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.
The latest up-to-date information for this project can be found at log4cplus.sourceforge.net. Please submit bugs, patches, feature requests, etc., there.
--enable-debugging
This option is disabled by default. This option mainly affects GCC builds but it also has some limited effect on non-GCC builds. It turns on debugging information generation, undefines NDEBUG
symbol and adds -fstack-check
(GCC).
--enable-warnings
This option is enabled by default. It adds platform / compiler dependent warning options to compiler command line.
--enable-so-version
This option is enabled by default. It enables SO version decoration on resulting library file, e.g., the .2.0.0
in liblog4cplus-1.2.so.2.0.0
.
--enable-release-version
This option is enabled by default. It enables release version decoration on the resulting library file, e.g., the -1.2
in liblog4cplus-1.2.so.2.0.0
.
--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 BSDs.
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 Unix–like 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 encoding. 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.
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. Unfortunately, not all affected version of GCC have this option.
log4cplus can use functions like _vsnprintf_s()
(Microsoft’s secure version of vsnprintf()
). MinGW tool–chains (by default) link to the system MSVCRT.DLL. Unfortunately, older systems, like Windows XP, ship with MSVCRT.DLL that lacks these functions. It is possible to compile log4cplus with MinGW tool–chains but without using the Microsoft’s secure functions by defining __MSVCRT_VERSION__
to value less than 0x900
and vice versa.
$ ../configure CPPFLAGS="-D__MSVCRT_VERSION__=0x700"
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:
TlsAlloc()
, etc., functions__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 targeted to Windows Vista or later.
log4cplus is not safe to be used from asynchronous 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 executable has many variants. 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
There appears to be a reentracy problem with AIX 5.3 and xlC 8 which can result into a deadlock condition in some circumstances. 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 #103.
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 recursively lock the global non recursive lock and a deadlock.
Some older version of this operating system might have problems linking log4cplus due to missing __tls_get_addr
in their unpatched state.
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.
The autotools and our configure.ac 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"
It is necessary to turn on C++98 mode of aCC by providing the -AA
flag:
$ ../configure --enable-threds=yes CXXFLAGS="-AA"
Haiku is supported with GCC 4+. The default GCC version in Haiku is set to version 2 (based on GCC 2.95.x). To change the default GCC version to version 4, please run setgcc gcc4
command. This is to avoid linking errors like this:
main.cpp:(.text.startup+0x54a): undefined reference to `_Unwind_Resume'
Running the command switches the current GCC version to version 4. This change is permanent and global. See also Haiku ticket #8368.
In order to use log4cplus in Qt4 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 runtime, call this function: 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 UNICODEBeware, the %s
specifier does not work the same way on Unix–like platforms 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 printf()
. On the other hand, Unix–like platforms 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 Unix–like platforms.
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 Unix–like platforms and Windows. The conversion of wchar_t
back to char
then depends on C locale.
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.
log4cplus does not support too old or broken C++ compilers:
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:
<time.h>
functionsThis library is licensed under the Apache Public License 2.0 and two clause BSD license. Please read the included LICENSE file for details.