in slf4j-to-log4j-api/src/main/java/org/apache/logging/slf4j/Log4jMarkerFactory.java [45:55]
public Marker getMarker(final String name) {
if (name == null) {
throw new IllegalArgumentException("Marker name must not be null");
}
final Marker marker = markerMap.get(name);
if (marker != null) {
return marker;
}
final org.apache.logging.log4j.Marker log4jMarker = MarkerManager.getMarker(name);
return addMarkerIfAbsent(name, log4jMarker);
}