add log4cplus

libs/log4cplus/README

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+Short Description
+=================
+
+log4cplus is a simple to use C++ logging API providing thread-safe,
+flexible, and arbitrarily granular control over log management and
+configuration.  It is modeled after the Java log4j API.
+
+
+Latest Project Information
+==========================
+
+The latest up-to-date information for this project can be found at
+http://log4cplus.sourceforge.net.  Please submit bugs, patches,
+feature requests, etc. there.
+
+
+Current Status
+==============
+
+This library has now reached "Production" status.
+
+
+Tested on the following platforms
+=================================
+
+- Linux/AMD64 with GCC 4.1.2 and 4.3.2
+- FreeBSD/i386 and AMD64 with GCC 3.4.6, 4.2.1 and 4.3.3
+- Windows XP with MS Visual C++ 8.0, 9.0 and 10.0
+- OpenSolaris 5.11 with Sun C++ 5.10 SunOS_i386 128229-02 2009/09/21,
+  with -library=stlport4
+
+
+Notes
+=====
+
+Cygwin/MinGW
+------------
+
+Some version of GCC (3.4.x and probably some of 4.x series too) on
+Windows (both Mingw and Cygwin) produces lots of warnings of the form
+"warning: inline function 'void foo()' is declared as dllimport:
+attribute ignored."  This can be worked around by adding
+-Wno-attributes option to GCC command.  Unfortunatelly, not all
+affected version of GCC have this option.
+
+
+Threads and signals
+-------------------
+
+log4cplus is not safe to be used from async signals' handlers.  This
+is a property of most threaded programmes in general.  If you are
+going to use log4cplus in threaded application and if you want to use
+log4cplus from signal handlers then your only option is to block
+signals in all threads but one that will handle all signals.  On POSIX
+platforms, this is possible using the sigwait() call.  log4cplus
+enables this approach by blocking all signals in any threads created
+through its threads helpers.
+
+
+AIX
+---
+
+There appears to be a reentracy problem with AIX 5.3 and xlC 8 which
+can result into a deadlock condition in some curcumstances. It is
+unknown whether the problem manifests with other versions of either
+the OS or the compiler, too. The problem was initially reported in a
+bug report #3056687 ([1]).
+
+The core of the problem is that IBM's/xlC's standard C++ IOStreams
+implementation uses global non recursive lock to protect some of its
+state. The application in the bug report was trying to do logging
+using log4cplus from inside overflow() member function of a class
+derived from std::streambuf class. log4cplus itself uses
+std::ostringstream. This resulted into an attempt to recursivly lock
+the global non recursive lock and a deadlock.
+
+[1] <https://sourceforge.net/tracker/?func=detail&aid=3056687&group_id=40830&atid=429073>
+
+
+Unsupported compilers
+---------------------
+
+log4cplus does not support too old and broken C++ compilers:
+
+- Visual C++ prior to 7.1
+- GCC prior to 3.2
+- All Borland/CodeGear/Embarcadero C++ compilers
+
+
+Unsupported platforms
+---------------------
+
+log4cplus requires some minimal set of C and/or C++ library
+functions. Some systems/platforms fail to provide these functions and
+thus log4cplus cannot be supported there:
+
+- Windows CE - missing implementations of <time.h> functions
+
+
+License
+=======
+
+This library is licensed under the Apache Public License 2.0 and two
+clause BSD license.  Please read the included LICENSE file for
+details.