The rapids-logger project defines an easy way to produce a project-specific logger using the excellent spdlog package.
This project has two primary goals:
- Ensure that projects wishing to provide their own logger may do so easily without needing to reimplement their own custom wrappers around spdlog.
- Ensure that custom logger implementations based on spdlog do not leak any spdlog (or fmt) symbols, allowing the safe coexistence of different projects in the same environment even if they use different versions of spdlog.
rapids-logger is designed to be used via CMake.
Its CMakeLists.txt defines a function rapids_make_logger that can be used to produce a project-specific logger class in a provided namespace.
The resulting logger exposes spdlog-like functionality via the PImpl idiom to avoid exposing spdlog symbols publicly.
It uses CMake and template C++ files to generate a public header file to describe the user interface and an inline header that should be placed in a single TU by consumers to compile the implementation.
To simplify usage, each invocation of the function produces two CMake targets, one representing the public header and one representing a trivial source file including the inline header.
Projects using rapids-logger should make the first target part of their public link interface while the latter should be linked to privately so that it is compiled into the project's library without public exposure.
Logging levels are controlled both at compile-time and at runtime.
To mirror spdlog, each generated logger ships with a set of logging macros <project-name>_LOG_<log-level>.
These macros are compiled based on the value of the compile-time variable <project-name>_LOG_ACTIVE_LEVEL.
For example, a project called "RAPIDS" will be able to write code like this:
RAPIDS_LOG_DEBUG("Some message to be shown when the debug level is enabled");
and control whether that message is shown by compiling the code with RAPIDS_LOG_ACTIVE_LEVEL=RAPIDS_LOG_LEVEL_DEBUG.
Additionally, the default runtime logging level can be controlled at compile time through the LOGGER_DEFAULT_LEVEL argument of rapids_make_logger.
This default runtime value allows for compiling with INFO level messages available, but only showing WARN or higher at runtime by default.
Users can then opt in to more verbose logging at runtime using default_logger().set_level(...).
Each project is endowed with its own definition of levels, so different projects in the same environment may be safely configured independently of each other and of spdlog.
Each project is also given a default_logger function that produces a global logger that may be used anywhere, but projects may also freely instantiate additional loggers as needed.