• 0.63.1 (2026/01/06)

  • Fixed bug in release (doc) pipeline.

• 0.63.0 (2026/01/06)

  • Added batt::has_typed_arg<T>(args...)

• 0.62.0 (2025/12/08)

  • Fixed some Conan recipe regressions with the switch to Cor toolkit.
  • Added batt::BasicLatencyTimer (issue/27)
  • Made many bit manipulation functions constexpr (issue/25)
  • Fixed bugs in get_typed_arg<T&> (issue/28)
  • Added BATT_DECLARE_MAKE_STATUS_FN and BATT_REGISTER_CODES_AND_MAKE_STATUS_FN for easier creation of custom status code types and message tables.

• 0.61.1 (2025/10/06)

  • Fixed bug in batt::ObjectThreadStorage<T>/::ScopedSlot where different overloads of ScopedSlot::get(...) would create different thread-scoped objects.

• 0.61.0 (2025/10/06)

  • Added batt::ObjectThreadStorage<T>/::ScopedSlot for per-thread/per-object storage.
  • Fixed Conan editable mode.

• 0.60.1 (2025/08/08)

  • Added automatic calibration for batt::LatencyTimer to compensate for measurement overhead
  • Removed release client from .gitlab-ci.yml
  • Added batt::FlatDeque<T>; changed batt::Queue<T>
  • Increased memory available for handlers in batt::Task::await from 128 to 1024 bytes
  • batt::NotOkStatusWrapper now lazily constructs its std::ostringstream buffer

• 0.59.0 (2025/05/19)

  • Increased default kernel threads which can report BATT_DEBUG_INFO from 32 to 256
  • Removed -std=c++17 from ConanFile cpp_info.cxxflags
  • Added more packages with unusual Conan package name to CMake target name mappings:
    • abseil: absl
    • greg7mdp-gtl: gtl
    • robin-hood-hashing: robin_hood
  • Tuned MCSLock unit test for faster running times
  • Added batt::ThreadSpec (<batteries/cpu_align.hpp>) + text serialization/parser for human-writable specifications of CPU pinning schemes for thread pools (now used by batt::WorkerPool and batt::Runtime::DefaultScheduler)
    • Environment variable BATT_DEFAULT_SCHEDULER_IO_SPEC can also now be used to specify a mapping of executor objects to threads (which can be pinned to specific cores using BATT_DEFAULT_SCHEDULER_THREAD_SPEC)
  • Added test AsyncScalableGrantTest to provide a micro-benchmark comparison of batt::ScalableGrant and batt::SpinGrant, to make detecting regressions easier.
  • Added batt::FinalAct::run() (<batteries/finally.hpp>) to execute a finally block before block scope is exited
  • Moved batt::bit_count to new header <batteries/bit_ops.hpp>
  • Added batt::fixed_point::LinearProjection (<batteries/math.hpp>), which implements fast (no divisions), fixed-point integer scaling from an input range to an output domain
  • Added header <batteries/bit_ops.hpp> with support for popcount, rank/select, and various bit set operations, with hardware acceleration if available.
  • Moved BATT_UNWRAP macro from header <batteries/operators.hpp> to <batteries/utility.hpp>
  • Added batt::Optional<T>::value_or_panic(), which returns the value held by an Optional<T> or panics if the Optional is None
  • Added batt::IsOptional<T> meta-function/trait for compile-time detection of optional types
  • Added batt::RemoveOptional<T> meta-function/trait to remove a layer of Optional<T> wrapping (if possible)
  • Added batt::FastCountMetric<T>, a lower-overhead version of batt::CountMetric<T> that uses thread-local data to avoid atomic operations on the metric update path.
  • Improvements to batt::seq::LoopControl
  • Added <batteries/typed_args.hpp>

• 0.58.5 (2025/01/30)

  • Disabled code coverage in pipelines (will re-enable when performance regression(s) are investigated/fixed)
  • Fixed compatibility issue by relaxing CMake version requirement to 3.22

• 0.58.2 (2025/01/13)

  • Fix some doc comment typos
  • Expand the coding style document
  • Add BATT_SUPPRESS_IF_GCC_VERSION(version, warning_id_str) to <batteries/suppress.hpp>
  • Fix some spurious warnings to enable gcc 13 support (not yet added to pipelines)

