% log4cplus README Short Description ================= [log4cplus] is a simple to use C++11 logging API providing thread--safe, flexible, and arbitrarily granular control over log management and configuration. It is modeled after the Java log4j API. [log4cplus]: https://sourceforge.net/projects/log4cplus/ Latest Project Information ========================== The latest up-to-date information for this project can be found at [log4cplus] SourceForge project pages or [log4cplus wiki][4] on SourceForge. Please submit bugs, patches, feature requests, etc., there, or on [GitHub][13]. [4]: https://sourceforge.net/p/log4cplus/wiki/Home/ [13]: https://github.com/log4cplus/log4cplus Mission statement ================= The aim of this project is to develop log4j--like logging framework for use in (primarily) C++. One of the major design goals is to avoid huge dependencies (like Boost) in the core functionality and to use standard C++ facilities instead. Where possible, the project takes inspiration from other logging libraries, beside from log4j (e.g., from log4net, log4cxx, log4cpp). Platform support ================ [log4cplus] version 2.0 and beyond require C++11. [log4cplus] has been ported to and tested on the following platforms: - Linux/AMD64 with GCC version 6.2.0 20161005 (Ubuntu 6.2.0-5ubuntu12) - Linux/AMD64 with Clang version 3.8.1-12ubuntu1 (tags/RELEASE_381/final) - Windows/AMD64 with GCC version 4.8.2 (x86_64-posix-seh-rev3, Built by MinGW-W64 project) using CMake build system - Windows/AMD64 with GCC version 4.9.2 (tdm64-1) using CMake build system - Windows 7 with MS Visual Studio 2015 - OpenBSD 5.6/AMD64 with GCC version 4.9.0 - FreeBSD 10.1/i386 with Clang version 3.4.1 (tags/RELEASE_34/dot1-final 208032) - NetBSD 6.1.5/AMD64 with GCC version 4.9.1 - DragonflyBSD 4.0.1/AMD64 with GCC version 4.9.3 20141126 (prerelease) (FreeBSD Ports Collection) - OpenIndiana Hipster 2016.10 with GCC version 4.9.4 The testing on the above listed platforms has been done at some point in time with some version of source. Continuous testing is done only on Linux platform offered by [Travis CI][11] service. The oldest Windows version that is supported by 2.x releases is Windows Vista. The following platforms were supported by the 1.x series of [log4cplus]. They either do not have a reasonable C++11 capable compiler or have not been checked with [log4cplus] 2.x, yet: - Minix 3.3.0/i386 with Clang version 3.4 (branches/release_34) with `--disable-threads` - Linux/AMD64 with Intel Parallel Studio XE 2015, ICPC version 15.0.1 - OpenSolaris with `-library=stlport4` - Solaris with `-library=stlport4` and with `-library=Cstd`. - Solaris 5.10/Sparc - MacOS X 10.8 - MacOS X 11.4.2 - HP-UX (hppa2.0w-hp-hpux11.11) - Haiku R1 Alpha 4.1 - AIX 5.3 with IBM XL C/C++ for AIX Installation instruction ======================== Generic Autotools installation instructions are in `INSTALL` file. The following are [log4cplus] specific instructions. [log4cplus] uses Git sub-modules. Always use `--recurse-submodules` option when doing `git clone`. Configure script options ======================== `--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-symbols-visibility-options` ------------------------------------- This option is enabled by default. It enables use of compiler and platform specific option for symbols visibility. See also the [Visibility][8] page on GCC Wiki. [8]: http://gcc.gnu.org/wiki/Visibility `--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-wchar_t-support` ------------------------ This option is enabled by default. When enabled, additional binaries will be built, marked with `U` suffix in file name and compiled with `-DUNICODE=1` flag. In effect, these binaries assume that `log4cplus::tchar` is `wchar_t`. `--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. `--enable-unit-tests` --------------------- This option is disabled by default. It enables compilation of unit tests along their units. These unit tests then can be executed through `unit_tests` test executable that is built during compilation. Notes ===== Compilation ----------- On Unix--like platforms, [log4cplus] can be compiled using either autotools based build system or using CMake build system. The autotools based build system is considered to be primary for Unix--like platforms. On Windows, the primary build system is Visual Studio 2015 solution and projects (`msvc14/log4cplus.sln`). MinGW is supported by autotools based build system. CMake build system