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. Tested on the following platforms ================================= - Linux/AMD64 with GCC 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) - Linux/AMD64 with Sun C++ 5.12 Linux_i386 2011/11/16 - Linux/AMD64 with Clang version 3.0-6ubuntu3 (tags/RELEASE_30/final) (based on LLVM 3.0) - Linux/AMD64 with Intel(R) C++ Intel(R) 64 Compiler XE for applications running on Intel(R) 64, Version 12.1 Build 20120410 - FreeBSD/AMD64 with GCC 3.4.6, 4.2.1 and 4.3.3 - Windows 7 with MS Visual C++ 10.0 - OpenSolaris 5.11 with Sun C++ 5.10 SunOS_i386 128229-02 2009/09/21, with -library=stlport4 - Solaris 5.10 with Sun C++ 5.8 2005/10/13, with -library=stlport4 - NetBSD 5.0.2/AMD64 with GCC 4.1.3 20080704 prerelease (NetBSD nb2 20081120) - OpenBSD 5.0/AMD64 with GCC 4.2.1 20070719 Configure script options ======================== --enable-debugging ------------------ This option is disabled by default. This option mainly affects GCC builds but it also has some limitted effect on non-GCC builds. It turns on debugging information generation, undefines NDEBUG symbol, adds '-fkeep-inline-functions' and '-fstack-check' (GCC). --enable-warnings ----------------- This option is enabled by default. It adds platform / compiler dependent warning options to compiler command line. --enable-profiling ------------------ This option is disabled by default. This option adds profiling information generation compiler option -pg to GCC and Sun CC / Solaris Studio builds. --enable-threads ---------------- This option is enabled by default. It turns on detection of necessary compiler and linker flags that enable POSIX threading support. While this detection usually works well, some platforms still need help with configuration by supplying additional flags to the configure script. One of the know deficiencies is Solaris Studio on Linux. See one of the later note for details. --with-working-locale --------------------- This is one of three locale and wchar_t <-> char conversion related options. It is disabled by default. It is know to work well with GCC on Linux. Other platforms generally have lesser locale support in their implementations of the C++ standard library. It is known not to work well on any *BSD. See also docs/unicode.txt. --with-working-c-locale ----------------------- This is second of wchar_t <-> char conversion related options. It is disabled by default. It is known to work well on most *NIX platforms, including recent Cygwin. --with-iconv ------------ This is third of wchar_t <-> char conversion related options. It is disabled by default. The conversion using iconv() function always uses "UTF-8" and "WCHAR_T" as source/target encodings. It is known to work well on platforms with GNU iconv. Different implementations of iconv() might not support "WCHAR_T" encoding selector. Either system provided iconv() or library provided libiconv() are detected and accepted. Also both SUSv3 and GNU iconv() function signatures are accepted. --with-qt --------- This option is disabled by default. It enables compilation of a separate shared library (liblog4cplusqt4debugappender) that implements Qt4DebugAppender. It requires Qt4 and pkg-config to be installed. 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. Windows and TLS --------------- log4cplus uses thread-local storage (TLS) for NDC, MDC and to optimize use of some temporary objects. On Windows there are two ways to get TLS: (1) using TlsAlloc() etc. functions, and (2) using __declspec(thread). While method (2) generates faster code, it has some limitations prior to Windows Vista. If log4cplus.dll is loaded at run time using LoadLibrary() (or as a dependency of such loaded library), then accessing __declspec(thread) variables can cause general protection fault (GPF) errors. This is because Windows prior to Windows Vista do not extend the TLS for libraries loaded at run time using LoadLibrary(). To allow using the best available method, log4cplus enables the method (2) by checking _WIN32_WINNT >= 0x0600 condition, when compiling log4cplus targetted to Windows Vista or later. 