"Lazy" rotating_file_sink

[sbouchexbellomie-Philips]

Following #3328, the current implementation creates a file by default and the file is not deleted at shutdown if its content is empty.

Options:

1. Delete the empty file at shutdown in the rotating_file_sink implementation : Behaviour change
2. Same as 1 but with an new option : Break rotating_file_sink interface
3. Create a new lazyrotating_file_sink to lazily create the file : Code duplicate but changes may reduce this

Any idea ?

Thanks

[tt4g]

You can create a custom sink that wraps rotating_file_sink such as dist_sink (proxy pattern).
By creating internal rotating_file_sink only when the sink first receives the log message, the goal can be achieved without modifying rotating_file_sink API.

Wiki: https://github.com/gabime/spdlog/wiki/Sinks#implementing-your-own-sink

See also: #1357