is supported as well and it should be used to compile [log4cplus] with older versions of Visual Studio or with less common compiler suites (e.g., Embarcadero, Code::Blocks, etc.). Cygwin ------ Cygwin 2.5.x has a problem[^pr64697] linking binaries that use language level thread-local storage and share thread-local variables across translation units. To avoid the issue language level thread-local storage is not used on Cygwin and traditional POSIX thread-local storage is used instead. [^pr64697]: MinGW and MSVCRT version ------------------------ [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 Microsoft's secure functions by defining `__MSVCRT_VERSION__` to value less than `0x900` and vice versa. $ ../configure CPPFLAGS="-D__MSVCRT_VERSION__=0x700" Windows and Visual Studio ------------------------- [log4cplus] uses C++11 thread and synchronization facilities. The synchronization facilities are implemented in Visual Studio C++ standard library in a way that utilizes global variables. Therefore it is impossible (due to "static initialization order fiasco") to use them outside `main()`. This issue manifests as a deadlock on exit during destruction of [log4cplus]' thread pool. To overcome this limitation, - always use `log4cplus::Initializer initializer;` as the first thing in `main()`; - never try to log from static/global objects constructors; - never try to log from static/global object destructors. Defining the `log4cplus::Initializer` instance as the first thing in `main()` ensures that [log4cplus] is initialized. More importantly, it ensures that [log4cplus] shuts down before the execution leaves the `main()` function. [log4cplus] will try to automatically initialize at process startup and/or on DLL load, and will not tear down until all `log4cplus:Initializer` instances are destroyed. Windows and rolling file Appenders ---------------------------------- On Windows, the standard C++ file streams open files in way that underlying Win32 file `HANDLE` is not open with `FILE_SHARE_DELETE` flag. This flag, beside shared delete, allows renaming files that have handles open to them. This issue manifests as error code 13 when the file needs to be rolled over and it is still open by another process. This is also [bug #167](https://sourceforge.net/p/log4cplus/bugs/167/) on SourceForge. 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 2. using `__declspec(thread)` While method (2) generates faster code, it has [some limitations prior to Windows Vista][tlsvista]. 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. [tlsvista]: http://support.microsoft.com/kb/118816/en-us Linking on Windows ------------------ If you are linking your application with DLL variant of [log4cplus], define `LOG4CPLUS_BUILD_DLL` preprocessor symbol. This changes definition of `LOG4CPLUS_EXPORT` symbol to `__declspec(dllimport)`. Android, TLS and CMake ---------------------- [log4cplus] uses thread--local storage (TLS, see "Windows and TLS" for details). On the Android platform, when [log4cplus] is being compiled using the `android/android.toolchain.cmake`, you might get errors featuring the `__emutls` symbol: global-init.cxx:268:46: error: log4cplus::internal::__emutls_t._ZN9log4cplus8internal3ptdE causes a section type conflict with log4cplus::internal::ptd To work around this issue, invoke CMake with `-DANDROID_FUNCTION_LEVEL_LINKING:BOOL=OFF` option. Threads and signals ------------------- [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 ----------------------- 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]: http://www.ibm.com/support/knowledgecenter/en/SSGH3R_12.1.0/com.ibm.xlcpp121.aix.doc/compiler_ref/tucmpinv.html 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 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][2]. 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. [2]: http://sourceforge.net/p/log4cplus/bugs/103/ Solaris / SunOS --------------- Some older version of this operating system might have problems linking [log4cplus] due to [missing `__tls_get_addr`][3] in their unpatched state. [3]: https://groups.google.com/d/msg/comp.unix.solaris/AAMqkK0QZ6U/zlkVKA1L_QcJ 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.ac` combo does not handle Solaris Studio compiler on Linux well enough and needs a little help with configuration of POSIX threads: ~~~~{.bash} $ 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" ~~~~ HP-UX with `aCC` ---------------- It is necessary to turn on C++98 mode of `aCC` by