v3.7.0

Major release with improved broker startup controls, C shared library support for querying broker and core status, and updates to build requirements and third party libraries.

Fixed

• Fixed several timing and iteration coordination issues, including sequence counter resets, mixed value and message federate iterations, and disconnect handling with the wait_for_current_time flag.
• Fixed an incorrect timer index that could lead to sporadic test failures.
• Fixed the C shared library declarations for global input registration functions to return HelicsInput.
• Fixed helicsGetDataType to recognize the raw, map, and custom type aliases.
• Fixed Cygwin build configuration issues.

Changed

• C++20 is now the minimum required C++ standard.
• Updated the minimum Boost build requirement to 1.83.
• Updated the handling of HELICS_TIME_MAXTIME, HELICS_TIME_BIGTIME, and simulation termination times.
• Updated third party libraries, including Asio, CLI11, fmt, spdlog, toml, units, ZeroMQ, and GoogleTest.
• Updated build and CI support, including builds with CMake 4.2, Boost 1.92, and C++26.

Added

• Added --local_federates, --local_subbrokers, and --required_federates broker options to control when a federation may enter initialization mode.
• Added C shared library functions to check whether a broker is a root broker or whether a broker or core can accept new federates.
• Added HELICS_PROPERTY_INT_VALUE_BUFFER_WARNING and the --value_buffer_warning federate option to report when queued value buffers exceed a configurable threshold.
• Added distinct maximum-time and termination-time constants to the C shared library API.
• Added [[nodiscard]] annotations to C++98 interface methods where their return values should be used.