Pantheios is an open source C/C++ logging API library, whose design focus is performance, robustness and transparency. It claims 100% type-safety, and high efficiency.
Pantheios was forked from a proprietary logging architecture of Synesis Software in 2005, and is now completely free for use in both commercial and non-commercial activities, being licensed under the BSD license. It is platform-independent, working on UNIX (Linux, Solaris, FreeBSD), Mac OS X, and Windows (x86 and x64). It is compiler-independent, and is known to work with Borland, Metrowerks CodeWarrior, Comeau, Digital Mars, GCC, Intel, Sun Studio and Microsoft Visual C++ compilers.
Pantheios provides both C and C++ APIs. The C++ API is infinitely extensible to allowing logging of arbitrary types.
The API is designed to work with any logging transport (aka "back-end"), including existing logging libraries such as ACE and log4cxx.
Read more about Pantheios: Design Principles, Architecture, Dependencies, Criticisms, Other Languages