• 0.58.1 (2024/11/18)

  • Add code coverage tools to the pipeline docker image
  • Bug fixes/improvements to scripts
  • Fix Conan editable mode
  • Fix bugs re: multiple check failures suppress full trace when multi-threaded
  • Fix bug in Optional that allows implicit conversion from primitive type to strong typedef

• 0.58.0 (2024/10/10)

  • Added support for throwing out of Batteries-based code into a larger app context that uses exceptions.
    • batt::StatusException - exception type that wraps a batt::Status plus an optional extra message string; derives from std::runtime_error
    • BATT_THROW_IF_NOT_OK(expr) - macro that accepts any expression evaluating to a batt::Status or batt::StatusOr<T>; expands to statement that checks for ok and throws batt::StatusException if not ok; supports stream-insertion (<<) of extra information similar to BATT_CHECK
    • BATT_OK_RESULT_OR_THROW(expr) - macro that accepts an expression that evalutes to a batt::StatusOr<T> and expands to an expression that checks for ok (throws batt::StatusException if not), plus a dereference of the StatusOr if it is ok

• 0.57.2 (2024/10/02)

  • Fixed compilation error on gcc with C++ std versions before 20 (17, gnu17).

• 0.57.1 (2024/10/01)

  • Fixed #23 (bug) - batt::seq::chain() produces sequence that gives incorrect result for peek() when first sequence empty, second sequence non-empty.
  • Upgrade script submodule - moved test from top-level Makefile to script/conan-targets.mk; added script/run-tests.sh.

• 0.57.0 (2024/09/25)

  • Added SSL/TLS (https://) support to batt::HttpClient
    • SSL context initialization can be customized by supplying a std::function to batt::HttpClient::set_ssl_init_fn. The function should have the signature void(Optional<boost::asio::ssl::context>&, const HostAddress&), and should construct the passed optional context in-place (using batt::Optional::emplace).
  • Worked around race conditions in conan install when downloading/building new packages
  • Added support in CI pipelines for uploading any packages that were built from source during make install to a cache artifact server.
  • Upgraded dependencies in the lockfile (and also added openssl, for https support).

• 0.56.2 (2024/09/10)

  • Fixed race condition bugs in batt::ReadWriteLock that could lead to panics or deadlocks
  • Added HoldOwnership and ReleaseOwnership modes for all WatchAtomic<T> simple modification functions
    • HoldOwnership is the default; it is slightly faster and more scalable, but assumes that the caller will keep the Watch object alive until the function returns
    • ReleaseOwnership is slightly slower and less scalable, but is safe to call even when the modification being performed to the Watch value will cause the Watch itself to be deleted
  • Added a batt::FakeTimeService instance to batt::FakeExecutionContext; added support in batt::FakeExecutionContext::run_with_random_seed for simulated timer expirations

• 0.56.0 (2024/09/06)

  • Renamed batt::Grant to batt::SpinGrant
  • Introduced new Grant implementation, batt::ScalableGrant
    • Uses explicit mutex locks and a waiter queue to scale more gracefully than the old Grant (now SpinGrant), where all contenders to claim Grant count use a single batt::Watch and CAS-like loops
    • AsyncScalableGrantTest.ScalabilityBenchmark test (newly added) demonstrates that, as expected, SpinGrant degrades linearly with the number of contenders, whereas ScalableGrant maintains a constant throughput even when faced with hundreds or thousands of Tasks competing for Grant count.
  • batt::Grant is now a type alias to batt::ScalableGrant
  • Minor bug fixes that cause spurious failed checks when panicking on another thread

• 0.55.1 (2024/07/25)

  • Fixed bug where printing a batt::WaitForResource to a std::ostream results in a crash
  • Added test for std::ostream printing of batt::CountMetric

• 0.55.0 (2024/07/19)

  • Added batt::LazyLatch<T> - like batt::Latch<T> but automatically initializes when value is requested, via an init_fn passed in at construction time.

• 0.54.0

  • Added template parameter bool kAllowAlloc for batt::SmallFn, which enables falling back to dynamic (heap) allocation if a type-erased function is too large to fit in the inline small object buffer (similar to batt::SmallVec).
  • Added batt::InstanceCounter<T> for easy debug tracking of the number of active instances for a given type.

