Log17 is a small C++17 header for static logging.
Static logging is when you associate a singleton Log class with some set of message-generating code,
typically a single module or a set of grouped modules which share this Log.
It is static because the number of Logs doesn't change and hence the class can use static methods
for dispatching messages.
No object instantiation is necessary.
This library uses partial template specialization of a single class template to provide both logs and sinks.
The API comes with a built-in FILE* sink, but customizing it for other i/o (e.g. std::iostream) is rudimentary.
The FILE* sink is enough to pass in stdio, file, and popen() handles.
You can then instantiate a singleton Log classes which accept any number of other
singleton Log classes as template parameters.
These parameters act as sinks for the prior Log, allowing you to construct entire graphs
of Log objects.
For example, you can have a main application Log that's tied to a FILE*-based Log acting as a sink,
and another FILE*-based Log which writes to a file.
When you write to the application Log, it writes to both of its underlying sinks.
On top of that, you can have feature or module Log which uses the main application Log as its sink.
Each Log comes with nine levels of verbosity and can be configured by a
template parameter (and hence via preprocessor macro) or at runtime.
Using preprocessor macros as template arguments allows you to tune the verbosity of logging code
at compile time.
If you configure your Logger's verbosity at compile time, then messages that exceed its threshold
are nooped, resulting in very fast code.
Never throw away your debugging messages again!
Just put them in a "feature" Log and turn that log's verbosity down when you don't need it.