ThrowingValue<>>::successes, 0xF);
+}
+
+struct LeaksIfCtorThrows : private exceptions_internal::TrackedObject {
+  LeaksIfCtorThrows() : TrackedObject(ABSL_PRETTY_FUNCTION) {
+    ++counter;
+    ThrowingValue<> v;
+    static_cast<void>(v);
+    --counter;
+  }
+  LeaksIfCtorThrows(const LeaksIfCtorThrows&) noexcept
+      : TrackedObject(ABSL_PRETTY_FUNCTION) {}
+  static int counter;
+};
+int LeaksIfCtorThrows::counter = 0;
+
+TEST(ExceptionCheckTest, TestLeakyCtor) {
+  absl::TestThrowingCtor<LeaksIfCtorThrows>();
+  EXPECT_EQ(LeaksIfCtorThrows::counter, 1);
+  LeaksIfCtorThrows::counter = 0;
+}
+
+struct Tracked : private exceptions_internal::TrackedObject {
+  Tracked() : TrackedObject(ABSL_PRETTY_FUNCTION) {}
+};
+
+TEST(ConstructorTrackerTest, CreatedBefore) {
+  Tracked a, b, c;
+  exceptions_internal::ConstructorTracker ct(exceptions_internal::countdown);
+}
+
+TEST(ConstructorTrackerTest, CreatedAfter) {
+  exceptions_internal::ConstructorTracker ct(exceptions_internal::countdown);
+  Tracked a, b, c;
+}
+
+TEST(ConstructorTrackerTest, NotDestroyedAfter) {
+  absl::aligned_storage_t<sizeof(Tracked), alignof(Tracked)> storage;
+  EXPECT_NONFATAL_FAILURE(
+      {
+        exceptions_internal::ConstructorTracker ct(
+            exceptions_internal::countdown);
+        new (&storage) Tracked;
+      },
+      "not destroyed");
+
+  // Manual destruction of the Tracked instance is not required because
+  // ~ConstructorTracker() handles that automatically when a leak is found
+}
+
+TEST(ConstructorTrackerTest, DestroyedTwice) {
+  EXPECT_NONFATAL_FAILURE(
+      {
+        Tracked t;
+        t.~Tracked();
+      },
+      "destroyed improperly");
+}
+
+TEST(ConstructorTrackerTest, ConstructedTwice) {
+  absl::aligned_storage_t<sizeof(Tracked), alignof(Tracked)> storage;
+  EXPECT_NONFATAL_FAILURE(
+      {
+        new (&storage) Tracked;
+        new (&storage) Tracked;
+      },
+      "re-constructed");
+  reinterpret_cast<Tracked*>(&storage)->~Tracked();
+}
+
+TEST(ThrowingValueTraitsTest, RelationalOperators) {
+  ThrowingValue<> a, b;
+  EXPECT_TRUE((std::is_convertible<decltype(a == b), bool>::value));
+  EXPECT_TRUE((std::is_convertible<decltype(a != b), bool>::value));
+  EXPECT_TRUE((std::is_convertible<decltype(a < b), bool>::value));
+  EXPECT_TRUE((std::is_convertible<decltype(a <= b), bool>::value));
+  EXPECT_TRUE((std::is_convertible<decltype(a > b), bool>::value));
+  EXPECT_TRUE((std::is_convertible<decltype(a >= b), bool>::value));
+}
+
+TEST(ThrowingAllocatorTraitsTest, Assignablility) {
+  EXPECT_TRUE(std::is_move_assignable<ThrowingAllocator<int>>::value);
+  EXPECT_TRUE(std::is_copy_assignable<ThrowingAllocator<int>>::value);
+  EXPECT_TRUE(std::is_nothrow_move_assignable<ThrowingAllocator<int>>::value);
+  EXPECT_TRUE(std::is_nothrow_copy_assignable<ThrowingAllocator<int>>::value);
+}
+
+}  // namespace
+}  // namespace absl