• 0.53.0

  • Batteries now uses Conan version ranges for dependencies + lock files.
  • Added batt::StaticTypeMap<KeyTupleT, ValueT>, to store a fixed-size collection of values indexed by distinct types.

• 0.52.5

  • Added batt::ReadWriteMutex<T> to wrap batt::ReadWriteLock and an instance of T, using an API similar to batt::Mutex<T>.

• 0.52.3

  • Fixed race condition bug in WatchAtomic::poke()/Queue<T>::poke() that could cause the next waiter to miss the poke.

• 0.52.1

  • Added a static assert to detect incorrect use of batt::seq::map (when the map function returns void).

• 0.52.0

  • Added batt::HttpServer: a basic HTTP/1.1 server implementation based on batt::Task, sharing common code with batt::HttpClient
  • Added cleanup_fn optional argument to batt::Queue<T>::drain
  • Added batt::HttpMessageBase::close() (inherited by batt::HttpRequest and batt::HttpResponse)
  • Added batt::HttpMessageBase::invoke_stream_writer(writer_fn) (inherited by batt::HttpRequest and batt::HttpResponse)
  • Moved serialize method from batt::HttpRequest to batt::HttpMessageBase so it can be used by batt::HttpResponse
  • Moved RequestInfo to top level batt::HttpMessageInfo so it can be used with requests and responses

• 0.51.1

  • Added BATT_ASSERT statements to detect attempts to access the contents of an invalid batt::Optional<T>.

• 0.51.0

  • Added batt::bit_count, a portable version of the "how many 1-bits in this integer" machine instruction (POPCOUNT on Intel).

• 0.50.9

  • Added better explanation of the batt::Mutex<T>::with_lock (doc comments).
  • Added a \return doc tag for WatchAtomic<T>::set_value.

• 0.50.7

  • Added patchelf package to Docker image for CI/CD pipelines.
  • Added batt::InlineSubTask<kStackBufferSize> (#include <batteries/async/inline_sub_task.hpp>) for easy allocation/launching of sub-tasks using part of the stack memory of an existing task.

• 0.50.6

  • Added environment variable BATT_DEFAULT_SCHEDULER_PIN_CPU to control whether batt::Runtime::default_scheduler() pins its thread pool 1:1 to specific CPUs.

• 0.50.5

  • Added batt::ReadWriteLock, an implementation of a fair reader/writer mutex as described in "Synchronization Without Contention" (Mellor-Crummey, Scott, 1991)
  • Changed the Dockerfile to install all Python packages (including Conan) in a virtual environment (/opt/venv) instead of the ambient environment.
  • Upgrade the Dockerfile to install Conan version 2.0.16.
  • Added batt::WatchAtomic<T>::poll(), which yields the current task and then reloads/returns the watch value.

• 0.50.3

  • Fixed a problem with the CMakeLists.txt and conanfile.py that caused unit tests to be (re-)built when running conan install from a downstream project.

• 0.50.1

  • Added batt::AtomicCounterGauge<T>, an atomic variable with both gauge-like (moves up and down) and counter-like (add/subtract counters are monotonically increasing) semantics.

• 0.49.2

  • Added batt::BoolStatus (<batteries/bool_status.hpp>), an enum that has true/false/unknown values and overloaded logical operators.

• 0.49.1

  • Added to <batteries/type_traits.hpp>:
    • is_any_true(expr0, expr1, expr2, ...): (constexpr) Returns true (and short circuits) at the first true-valued argument; else false
    • are_all_true(expr0, expr1, expr2, ...): (constexpr) Returns false (and short circuits) at the first false-valued argument else true
    • IsOneOf<T, M0, M1, ...>: (inline constexpr bool) True iff T is exactly one of the set M0, M1, ...
    • DecaysToOneOf<T, M0, M1, ...>: (inline constexpr bool) True iff std::decay_t<T> is one of the set M0, M1, ...

• 0.49.0

  • Added BATT_RETURN_OK_RESULT(expr), which unwraps and returns expr if it evaluates to an ok status, continues without returning otherwise.

