diff options
Diffstat (limited to 'absl')
| -rw-r--r-- | absl/FAQ.md | 144 | ||||
| -rwxr-xr-x | absl/abseil.podspec.gen.py | 18 | ||||
| -rw-r--r-- | absl/base/config.h | 14 | ||||
| -rw-r--r-- | absl/container/node_hash_set.h | 4 | ||||
| -rw-r--r-- | absl/debugging/failure_signal_handler.cc | 13 | ||||
| -rw-r--r-- | absl/flags/BUILD.bazel | 1 | ||||
| -rw-r--r-- | absl/flags/CMakeLists.txt | 1 | ||||
| -rw-r--r-- | absl/flags/internal/flag.cc | 29 | ||||
| -rw-r--r-- | absl/flags/internal/flag.h | 19 |
9 files changed, 43 insertions, 200 deletions
diff --git a/absl/FAQ.md b/absl/FAQ.md deleted file mode 100644 index af72130..0000000 --- a/absl/FAQ.md +++ /dev/null @@ -1,144 +0,0 @@ -# Abseil FAQ - -## Is Abseil the right home for my utility library? - -Most often the answer to the question is "no." As both the [About -Abseil](https://abseil.io/about/) page and our [contributing -guidelines](https://github.com/abseil/abseil-cpp/blob/master/CONTRIBUTING.md#contribution-guidelines) -explain, Abseil contains a variety of core C++ library code that is widely used -at [Google](https://www.google.com/). As such, Abseil's primary purpose is to be -used as a dependency by Google's open source C++ projects. While we do hope that -Abseil is also useful to the C++ community at large, this added constraint also -means that we are unlikely to accept a contribution of utility code that isn't -already widely used by Google. - -## How to I set the C++ dialect used to build Abseil? - -The short answer is that whatever mechanism you choose, you need to make sure -that you set this option consistently at the global level for your entire -project. If, for example, you want to set the C++ dialect to C++17, with -[Bazel](https://bazel/build/) as the build system and `gcc` or `clang` as the -compiler, there several ways to do this: -* Pass `--cxxopt=-std=c++17` on the command line (for example, `bazel build - --cxxopt=-std=c++17 ...`) -* Set the environment variable `BAZEL_CXXOPTS` (for example, - `BAZEL_CXXOPTS=-std=c++17`) -* Add `build --cxxopt=-std=c++17` to your [`.bazelrc` - file](https://docs.bazel.build/versions/master/guide.html#bazelrc) - -If you are using CMake as the build system, you'll need to add a line like -`set(CMAKE_CXX_STANDARD 17)` to your top level `CMakeLists.txt` file. See the -[CMake build -instructions](https://github.com/abseil/abseil-cpp/blob/master/CMake/README.md) -for more information. - -For a longer answer to this question and to understand why some other approaches -don't work, see the answer to "What is ABI and why don't you recommend using a -pre-compiled version of Abseil?" - -## What is ABI and why don't you recommend using a pre-compiled version of Abseil? - -For the purposes of this discussion, you can think of -[ABI](https://en.wikipedia.org/wiki/Application_binary_interface) as the -compiled representation of the interfaces in code. This is in contrast to -[API](https://en.wikipedia.org/wiki/Application_programming_interface), which -you can think of as the interfaces as defined by the code itself. [Abseil has a -strong promise of API compatibility, but does not make any promise of ABI -compatibility](https://abseil.io/about/compatibility). Let's take a look at what -this means in practice. - -You might be tempted to do something like this in a -[Bazel](https://bazel.build/) `BUILD` file: - -``` -# DON'T DO THIS!!! -cc_library( - name = "my_library", - srcs = ["my_library.cc"], - copts = ["-std=c++17"], # May create a mixed-mode compile! - deps = ["@com_google_absl//absl/strings"], -) -``` - -Applying `-std=c++17` to an individual target in your `BUILD` file is going to -compile that specific target in C++17 mode, but it isn't going to ensure the -Abseil library is built in C++17 mode, since the Abseil library itself is a -different build target. If your code includes an Abseil header, then your -program may contain conflicting definitions of the same -class/function/variable/enum, etc. As a rule, all compile options that affect -the ABI of a program need to be applied to the entire build on a global basis. - -C++ has something called the [One Definition -Rule](https://en.wikipedia.org/wiki/One_Definition_Rule) (ODR). C++ doesn't -allow multiple definitions of the same class/function/variable/enum, etc. ODR -violations sometimes result in linker errors, but linkers do not always catch -violations. Uncaught ODR violations can result in strange runtime behaviors or -crashes that can be hard to debug. - -If you build the Abseil library and your code using different compile options -that affect ABI, there is a good chance you will run afoul of the One Definition -Rule. Examples of GCC compile options that affect ABI include (but aren't -limited to) language dialect (e.g. `-std=`), optimization level (e.g. `-O2`), -code generation flags (e.g. `-fexceptions`), and preprocessor defines -(e.g. `-DNDEBUG`). - -If you use a pre-compiled version of Abseil, (for example, from your Linux -distribution package manager or from something like -[vcpkg](https://github.com/microsoft/vcpkg)) you have to be very careful to -ensure ABI compatibility across the components of your program. The only way you -can be sure your program is going to be correct regarding ABI is to ensure -you've used the exact same compile options as were used to build the -pre-compiled library. This does not mean that Abseil cannot work as part of a -Linux distribution since a knowledgeable binary packager will have ensured that -all packages have been built with consistent compile options. This is one of the -reasons we warn against - though do not outright reject - using Abseil as a -pre-compiled library. - -Another possible way that you might afoul of ABI issues is if you accidentally -include two versions of Abseil in your program. Multiple versions of Abseil can -end up within the same binary if your program uses the Abseil library and -another library also transitively depends on Abseil (resulting in what is -sometimes called the diamond dependency problem). In cases such as this you must -structure your build so that all libraries use the same version of Abseil. -[Abseil's strong promise of API compatibility between -releases](https://abseil.io/about/compatibility) means the latest "HEAD" release -of Abseil is almost certainly the right choice if you are doing as we recommend -and building all of your code from source. - -For these reasons we recommend you avoid pre-compiled code and build the Abseil -library yourself in a consistent manner with the rest of your code. - -## What is "live at head" and how do I do it? - -From Abseil's point-of-view, "live at head" means that every Abseil source -release (which happens on an almost daily basis) is either API compatible with -the previous release, or comes with an automated tool that you can run over code -to make it compatible. In practice, the need to use an automated tool is -extremely rare. This means that upgrading from one source release to another -should be a routine practice that can and should be performed often. - -We recommend you update to the latest release of Abseil as often as -possible. Not only will you pick up bug fixes more quickly, but if you have good -automated testing, you will catch and be able to fix any [Hyrum's -Law](https://www.hyrumslaw.com/) dependency problems on an incremental basis -instead of being overwhelmed by them and having difficulty isolating them if you -wait longer between updates. - -If you are using the [Bazel](https://bazel.build/) build system and its -[external dependencies](https://docs.bazel.build/versions/master/external.html) -feature, updating the -[`http_archive`](https://docs.bazel.build/versions/master/repo/http.html#http_archive) -rule in your -[`WORKSPACE`](https://docs.bazel.build/versions/master/be/workspace.html) for -`com_google_abseil` to point to the latest release is all you need to do. You -can commit the updated `WORKSPACE` file to your source control every time you -update, and if you have good automated testing, you might even consider -automating this. - -One thing we don't recommend is using GitHub's `master.zip` files (for example -[https://github.com/abseil/abseil-cpp/archive/master.zip](https://github.com/abseil/abseil-cpp/archive/master.zip)), -which are always the latest commit in the `master` branch, to implement live at -head. Since these `master.zip` URLs are not versioned, you will