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test.cc
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test.cc 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test.cc
new file mode 100644
index 0000000..5499189
--- /dev/null
+++ 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test.cc
@@ -0,0 +1,62 @@
+// 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
+//
+//      http://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 <type_traits>
+
+#include "absl/base/internal/inline_variable.h"
+#include "absl/base/internal/inline_variable_testing.h"
+
+#include "gtest/gtest.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+namespace {
+
+TEST(InlineVariableTest, Constexpr) {
+  static_assert(inline_variable_foo.value == 5, "");
+  static_assert(other_inline_variable_foo.value == 5, "");
+  static_assert(inline_variable_int == 5, "");
+  static_assert(other_inline_variable_int == 5, "");
+}
+
+TEST(InlineVariableTest, DefaultConstructedIdentityEquality) {
+  EXPECT_EQ(get_foo_a().value, 5);
+  EXPECT_EQ(get_foo_b().value, 5);
+  EXPECT_EQ(&get_foo_a(), &get_foo_b());
+}
+
+TEST(InlineVariableTest, DefaultConstructedIdentityInequality) {
+  EXPECT_NE(&inline_variable_foo, &other_inline_variable_foo);
+}
+
+TEST(InlineVariableTest, InitializedIdentityEquality) {
+  EXPECT_EQ(get_int_a(), 5);
+  EXPECT_EQ(get_int_b(), 5);
+  EXPECT_EQ(&get_int_a(), &get_int_b());
+}
+
+TEST(InlineVariableTest, InitializedIdentityInequality) {
+  EXPECT_NE(&inline_variable_int, &other_inline_variable_int);
+}
+
+TEST(InlineVariableTest, FunPtrType) {
+  static_assert(
+      std::is_same<void(*)(),
+                   std::decay<decltype(inline_variable_fun_ptr)>::type>::value,
+      "");
+}
+
+}  // namespace
+}  // namespace inline_variable_testing_internal
+}  // namespace absl

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_a.cc
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_a.cc 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_a.cc
new file mode 100644
index 0000000..a3bf3b6
--- /dev/null
+++ 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_a.cc
@@ -0,0 +1,25 @@
+// 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
+//
+//      http://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/inline_variable_testing.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+
+const Foo& get_foo_a() { return inline_variable_foo; }
+
+const int& get_int_a() { return inline_variable_int; }
+
+}  // namespace inline_variable_testing_internal
+}  // namespace absl

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_b.cc
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_b.cc 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_b.cc
new file mode 100644
index 0000000..b4b9393
--- /dev/null
+++ 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/inline_variable_test_b.cc
@@ -0,0 +1,25 @@
+// 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
+//
+//      http://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/inline_variable_testing.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+
+const Foo& get_foo_b() { return inline_variable_foo; }
+
+const int& get_int_b() { return inline_variable_int; }
+
+}  // namespace inline_variable_testing_internal
+}  // namespace absl