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. IBM's XL C/C++ compiler ----------------------- IBM's XL C/C++ compiler executable has many variants ([1]). To compile log4cplus with threading support specify one of the compiler variants that support threading using the CXX variable on configure script command line. E.g.: $ ../configure --enable-threads CXX=xlC_r [1] AIX reentrancy problem ---------------------- 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] Solaris / SunOS --------------- Some older version of this operating system might have problems linking log4cplus due to missing __tls_get_addr ([1]) in their unpatched state. [1] Solaris Studio -------------- Solaris Studio compilers' default standard C++ library is very non-standard. It seems that it is not conforming enough in, e.g., Sun C++ 5.12 Linux_i386 2011/11/16 (missing std::time_t, etc.), but it works well enough on Solaris with Sun C++ 5.8 2005/10/13. Thus log4cplus adds -library=stlport4 to the CXXFLAGS environment variable, unless a switch matching -library=(stlport4|stdcxx4|Cstd) is already present there. If you want to override the default supplied by log4cplus, just set it into CXXFLAGS on configure script command line. Solaris Studio supports the __func__ symbol which can be used by log4cplus to record function name in logged events. To enable this feature, add '-features=extensions' switch to CXXFLAGS for configure script. Subsequently, you will have to add this switch to your application's build flags as well. Solaris Studio on GNU/Linux --------------------------- The autotools and our configure.in combo does not handle Solaris Studio compiler on Linux well enough and needs a little help with configuration of POSIX threads: $ COMMON_FLAGS="-L/lib/x86_64-linux-gnu/ -L/usr/lib/x86_64-linux-gnu/ \ -mt=yes -O" $ ../configure --enable-threads=yes CC=/opt/solarisstudio12.3/bin/cc \ CXX=/opt/solarisstudio12.3/bin/CC CFLAGS="$COMMON_FLAGS" \ CXXFLAGS="$COMMON_FLAGS" LDFLAGS="-lpthread" Qt / Win32 / MSVC ----------------- In order to use log4cplus in Qt programs it is necessary to set following option: Treat WChar_t As Built in Type: No (/Zc:wchar_t-) Set this option for log4cplus project and Qt4DebugAppender project in MS Visual Studio. Remember to use Unicode versions of log4cplus libraries with Qt. It is also necessary to make clear distinction between debug and release builds of Qt project and log4cplus. Do not use log4cplus release library with debug version of Qt program or vice versa. For registering Qt4DebugAppender library at run-time call this method: log4cplus::Qt4DebugAppender::registerAppender() ; Add these lines to qmake project file for using log4cplus and Qt4DebugAppender: INCLUDEPATH += C:\log4cplus\include win32 { CONFIG(debug, debug|release) { LIBS += -LC:\log4cplus\msvc10\Win32\bin.Debug_Unicode -llog4cplusUD LIBS += -LC:\log4cplus\msvc10\Win32\bin.Debug_Unicode -llog4cplus-Qt4DebugAppender } else { LIBS += -LC:\log4cplus\msvc10\Win32\bin.Release_Unicode -llog4cplusU LIBS += -LC:\log4cplus\msvc10\Win32\bin.Release_Unicode -llog4cplus-Qt4DebugAppender } } LOG4CPLUS_*_FMT() and UNICODE ----------------------------- Beware, the %s specifier does not work the same way on *NIX as it does on Windows with Visual Studio. With Visual Studio the %s specifier changes its meaning conveniently by printing wchar_t string when used with wprintf() and char strings when used with wprintf(). On the other hand, *NIX keeps the meaning of printing char strings when used with both wprintf() and printf(). It is necessary to use %ls (C99) specifier or %S (SUSv2) specifier to print wchar_t strings on *NIX. The common ground for both platforms appears to be use of %ls and wchar_t string to print strings with unmodified formatting string argument on both *NIX and Windows. The conversion of wchar_t back to char then depends on C locale. C++11 support ------------- log4cplus contains small amount of code that uses C++11 (ISO/IEC 14882:2011 standard) language features. C++11 features are used only if C++11 support is detected during compile time. Compiling log4cplus with C++11 compiler and standard library and using it with C++03 (ISO/IEC 14882:2003 standard) application is not supported. Unsupported compilers --------------------- log4cplus does not support too old or 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 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.