lose build -reproducibility. In addition, some build systems, including Bazel, will simply -cache this file, which means you won't actually be updating to the latest -release until your cache is cleared or invalidated. diff --git a/absl/abseil.podspec.gen.py b/absl/abseil.podspec.gen.py index 2bf153c..6aefb79 100755 --- a/absl/abseil.podspec.gen.py +++ b/absl/abseil.podspec.gen.py @@ -46,18 +46,6 @@ Pod::Spec.new do |s| s.watchos.deployment_target = '2.0' """ -# Limited platforms that abseil supports. -# This is mainly because of sigaltstack unavailable on watchOS. -LIMITED_SUPPORT_PLATFORMS = [ - "ios.deployment_target = '7.0'", - "osx.deployment_target = '10.9'", -] - -# Custom specification per rule. -CUSTOM_SPEC_MAP = { - "//absl/debugging:failure_signal_handler": LIMITED_SUPPORT_PLATFORMS, -} - # Rule object representing the rule of Bazel BUILD. Rule = collections.namedtuple( "Rule", "type name package srcs hdrs textual_hdrs deps visibility testonly") @@ -200,12 +188,6 @@ def write_podspec_rule(f, rule, depth): name = get_spec_name(dep.replace(":", "/")) f.write("{indent}{var}.dependency '{dep}'\n".format( indent=indent, var=spec_var, dep=name)) - # Writes custom specification. - custom_spec = CUSTOM_SPEC_MAP.get(rule.package + ":" + rule.name) - if custom_spec: - for spec in custom_spec: - f.write("{indent}{var}.{spec}\n".format( - indent=indent, var=spec_var, spec=spec)) def write_indented_list(f, leading, values): diff --git a/absl/base/config.h b/absl/base/config.h index eac5d26..ee99f94 100644 --- a/absl/base/config.h +++ b/absl/base/config.h @@ -316,13 +316,19 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' || #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 __clang_major__ > 3 || (__clang_major__ == 3 && __clang_minor__ >= 6) +// Clang >= 3.6 +#if __has_feature(cxx_exceptions) +#define ABSL_HAVE_EXCEPTIONS 1 +#endif // __has_feature(cxx_exceptions) +#else +// Clang < 3.6 +// 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) +#endif // __clang_major__ > 3 || (__clang_major__ == 3 && __clang_minor__ >= 6) // Handle remaining special cases and default to exceptions being supported. #elif !(defined(__GNUC__) && (__GNUC__ < 5) && !defined(__EXCEPTIONS)) && \ diff --git a/absl/container/node_hash_set.h b/absl/container/node_hash_set.h index 0e2dee5..ad54b6d 100644 --- a/absl/container/node_hash_set.h +++ b/absl/container/node_hash_set.h @@ -77,7 +77,7 @@ struct NodeHashSetPolicy; // // // Create a node hash set of three strings // absl::node_hash_map<std::string, std::string> ducks = -// {"huey", "dewey"}, "louie"}; +// {"huey", "dewey", "louie"}; // // // Insert a new element into the node hash map // ducks.insert("donald"}; @@ -111,7 +111,7 @@ class node_hash_set // * Initializer List constructor // // absl::node_hash_set<std::string> set2 = - // {{"huey"}, {"dewey"}, {"louie"},}; + // {{"huey"}, {"dewey"}, {"louie"}}; // // * Copy constructor // diff --git a/absl/debugging/failure_signal_handler.cc b/absl/debugging/failure_signal_handler.cc index 470d676..cd141ec 100644 --- a/absl/debugging/failure_signal_handler.cc +++ b/absl/debugging/failure_signal_handler.cc @@ -24,6 +24,10 @@ #include <unistd.h> #endif +#ifdef __APPLE__ +#include <TargetConditionals.h> +#endif + #ifdef ABSL_HAVE_MMAP #include <sys/mman.h> #endif @@ -44,6 +48,11 @@ #ifndef _WIN32 #define ABSL_HAVE_SIGACTION +// Apple WatchOS and TVOS don't allow sigaltstack +#if !(defined(TARGET_OS_WATCH) && TARGET_OS_WATCH) && \ + !(defined(TARGET_OS_TV) && TARGET_OS_TV) +#define ABSL_HAVE_SIGALTSTACK +#endif #endif namespace absl { @@ -117,7 +126,7 @@ const char* FailureSignalToString(int signo) { } // namespace debugging_internal -#ifndef _WIN32 +#ifdef ABSL_HAVE_SIGALTSTACK static bool SetupAlternateStackOnce() { #if defined(__wasm__) || defined (__asjms__) @@ -169,7 +178,7 @@ static bool SetupAlternateStackOnce() { // Returns the appropriate flag for sig_action.sa_flags // if the system supports using an alternate stack. static int MaybeSetupAlternateStack() { -#ifndef _WIN32 +#ifdef ABSL_HAVE_SIGALTSTACK ABSL_ATTRIBUTE_UNUSED static const bool kOnce = SetupAlternateStackOnce(); return SA_ONSTACK; #else diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel index d2ca5c6..cdb4e7e 100644 --- a/absl/flags/BUILD.bazel +++ b/absl/flags/BUILD.bazel @@ -41,6 +41,7 @@ cc_library( ":config", ":handle", ":registry", + "//absl/base", "//absl/base:config", "//absl/base:core_headers", "//absl/memory", diff --git a/absl/flags/CMakeLists.txt b/absl/flags/CMakeLists.txt index 20e6682..1d25f0d 100644 --- a/absl/flags/CMakeLists.txt +++ b/absl/flags/CMakeLists.txt @@ -27,6 +27,7 @@ absl_cc_library( LINKOPTS ${ABSL_DEFAULT_LINKOPTS} DEPS + absl::base absl::config absl::flags_config absl::flags_handle diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc index ba70da9..721e411 100644 --- a/absl/flags/internal/flag.cc +++ b/absl/flags/internal/flag.cc @@ -80,41 +80,22 @@ class MutexRelock { absl::Mutex* mu_; }; -// This global lock guards the initialization and destruction of data_guard_, -// which is used to guard the other Flag data. -ABSL_CONST_INIT static absl::Mutex flag_mutex_lifetime_guard(absl::kConstInit); - } // namespace void FlagImpl::Init() { - { - absl::MutexLock lock(&flag_mutex_lifetime_guard); - - // Must initialize data guard for this flag. - if (!is_data_guard_inited_) { - new (&data_guard_) absl::Mutex; - is_data_guard_inited_ = true; - } - } + new (&data_guard_) absl::Mutex; absl::MutexLock lock(reinterpret_cast<absl::Mutex*>(&data_guard_)); - if (value_.dynamic != nullptr) { - inited_.store(true, std::memory_order_release); - } else { - // Need to initialize cur field. - value_.dynamic = MakeInitValue().release(); - StoreAtomic(); - inited_.store(true, std::memory_order_release); - } + value_.dynamic = MakeInitValue().release(); + StoreAtomic(); } // Ensures that the lazily initialized data is initialized, // and returns pointer to the mutex guarding flags data. absl::Mutex* FlagImpl::DataGuard() const { - if (ABSL_PREDICT_FALSE(!inited_.load(std::memory_order_acquire))) { - const_cast<FlagImpl*>(this)->Init(); - } + absl::call_once(const_cast<FlagImpl*>(this)->init_control_, &FlagImpl::Init, + const_cast<FlagImpl*>(this)); // data_guard_ is initialized. return reinterpret_cast<absl::Mutex*>(&data_guard_); diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h index ef30a22..b426ccb 100644 --- a/absl/flags/internal/flag.h +++ b/absl/flags/internal/flag.h @@ -24,6 +24,7 @@ #include <string> #include <type_traits> +#include "absl/base/call_once.h" #include "absl/base/config.h" #include "absl/base/thread_annotations.h" #include "absl/flags/config.h" @@ -281,10 +282,8 @@ class FlagImpl { help_(help.source), help_source_kind_(static_cast<uint8_t>(help.kind)), def_kind_(static_cast<uint8_t>(FlagDefaultKind::kGenFunc)), - is_data_guard_inited_(false), modified_(false), on_command_line_(false), - inited_(false), counter_(0), callback_(nullptr), default_src_(default_value_gen), @@ -406,20 +405,28 @@ class FlagImpl { // Indicates if help message was supplied as literal or generator func. const uint8_t help_source_kind_ : 1; + // ------------------------------------------------------------------------ + // The bytes containing the const bitfields must not be shared with bytes + // containing the mutable bitfields. + // ------------------------------------------------------------------------ + + // Unique tag for absl::call_once call to initialize this flag. + // + // The placement of this variable between the immutable and mutable bitfields + // is important as prevents them from occupying the same byte. If you remove + // this variable, make sure to maintain this property. + absl::once_flag init_control_; + // Mutable flag's state (guarded by `data_guard_`). // If def_kind_ == kDynamicValue, default_src_ holds a dynamically allocated // value. uint8_t def_kind_ : 1 ABSL_GUARDED_BY(*DataGuard()); - // Protects against multiple concurrent constructions of `data_guard_`. - bool is_data_guard_inited_ : 1; // Has this flag's value been modified? bool modified_ : 1 ABSL_GUARDED_BY(*DataGuard()); // Has this flag been specified on command line. bool on_command_line_ : 1 ABSL_GUARDED_BY(*DataGuard()); - // Indicates that the flag state is initialized. - std::atomic<bool> inited_; // Mutation counter int64_t counter_ ABSL_GUARDED_BY(*DataGuard()); // Optional flag's callback and absl::Mutex to guard the invocations. |