log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java
log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JLogger.java

log4j-api/src/main/java/org/apache/logging/log4j/internal/DefaultLogBuilder.java
log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JLogBuilder.java