Export of internal Abseil changes

--
2f49cb9009386bc67bf54a2908c8720b749c8b7f by Greg Falcon <gfalcon@google.com>:

docs: fix typo

Import of https://github.com/abseil/abseil-cpp/pull/397

PiperOrigin-RevId: 277504420

--
f2bed362c1c12d3fa9c22d11f2b918668e8c37b7 by Abseil Team <absl-team@google.com>:

Avoid our is_[copy/move]_assignable workarounds in MSVC 19.20 and on, since that release introduces a regression that breaks our workaround. We should ideally use the std forms in more cases, but branching when our workarounds fail is simpler to maintain.

PiperOrigin-RevId: 277502334

--
e33de894ffd49848b9e088f59acc9743d1661948 by Derek Mauro <dmauro@google.com>:

Update rules_cc version. The mirror.bazel.build URL does not exist
(cache expiration?)

PiperOrigin-RevId: 277498394

--
b23757b0747c64634d2d701433782c969effef19 by Abseil Team <absl-team@google.com>:

Fix https://github.com/abseil/abseil-cpp/issues/394.

PiperOrigin-RevId: 277491405

--
54c75b8b29813531c52d67cf0ba7063baae4a4f3 by Abseil Team <absl-team@google.com>:

Fix comment typos: waker => waiter.

PiperOrigin-RevId: 277376952

--
874eeaa3b3af808fc88b6355245f643674f5e36e by Abseil Team <absl-team@google.com>:

Don't use atomic ops on waiter and wakeup counts in CONDVAR waiter mode.

Just guard the waiter and wakeup counts with the mutex. This eliminates the
race.

Also fix a typo in the error message for pthread_cond_timedwait.

PiperOrigin-RevId: 277366017

--
ce8c9a63109214519b5a7eaecef2c663c4d566df by Greg Falcon <gfalcon@google.com>:

Implement the config options for our four main C++ forward compatibility types.

These options control whether the names `any`, `optional`, `string_view`, and `variant` in namespace `absl` are aliases to the corresponding C++17 types in namespace `std`.  By default, we continue to auto-detect the configuration of the compiler being run.

These options are not intended to be modified on the command line (as -D flags, say).  Instead, the options.h file can be modified by distributors of Abseil (e.g., binary packagers, maintainers of local copies of Abseil, etc.)

Changing options will change Abseil in an ODR sense.  Any program must only link in a single version of Abseil.  Linking libraries that use Abseil configured with different options is an error: there is no ABI compatibility guarantee when linking different configurations, even if the Abseil versions used are otherwise exactly identical.

PiperOrigin-RevId: 277364298

--
5ed3ad42ae43a05862070f92f9ffd07f5c1f2b81 by Chris Kennelly <ckennelly@google.com>:

Suppress -Wimplicit-int-float-conversion.

On recent builds of Clang, this is an error/warning.

PiperOrigin-RevId: 277346168

--
9b9b0055243c705189bb27d912e6d45a7789cdee by Eric Fiselier <ericwf@google.com>:

Allow building Abseil as a shared library with CMake.

By default CMake's `add_library` creates the target as a static
library. However, users can override the default using the builtin
CMake option -DBUILD_SHARED_LIBS=ON.

This changes Abseil's CMake to respect this configuration option
by removing the explicit `STATIC` in our usages of `add_library`.

PiperOrigin-RevId: 277337753

--
63a8b7b8ede3a9d851916929d6b8537f4f2508ca by Abseil Team <absl-team@google.com>:

Improve AlphaNum Hex performance by using absl::numbers_internal::FastHexToBufferZeroPad16.

PiperOrigin-RevId: 277318108

--
dd047f7e92032682d94b27732df0e4d0670e24a4 by CJ Johnson <johnsoncj@google.com>:

Internal change

PiperOrigin-RevId: 277316913

--
d19ee7074929fed08973cc5b40a844573ce1e0a6 by Abseil Team <absl-team@google.com>:

Handle invoking [[nodiscard]] functions correctly in our tests.

PiperOrigin-RevId: 277301500

--
5373f3737894ba9b8481e95e5f58c7957c00d26a by Chris Kennelly <ckennelly@google.com>:

For internal reasons, loosen visibility restrictions of `//absl/base:malloc_internal`.

As an internal-namespace interface, this module remains unsupported.  We
reserve the right to change, delete, or re-restrict visibility to this target
at any time.

