Question 1

fmtlog vs spdlog: which is faster?

Accepted Answer

fmtlog has lower latency (nanoseconds vs microseconds) and higher throughput than spdlog, but requires explicit polling for asynchronous logging, whereas spdlog handles threading automatically.

Question 2

How to set up fmtlog in a multi-threaded application?

Accepted Answer

Call fmtlog::poll() periodically from a single thread, or use fmtlog::startPollingThread(interval) to create a background thread. Each logging thread gets its own queue to avoid contention.

Question 3

Does fmtlog support log file rotation?

Accepted Answer

No, fmtlog does not have built-in log rotation. You must implement custom file management or periodically call fmtlog::setLogFile() to switch files manually.

Question 4

What happens when the log queue is full?

Accepted Answer

By default, logs are dropped, but you can define FMTLOG_BLOCK=1 to block or set a callback with fmtlog::setLogQFullCB() to handle overflow, as explained in the performance section.

Question 5

Can fmtlog output to syslog?

Accepted Answer

Not directly, but you can use fmtlog::setLogCB() to register a callback function that forwards log messages to syslog or other external systems in real-time.

Question 6

How to reduce memory overhead in fmtlog?

Accepted Answer

Use FMTLOG_ONCE macros for infrequent logs to avoid static table entries, or disable runtime level checks with FMTLOG_NO_CHECK_LEVEL to reduce code size, as noted in the README.

fmtlog

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