[#XLOG_IS_ON_IMPL]
= XLOG&lowbar;IS&lowbar;ON&lowbar;IMPL
:mrdocs:

Expects a fully qualified LogLevel enum value&period;

== Synopsis

Declared in `&lt;folly&sol;logging&sol;xlog&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define XLOG&lowbar;IS&lowbar;ON&lowbar;IMPL(level)

----

== Description

This helper macro invokes XLOG&lowbar;IS&lowbar;ON&lowbar;IMPL&lowbar;HELPER() to perform the real log level check, with a couple additions&colon;

* If the log level is less than FOLLY&lowbar;XLOG&lowbar;MIN&lowbar;LEVEL it evaluates to false to allow the compiler to completely optimize out the check and log message if the level is less than this compile&hyphen;time fixed constant&period;
* If the log level is fatal, this has an extra check at the end to ensure the compiler can detect that it always evaluates to true&period; This helps the compiler detect that statements like XCHECK(false) never return&period; Note that XLOG&lowbar;IS&lowbar;ON&lowbar;IMPL&lowbar;HELPER() must still be invoked first for fatal log levels in order to initialize folly&colon;&colon;detail&colon;&colon;custom&colon;&colon;xlogFileScopeInfo&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *level*
| A fully qualified `folly&colon;&colon;LogLevel` value&period;
|===


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