PiperOrigin-RevId: 277118689

--
44e4f6655e05393a375d09b3625c192b1fde5909 by Abseil Team <absl-team@google.com>:

Fix error in example civil day comment.

PiperOrigin-RevId: 277103315

--
7657392b4ce48469106f11cdb952a0bc76a28df3 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 277056076

--
c75bda76f40b01fa249b75b5a70c1f5907e56c76 by Abseil Team <absl-team@google.com>:

Suppress lifetime constant-initialization tests when building with MSVC versions > 19.0.

These are broken due to non-compliant initialization order in these versions:
https://developercommunity.visualstudio.com/content/problem/336946/class-with-constexpr-constructor-not-using-static.html
We don't know when Microsoft will fix this bug.

PiperOrigin-RevId: 277049770

--
16c3b9bf2a1796efa57f97b00bcd6227fbccca1f by Matt Calabrese <calabrese@google.com>:

Avoid our is_[copy/move]_assignable workarounds in MSVC 19.20 and on, since that release introduces a regression that breaks our workaround. We should ideally use the std forms in more cases, but branching when our workarounds fail is simpler to maintain.

PiperOrigin-RevId: 277048670

--
e91003fa3ee6026d9b80624a23fc144fa5d74810 by Chris Kennelly <ckennelly@google.com>:

Fix -Wimplicit-int-float-conversion warning in latest clang

PiperOrigin-RevId: 276771618

--
53087ca6603e86ad815f3dd9ab795cc0f79792c1 by Andy Soffer <asoffer@google.com>:

Add documentation on absl::SNPrintF.

PiperOrigin-RevId: 276694032

--
a9426af8cbd4c3a8f9053e7446c821852e41ff61 by Jorg Brown <jorg@google.com>:

Stop including kern/OSByteOrder.h in order to support __APPLE__

Apple compiles with clang now anyway, and clang has support for the
built-in compiler swap functions that are much faster than any function call to
the OS.

PiperOrigin-RevId: 276625231

--
df974be5aa5b4dc1b09c356cb8816edfc7867e63 by Jorg Brown <jorg@google.com>:

Fix the build for Android x86-64 builds, where __SSE4_2__ is defined but
_bswap64 is not.

PiperOrigin-RevId: 276542642

--
d99dc092b3a5ad17643005e55f3b3cb6b9187ccc by Jorg Brown <jorg@google.com>:

Remove a byteswap from the non-SSE path of FastHexToBufferZeroPad16

Remove the need for including absl/base/internal/endian.h from the SSE case
(since if we have the Intel SSE intrinsics, then clearly we also have the
Intel Byte-Swap intrinsics.)

PiperOrigin-RevId: 276532608

--
d67b106dc930d8558810ae3983613bb2ab1e0d36 by Abseil Team <absl-team@google.com>:

Use explicit static_cast<double> for int64_t to double conversion

This uses an explicit static_cast<double>() in the int64_t to double comparisons in duration.cc's SafeAddRepHi. This satisfies clang's -Wimplicit-int-to-float-conversion warning (with https://reviews.llvm.org/D64666). This may also make it easier for humans to realize that the comparison is happening between two floating point double precision values.  It should have no impact on the behavior or generated code.
Tested:
No behavior change
PiperOrigin-RevId: 276529211
GitOrigin-RevId: 2f49cb9009386bc67bf54a2908c8720b749c8b7f
Change-Id: I71e0781893ce219960b8290d54b20532779cb0ff

5 files changed, 254 insertions, 9 deletions

diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index ffeca63..6fc712d 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -87,6 +87,7 @@ cc_library(
     name = "config",
     hdrs = [
         "config.h",
+        "options.h",
         "policy_checks.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
@@ -137,7 +138,7 @@ cc_library(
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
     visibility = [
-        "//absl:__subpackages__",
+        "//visibility:public",
     ],
     deps = [
         ":base",
diff --git a/absl/base/CMakeLists.txt b/absl/base/CMakeLists.txt
index 2698213..9550cdb 100644
--- a/absl/base/CMakeLists.txt
+++ b/absl/base/CMakeLists.txt
@@ -75,6 +75,7 @@ absl_cc_library(
     config
   HDRS
     "config.h"
+    "options.h"
     "policy_checks.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
diff --git a/absl/base/config.h b/absl/base/config.h
index 24851fa..46a84f1 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -63,6 +63,7 @@
 #include <TargetConditionals.h>
 #endif
 
