Message Filtering

Message Filtering and Callbacks

logme supports fine-grained control over message emission.

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Release Logging

By default, logging may be disabled in Release builds.

To force-enable logging in Release, define the macro:

• LOGME_INRELEASE

When LOGME_INRELEASE is defined, logging calls remain active in Release builds and messages follow the same filtering and routing pipeline as in Debug.

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Condition Callback (Global Filter)

logme provides a global condition callback that runs before any message processing. It can be installed via:

Logme::Instance->SetCondition(...);

Behavior:

• The default condition always returns true.
• The condition callback is evaluated before formatting and routing.
• If the callback returns false, the message is discarded immediately.

Typical uses:

• Temporarily muting all logging in the application
• Suppressing logs for specific threads
• Implementing dynamic runtime policies (e.g., based on environment or state)

Because the condition callback runs early, it is an efficient way to pause or block logging without changing channel configuration.

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Override-Based Filtering (Rate / Count Limiting)

In addition to the global condition callback, logme supports dropping messages based on override rules.

Overrides can be used to:

• Limit how often a message is allowed to appear (rate limiting)
• Limit how many times a message is allowed to appear (count limiting)

If an override limit is exceeded, the message is discarded before formatting, routing, or delivery to any backend, including file backends.

Example: One-time message

The OneTime example demonstrates that even if the application attempts to log the same message 1000 times, it will appear only once when an override like LOGME_ONCE4THIS is used:

LogmeW(LOGME_ONCE4THIS, "something went wrong!!!");

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Performance Notes

• When logging is disabled at build time, the cost of logging calls (including filtering callbacks) is eliminated.
• When enabled (including Release builds via LOGME_INRELEASE), the pipeline is designed to filter messages as early as possible to keep overhead low.