http://git-wip-us.apache.org/repos/asf/marmotta/blob/0eb556da/libraries/ostrich/backend/3rdparty/abseil/absl/base/internal/atomic_hook.h
----------------------------------------------------------------------
diff --git 
a/libraries/ostrich/backend/3rdparty/abseil/absl/base/internal/atomic_hook.h 
b/libraries/ostrich/backend/3rdparty/abseil/absl/base/internal/atomic_hook.h
new file mode 100644
index 0000000..47d4013
--- /dev/null
+++ b/libraries/ostrich/backend/3rdparty/abseil/absl/base/internal/atomic_hook.h
@@ -0,0 +1,150 @@
+// 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
+//
+//      http://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_ATOMIC_HOOK_H_
+#define ABSL_BASE_INTERNAL_ATOMIC_HOOK_H_
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <utility>
+
+namespace absl {
+namespace base_internal {
+
+template <typename T>
+class AtomicHook;
+
+// AtomicHook is a helper class, templatized on a raw function pointer type, 
for
+// implementing Abseil customization hooks.  It is a callable object that
+// dispatches to the registered hook, or performs a no-op (and returns a 
default
+// constructed object) if no hook has been registered.
+//
+// Reads and writes guarantee memory_order_acquire/memory_order_release
+// semantics.
+template <typename ReturnType, typename... Args>
+class AtomicHook<ReturnType (*)(Args...)> {
+ public:
+  using FnPtr = ReturnType (*)(Args...);
+
+  constexpr AtomicHook() : hook_(kInitialValue) {}
+
+  // Stores the provided function pointer as the value for this hook.
+  //
+  // This is intended to be called once.  Multiple calls are legal only if the
+  // same function pointer is provided for each call.  The store is implemented
+  // as a memory_order_release operation, and read accesses are implemented as
+  // memory_order_acquire.
+  void Store(FnPtr fn) {
+    bool success = DoStore(fn);
+    static_cast<void>(success);
+    assert(success);
+  }
+
+  // Invokes the registered callback.  If no callback has yet been registered, 
a
+  // default-constructed object of the appropriate type is returned instead.
+  template <typename... CallArgs>
+  ReturnType operator()(CallArgs&&... args) const {
+    return DoLoad()(std::forward<CallArgs>(args)...);
+  }
+
+  // Returns the registered callback, or nullptr if none has been registered.
+  // Useful if client code needs to conditionalize behavior based on whether a
+  // callback was registered.
+  //
+  // Note that atomic_hook.Load()() and atomic_hook() have different semantics:
+  // operator()() will perform a no-op if no callback was registered, while
+  // Load()() will dereference a null function pointer.  Prefer operator()() to
+  // Load()() unless you must conditionalize behavior on whether a hook was
+  // registered.
+  FnPtr Load() const {
+    FnPtr ptr = DoLoad();
+    return (ptr == DummyFunction) ? nullptr : ptr;
+  }
+
+ private:
+  static ReturnType DummyFunction(Args...) {
+    return ReturnType();
+  }
+
+  // Current versions of MSVC (as of September 2017) have a broken
+  // implementation of std::atomic<T*>:  Its constructor attempts to do the
+  // equivalent of a reinterpret_cast in a constexpr context, which is not
+  // allowed.
+  //
+  // This causes an issue when building with LLVM under Windows.  To avoid 
this,
+  // we use a less-efficient, intptr_t-based implementation on Windows.
+
+#ifdef _MSC_FULL_VER
+#define ABSL_HAVE_WORKING_ATOMIC_POINTER 0
+#else
+#define ABSL_HAVE_WORKING_ATOMIC_POINTER 1
+#endif
+
+#if ABSL_HAVE_WORKING_ATOMIC_POINTER
+  static constexpr FnPtr kInitialValue = &DummyFunction;
+
+  // Return the stored value, or DummyFunction if no value has been stored.
+  FnPtr DoLoad() const { return hook_.load(std::memory_order_acquire); }
+
+  // Store the given value.  Returns false if a different value was already
+  // stored to this object.
+  bool DoStore(FnPtr fn) {
+    assert(fn);
+    FnPtr expected = DummyFunction;
+    hook_.compare_exchange_strong(expected, fn, std::memory_order_acq_rel,
+                                  std::memory_order_acquire);
+    const bool store_succeeded = (expected == DummyFunction);
+    const bool same_value_already_stored = (expected == fn);
+    return store_succeeded || same_value_already_stored;
+  }
+
+  std::atomic<FnPtr> hook_;
+#else  // !ABSL_HAVE_WORKING_ATOMIC_POINTER
+  // Use a sentinel value unlikely to be the address of an actual function.
+  static constexpr intptr_t kInitialValue = 0;
+
+  static_assert(sizeof(intptr_t) >= sizeof(FnPtr),
+                "intptr_t can't contain a function pointer");
+
+  FnPtr DoLoad() const {
+    const intptr_t value = hook_.load(std::memory_order_acquire);
+    if (value == 0) {
+      return DummyFunction;
+    }
+    return reinterpret_cast<FnPtr>(value);
+  }
+
+  bool DoStore(FnPtr fn) {
+    assert(fn);
+    const auto value = reinterpret_cast<intptr_t>(fn);
+    intptr_t expected = 0;
+    hook_.compare_exchange_strong(expected, value, std::memory_order_acq_rel,
+                                  std::memory_order_acquire);
+    const bool store_succeeded = (expected == 0);
+    const bool same_value_already_stored = (expected == value);
+    return store_succeeded || same_value_already_stored;
+  }
+
+  std::atomic<intptr_t> hook_;
+#endif
+};
+
+#undef ABSL_HAVE_WORKING_ATOMIC_POINTER
+
+}  // namespace base_internal
+}  // namespace absl
+
+#endif  // ABSL_BASE_INTERNAL_ATOMIC_HOOK_H_

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