+#include "absl/base/options.h"
 #include "absl/base/policy_checks.h"
 
 // -----------------------------------------------------------------------------
@@ -468,6 +469,68 @@
 #define ABSL_HAVE_STD_STRING_VIEW 1
 #endif
 
+// ABSL_USES_STD_ANY
+//
+// Indicates whether absl::any is an alias for std::any.
+#if !defined(ABSL_OPTION_USE_STD_ANY)
+#error options.h is misconfigured.
+#elif ABSL_OPTION_USE_STD_ANY == 0 || \
+    (ABSL_OPTION_USE_STD_ANY == 2 && !defined(ABSL_HAVE_STD_ANY))
+#undef ABSL_USES_STD_ANY
+#elif ABSL_OPTION_USE_STD_ANY == 1 || \
+    (ABSL_OPTION_USE_STD_ANY == 2 && defined(ABSL_HAVE_STD_ANY))
+#define ABSL_USES_STD_ANY 1
+#else
+#error options.h is misconfigured.
+#endif
+
+// ABSL_USES_STD_OPTIONAL
+//
+// Indicates whether absl::optional is an alias for std::optional.
+#if !defined(ABSL_OPTION_USE_STD_OPTIONAL)
+#error options.h is misconfigured.
+#elif ABSL_OPTION_USE_STD_OPTIONAL == 0 || \
+    (ABSL_OPTION_USE_STD_OPTIONAL == 2 && !defined(ABSL_HAVE_STD_OPTIONAL))
+#undef ABSL_USES_STD_OPTIONAL
+#elif ABSL_OPTION_USE_STD_OPTIONAL == 1 || \
+    (ABSL_OPTION_USE_STD_OPTIONAL == 2 && defined(ABSL_HAVE_STD_OPTIONAL))
+#define ABSL_USES_STD_OPTIONAL 1
+#else
+#error options.h is misconfigured.
+#endif
+
+// ABSL_USES_STD_VARIANT
+//
+// Indicates whether absl::variant is an alias for std::variant.
+#if !defined(ABSL_OPTION_USE_STD_VARIANT)
+#error options.h is misconfigured.
+#elif ABSL_OPTION_USE_STD_VARIANT == 0 || \
+    (ABSL_OPTION_USE_STD_VARIANT == 2 && !defined(ABSL_HAVE_STD_VARIANT))
+#undef ABSL_USES_STD_VARIANT
+#elif ABSL_OPTION_USE_STD_VARIANT == 1 || \
+    (ABSL_OPTION_USE_STD_VARIANT == 2 && defined(ABSL_HAVE_STD_VARIANT))
+#define ABSL_USES_STD_VARIANT 1
+#else
+#error options.h is misconfigured.
+#endif
+
+// ABSL_USES_STD_STRING_VIEW
+//
+// Indicates whether absl::string_view is an alias for std::string_view.
+#if !defined(ABSL_OPTION_USE_STD_STRING_VIEW)
+#error options.h is misconfigured.
+#elif ABSL_OPTION_USE_STD_STRING_VIEW == 0 || \
+    (ABSL_OPTION_USE_STD_STRING_VIEW == 2 &&  \
+     !defined(ABSL_HAVE_STD_STRING_VIEW))
+#undef ABSL_USES_STD_STRING_VIEW
+#elif ABSL_OPTION_USE_STD_STRING_VIEW == 1 || \
+    (ABSL_OPTION_USE_STD_STRING_VIEW == 2 &&  \
+     defined(ABSL_HAVE_STD_STRING_VIEW))
+#define ABSL_USES_STD_STRING_VIEW 1
+#else
+#error options.h is misconfigured.
+#endif
+
 // In debug mode, MSVC 2017's std::variant throws a EXCEPTION_ACCESS_VIOLATION
 // SEH exception from emplace for variant<SomeStruct> when constructing the
 // struct can throw. This defeats some of variant_test and
diff --git a/absl/base/internal/endian.h b/absl/base/internal/endian.h
index b43c9a4..8233cb5 100644
--- a/absl/base/internal/endian.h
+++ b/absl/base/internal/endian.h
@@ -19,9 +19,6 @@
 // The following guarantees declaration of the byte swap functions
 #ifdef _MSC_VER
 #include <stdlib.h>  // NOLINT(build/include)
-#elif defined(__APPLE__)
-// macOS / Darwin features
-#include <libkern/OSByteOrder.h>
 #elif defined(__FreeBSD__)
 #include <sys/endian.h>
 #elif defined(__GLIBC__)
@@ -63,11 +60,6 @@ inline uint16_t gbswap_16(uint16_t host_int) {
   return _byteswap_ushort(host_int);
 }
 
