Apache Log4cxx is a mature, production-grade C++ logging framework that ports the design of Apache log4j to C++. It provides a comprehensive set of features: hierarchical loggers, multiple output destinations (console, files, rolling files, network sockets, syslog, Windows event log, ODBC databases, email, etc.), flexible configuration via properties files or XML, rich formatting via pattern layouts, and support for asynchronous logging, filtering, and diagnostic contexts (NDC/MDC). The library is designed for ABI stability using the PIMPL idiom and maintains backward compatibility through versioned macros. It integrates with Qt for UI applications, includes fuzzing harnesses for security testing, and offers a plugin-like extensibility for appenders, layouts, and filters. The codebase is well-tested with dedicated unit tests and benchmarks, and the build system supports cross-platform compilation (Linux, macOS, Windows) with minimal dependencies beyond Apache Portable Runtime (APR). Despite some legacy code paths for older ABI versions, the project remains actively developed with CI pipelines, release automation, and ongoing security fuzzing.