• 0.48.9/0.48.10 (2023/11/27)

  • Fix conan install bug in conanfile.py: search for script/batt.py relative to the source folder, in addition to the conanfile.py folder.

• 0.48.8 (2023/11/21)

  • Add batt::Promise<T>::is_ready() to test whether a future value or error has been set.

• 0.48.4 (2023/11/16)

  • batt::Status now preserves message strings from std::error_code (for the built-in error categories: std::system_category(), std::generic_category(), std::future_category(), and std::iostream_category()).

• 0.48.3 (2023/11/15)

  • Added header operators.hpp:
    • BATT_OBJECT_PRINT_IMPL(inline_decl, type, fields_tuple)
      • Defines << to print the object to an ostream
    • BATT_OBJECT_EQUALS_IMPL(inline_decl, type, fields_tuple)
      • Defines == as conjunction of field-wise equality
    • BATT_OBJECT_LESS_THAN_IMPL(inline_decl, type, fields_tuple)
      • Defines < as a lexicographical ordering of the field orders
    • BATT_EQUALITY_COMPARABLE(inline_decl, left_type, right_type)
      • Defines != based on ==
    • BATT_TOTALLY_ORDERED(inline_decl, left_type_right_type)
      • Defines >, <=, and >= based on <

• 0.48.2 (2023/11/06)

  • Added batt::Future<T>::from_value, batt::Future<T>::from_error: convenient API for making completed Futures.
  • Print batt::Status as GROUP.CODE:MESSAGE instead of VALUE:MESSAGE; this allows the savvy reader to convert printed Status values to, for example, errno codes by inspection.

• 0.47.0 (2023/10/17)

  • Added batt::Future<T>::and_then for monadic future composition.

• 0.33.0 (2023/05/19)

  • Added Conan options for build variants that affect ABI:
    • header_only
    • glog_support
    • protobuf_support
    • asserts_enabled
    • shared
  • Added <batteries/stacktrace.hpp>, which includes boost stacktrace and suppresses spurious GCC warnings in the boost code.
  • Added a runtime check system to <batteries/config.hpp> that computes a "feature [bit-]mask" which captures the build variant; this is done for each compilation unit that includes config.hpp (using static init of a bool in an anonymous namespace) and compared to a global, canonical feature mask. In this way, we can now detect bugs where different libraries were built with different Batteries feature settings and halt the program before undefined behavior ensues.
  • Added new macros to control optimization suppression in the code:
    • BATT_GCC_BEGIN_OPTIMIZE(setting) - setting must be a string literal, e.g. "O0"
    • BATT_GCC_END_OPTIMIZE() - reverts the optimization level set by BATT_GCC_BEGIN_OPTIMIZE
    • BATT_BEGIN_NO_OPTIMIZE() - begins a section in which optimization is completely disabled
    • BATT_END_NO_OPTIMIZE() - ends a section begun by BATT_BEGIN_NO_OPTIMIZE
  • Enabling BATT_ASSERT statements can now be done independent of the NDEBUG define, using BATT_ASSERTS_ENABLED, which is controlled by the Conan config via the asserts_enabled option, which can be None (default), True, or False. If BATT_ASSERTS_ENABLED is not defined (i.e., asserts_enabled is None), then asserts are only enabled when NDEBUG is defined, like before.
  • Added support for std::ostream operator<< to batt::LogLevel (<batteries/status.hpp>)
  • Fixed silent ABI breakage bug in batt::detail::NotOkStatusWrapper that causes aborts at runtime when some libraries are compiled with BATT_GLOG_AVAILABLE and some without.
  • Fixed an overly aggressive check in batt::Task

• 0.31.3 (2023/05/03)

  • Fixed bug in TakeNSource that causes hang after limit is reached (instead of returning batt::StatusCode::kEndOfStream).

• 0.31.0 (2023/05/03)

  • Added batt::SingleBufferSource.

• 0.30.0 (2023/04/13)

  • Fix #4 (Added std::ostream& operator<<(std::ostream&, batt::Watch<T>))
  • Fix #5 (Deadlock if a failed BATT_CHECK generates another failed check when trying to print the message)
  • Fix #6 (Added batt::Watch<T>::reset())

• 0.29.0 (2023/03/31)

  • Add batt::seq::zip.