-#elif defined(__APPLE__)
-inline uint64_t gbswap_64(uint64_t host_int) { return OSSwapInt16(host_int); }
-inline uint32_t gbswap_32(uint32_t host_int) { return OSSwapInt32(host_int); }
-inline uint16_t gbswap_16(uint16_t host_int) { return OSSwapInt64(host_int); }
-
 #else
 inline uint64_t gbswap_64(uint64_t host_int) {
 #if defined(__GNUC__) && defined(__x86_64__) && !defined(__APPLE__)
diff --git a/absl/base/options.h b/absl/base/options.h
new file mode 100644
index 0000000..3961e63
--- /dev/null
+++ b/absl/base/options.h
@@ -0,0 +1,188 @@
+#ifndef ABSL_BASE_OPTIONS_H_
+#define ABSL_BASE_OPTIONS_H_
+
+// Copyright 2019 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.
+//
+// -----------------------------------------------------------------------------
+// File: options.h
+// -----------------------------------------------------------------------------
+//
+// This file contains Abseil configuration options for setting specific
+// implementations instead of letting Abseil determine which implementation to
+// use at compile-time. Setting these options may be useful for package or build
+// managers who wish to guarantee ABI stability within binary builds (which are
+// otherwise difficult to enforce).
+//
+// *** IMPORTANT NOTICE FOR PACKAGE MANAGERS:  It is important that
+// maintainers of package managers who wish to package Abseil read and
+// understand this file! ***
+//
+// Abseil contains a number of possible configuration endpoints, based on
+// parameters such as the detected platform, language version, or command-line
+// flags used to invoke the underlying binary. As is the case with all
+// libraries, binaries which contain Abseil code must ensure that separate
+// packages use the same compiled copy of Abseil to avoid a diamond dependency
+// problem, which can occur if two packages built with different Abseil
+// configuration settings are linked together. Diamond dependency problems in
+// C++ may manifest as violations to the One Definition Rule (ODR) (resulting in
+// linker errors), or undefined behavior (resulting in crashes).
+//
+// Diamond dependency problems can be avoided if all packages utilize the same
+// exact version of Abseil. Building from source code with the same compilation
+// parameters is the easiest way to avoid such dependency problems. However, for
+// package managers who cannot control such compilation parameters, we are
+// providing the file to allow you to inject ABI (Application Binary Interface)
+// stability across builds. Settings options in this file will neither change
+// API nor ABI, providing a stable copy of Abseil between packages.
+//
+// Care must be taken to keep options within these configurations isolated
+// from any other dynamic settings, such as command-line flags which could alter
+// these options. This file is provided specifically to help build and package
+// managers provide a stable copy of Abseil within their libraries and binaries;
+// other developers should not have need to alter the contents of this file.
+//
+// -----------------------------------------------------------------------------
+// Usage
+// -----------------------------------------------------------------------------
+//
+// For any particular package release, set the appropriate definitions within
+// this file to whatever value makes the most sense for your package(s). Note
+// that, by default, most of these options, at the moment, affect the
+// implementation of types; future options may affect other implementation
+// details.
+//
+// NOTE: the defaults within this file all assume that Abseil can select the
+// proper Abseil implementation at compile-time, which will not be sufficient
+// to guarantee ABI stability to package managers.
+//
+// -----------------------------------------------------------------------------
+// Type Compatibility Options
+// -----------------------------------------------------------------------------
+//
+// ABSL_OPTION_USE_STD_ANY
+//
+// This option controls whether absl::any is implemented as an alias to
+// std::any, or as an independent implementation.
+//
+// A value of 0 means to use Abseil's implementation.  This requires only C++11
+// support, and is expected to work on every toolchain we support.
+//
+// A value of 1 means to use an alias to std::any.  This requires that all code
+// using Abseil is built in C++17 mode or later.
+//
+// A value of 2 means to detect the C++ version being used to compile Abseil,
+// and use an alias only if a working std::any is available.  This option is
+// useful when you are building your entire program, including all of its
+// dependencies, from source.  It should not be used otherwise -- for example,
+// if you are distributing Abseil in a binary package manager -- since in
+// mode 2, absl::any will name a different type, with a different mangled name
+// and binary layout, depending on the compiler flags passed by the end user.
+// For more info, see https://abseil.io/about/design/dropin-types.
+//
+// User code should not inspect this macro.  To check in the preprocessor if
+// absl::any is a typedef of std::any, use the feature macro ABSL_USES_STD_ANY.
+
+#define ABSL_OPTION_USE_STD_ANY 2
+
+
+// ABSL_OPTION_USE_STD_OPTIONAL
+//
+// This option controls whether absl::optional is implemented as an alias to
+// std::optional, or as an independent implementation.
+//
+// A value of 0 means to use Abseil's implementation.  This requires only C++11
+// support, and is expected to work on every toolchain we support.
+//
+// A value of 1 means to use an alias to std::optional.  This requires that all
+// code using Abseil is built in C++17 mode or later.
+//
+// A value of 2 means to detect the C++ version being used to compile Abseil,
+// and use an alias only if a working std::optional is available.  This option
+// is useful when you are building your program from source.  It should not be
+// used otherwise -- for example, if you are distributing Abseil in a binary
+// package manager -- since in mode 2, absl::optional will name a different
+// type, with a different mangled name and binary layout, depending on the
+// compiler flags passed by the end user.  For more info, see
+// https://abseil.io/about/design/dropin-types.
+
+// A value of 2 means to detect the C++ version being used to compile Abseil,
+// and use an alias only if a working std::optional is available.  This option
+// should not be used when your program is not built from source -- for example,
+// if you are distributing Abseil in a binary package manager -- since in mode
+// 2, absl::optional will name a different template class, with a different
+// mangled name and binary layout, depending on the compiler flags passed by the
+// end user.
+//
+// User code should not inspect this macro.  To check in the preprocessor if
+// absl::optional is a typedef of std::optional, use the feature macro
+// ABSL_USES_STD_OPTIONAL.
+
+#define ABSL_OPTION_USE_STD_OPTIONAL 2
+
+
+// ABSL_OPTION_USE_STD_STRING_VIEW
+//
+// This option controls whether absl::string_view is implemented as an alias to
+// std::string_view, or as an independent implementation.
+//
+// A value of 0 means to use Abseil's implementation.  This requires only C++11
+// support, and is expected to work on every toolchain we support.
+//
+// A value of 1 means to use an alias to std::string_view.  This requires that
+// all code using Abseil is built in C++17 mode or later.
+//
+// A value of 2 means to detect the C++ version being used to compile Abseil,
+// and use an alias only if a working std::string_view is available.  This
+// option is useful when you are building your program from source.  It should
+// not be used otherwise -- for example, if you are distributing Abseil in a
+// binary package manager -- since in mode 2, absl::string_view will name a
+// different type, with a different mangled name and binary layout, depending on
+// the compiler flags passed by the end user.  For more info, see
+// https://abseil.io/about/design/dropin-types.
+//
+// User code should not inspect this macro.  To check in the preprocessor if
+// absl::string_view is a typedef of std::string_view, use the feature macro
+// ABSL_USES_STD_STRING_VIEW.
+
+#define ABSL_OPTION_USE_STD_STRING_VIEW 2
+
+
+// ABSL_OPTION_USE_STD_VARIANT
+//
+// This option controls whether absl::variant is implemented as an alias to
+// std::variant, or as an independent implementation.
+//
+// A value of 0 means to use Abseil's implementation.  This requires only C++11
+// support, and is expected to work on every toolchain we support.
+//
+// A value of 1 means to use an alias to std::variant.  This requires that all
+// code using Abseil is built in C++17 mode or later.
+//
+// A value of 2 means to detect the C++ version being used to compile Abseil,
+// and use an alias only if a working std::variant is available.  This option
+// is useful when you are building your program from source.  It should not be
+// used otherwise -- for example, if you are distributing Abseil in a binary
+// package manager -- since in mode 2, absl::variant will name a different
+// type, with a different mangled name and binary layout, depending on the
+// compiler flags passed by the end user.  For more info, see
+// https://abseil.io/about/design/dropin-types.
+//
+// User code should not inspect this macro.  To check in the preprocessor if
+// absl::variant is a typedef of std::variant, use the feature macro
+// ABSL_USES_STD_VARIANT.
+
+#define ABSL_OPTION_USE_STD_VARIANT 2
+
+#endif  // ABSL_BASE_OPTIONS_H_