• 0.28.5 (2023/03/17)

  • Add doc comment for batt::getenv_as.

• 0.28.4 (2023/03/17)

  • Added batt::Optional::or_else(Fn) to match std::optional.
  • Changed batt::require_fail_thread_default_log_level() to return batt::Optional<batt::LogLevel>& instead of batt::LogLevel&, and made it default to the current global setting when it is batt::None.

• 0.28.3 (2023/03/13)

  • Fix bug that prevented the use of batt::Future<T>::await.

• 0.27.1 (2023/03/08)

  • Fixed typo in case_of.hpp doc.
  • Added support for silent conversion of batt::StatusOr<batt::NoneType> to batt::Status.

• 0.27.0 (2023/03/07)

  • Added BATT_CHECK_TYPE(type, expr) to <batteries/static_assert.hpp>:
    • At runtime, evaluates to just expr, but adds a compile-time assertion that the type of expr is type.

• 0.26.0 (2023/03/04)

  • Added batt::Task::DeferStart{bool} option to suppress automatic Task starting; also:
    • Added member fn batt::Task::is_started()
    • Added member fn batt::Task::start()
    • Added class batt::Task::Options

• 0.25.3 (2023/03/02)

  • Fixed many missing functions/operators for batt::Optional<T&> partial specialization.

• 0.25.0 (2023/02/23)

  • Added batt::Task::await_signal (moved from "upper layers").

• 0.24.6 (2023/02/22)

  • Added support for MacOS/Clang build pipelines
  • Added batt::Task::spawn()
  • Added batt::NoDestruct<T>

• 0.23.1 (2023/02/06)

  • Fixed bug in script/run-with-docker.sh
  • Added xxd to docker images

• 0.22.1 (2023/01/27)

  • Added batt::DefaultInitialized, a type that implicitly converts to any default-constructible type.
  • Added a step parameter (type batt::TransferStep &, batteries/async/fetch.hpp) that allows callers to determine which step failed when batt::transfer_chunked_data returns an error.

• 0.21.0 (2023/01/25)

  • Added batt::register_error_category to allow applications to specify how error_code values with custom error_category objects should be converted to batt::Status.
  • Upgraded boost to 1.81.0
  • Upgraded gtest to 1.13.0

• 0.20.1 (2023/01/18)

  • Added batt::transfer_chunked_data (in batteries/async/fetch.hpp).

• 0.19.8 (2023/01/11)

  • Upgrade to Conan 1.56 (from 1.53).

• 0.19.6 (2022/12/19)

  • Fixed build error with batt::to_status(std::error_code)

• 0.19.5 (2022/12/16)

  • Fixed crash bug caused by accidental implicit conversion from error_code enum values to batt::Status.

• 0.19.2 (2022/12/16)

  • Fixed test regression by updating the expected error status to match the boost::system::error_code value.

• 0.19.1 (2022/12/16)

  • Added accurate translation of more boost::system::error_code values into batt::Status.

• 0.19.0 (2022/12/14)

  • Added batt::Latch<T>::set_error to explicitly set the Latch to an error status for better readability.
  • Added new header batteries/async/fetch.hpp with:
    • batt::fetch_chunk: blocking API for no-copy input streams with an async_fetch method
    • batt::BasicScopedChunk<Stream>: automatically calls consume on fetched data at scope exit

• 0.18.1 (2022/12/09)

  • Added batt::PinnablePtr<T>.

• 0.18.0 (2022/12/07)

  • Added batt::Channel<T>::async_read, along with unit tests for the async methods of batt::Channel<T>.

• 0.17.1 (2022/12/02)

  • Added batt::Runtime::reset() and batt::Runtime::is_halted() so that downstream libraries that use a Google Test global environment to start/stop batt::Runtime can restart the default thread pool, for GTEST_REPEAT/--gtest_repeat testing.

• 0.16.2 (2022/11/30)

  • Fixed a broken link in the release notes.

• 0.16.1 (2022/11/30)

  • Added release notes (this document) to the doc pages.

• 0.16.0 (2022/11/30)

  • Added clamp min/max functions to batt::Watch, to atomically enforce upper/lower bounds on the watched value.