providing the `-AA` flag: $ ../configure --enable-threads=yes CXXFLAGS="-AA" HP-UX with `aCC` on IA64 ------------------------ There is a problem on IA64 HP-UX with `aCC` (HP C/aC++ B3910B A.06.20). The problem manifests as [unsatisfied symbols during linking of `loggingserver`][9]: ld: Unsatisfied symbol "virtual table of loggingserver::ClientThread" in file loggingserver.o The problem appears to be a deficiency in `aCC` and its support of `__declspec(dllexport)`. To work around this issue, add `--disable-symbols-visibility-options` to `configure` script command line: $ ../configure --disable-symbols-visibility-options \ --enable-threads=yes CXXFLAGS="-AA" [9]: http://h30499.www3.hp.com/t5/Languages-and-Scripting/Building-Log4cplus-fails-with-quot-ld-Unsatisfied-symbol-virtual/td-p/6261411#.UoHtgPmet8G Haiku ----- 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](http://dev.haiku-os.org/ticket/8368). Qt4 / Win32 / MSVC ------------------ 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 and 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\msvc14\Win32\bin.Debug_Unicode -llog4cplusUD LIBS += -LC:\log4cplus\msvc14\Win32\bin.Debug_Unicode -llog4cplus-Qt4DebugAppender } else { LIBS += -LC:\log4cplus\msvc14\Win32\bin.Release_Unicode -llog4cplusU LIBS += -LC:\log4cplus\msvc14\Win32\bin.Release_Unicode -llog4cplus-Qt4DebugAppender } } Qt / GCC -------- You might encounter the following error during compilation with `--with-qt` option: qglobal.h:943: error: ISO C++ does not support 'long long' This is caused by `-pedantic` option that [log4cplus] adds to `CXXFLAGS` when compiling with GCC. To work around this issue, add `-Wno-long-long` GCC option to `CXXFLAGS`. OpenBSD ------- OpenBSD 5.2 and earlier have a bug in `wcsftime()` function in handling of `%%` and `%N` where N is not a supported formatter. This is fixed in OpenBSD 5.3 and later. This shows as failing `timeformat_test` when [log4cplus] is compiled with `-DUNICODE` in `CXXFLAGS`. iOS support ----------- iOS support is based on CMake build. Use the scripts in `iOS` directory. The `iOS.cmake` toolchain file was originally taken from [ios-cmake] project. To build the library for iOS, being in current folder, perform the steps below. For ARMv7 architecture: $ ./scripts/cmake_ios_armv7.sh $ cmake --build ./build_armv7 --config "Release" $ cmake --build ./build_armv7 --config "Debug" For i386 architecture: $ ./scripts/cmake_ios_i386.sh $ cmake --build ./build_i386 --config "Release" $ cmake --build ./build_i386 --config "Debug" Some versions of the iOS and/or its SDK have problems with thread-local storage (TLS) and getting through CMake's environment detection phase. To work around these issues, make these changes: Edit the `iOS.cmake` file and add these two lines. set (CMAKE_CXX_COMPILER_WORKS TRUE) set (CMAKE_C_COMPILER_WORKS TRUE) Add these lines. Customize them accordingly: set(MACOSX_BUNDLE_GUI_IDENTIFIER com.example) set(CMAKE_MACOSX_BUNDLE YES) set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "iPhone Developer") set(IPHONEOS_ARCHS arm64) If you have issues with TLS, also comment out these lines: set(LOG4CPLUS_HAVE_TLS_SUPPORT 1) set(LOG4CPLUS_THREAD_LOCAL_VAR "__thread") [ios-cmake]: https://code.google.com/p/ios-cmake/ `LOG4CPLUS_*_FMT()` and UNICODE ------------------------------- Beware, 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. Unsupported compilers and platforms ----------------------------------- [log4cplus] does not support too old or broken C++ compilers. Since [log4cplus] version 2.0.0, it means it does not support any platform or compiler without decent C++11 support. - Visual Studio prior to 2015 - GCC prior to 4.8 Bug reporting instructions -------------------------- For successful resolution of reported bugs, it is necessary to provide enough information: - [log4cplus] - What is the exact release version or Git branch and revision? - What is the build system that you are building [log4cplus] with (Autotools, Visual Studio solution and its version, CMake). - Autotools -- Provide `configure` script parameters and environment variables, attach generated `config.log` and `defines.hxx` files. - CMake -- Provide build configuration (`Release`, `Debug`, `RelWithDebInfo`) and non--default `CMAKE_*` variables values. - Visual Studio -- Provide project configuration (`Release`, `Release_Unicode`, `Debug`, `Debug_Unicode`) and Visual Studio version. - Provide target OS and CPU. In case of MinGW, provide its exact compiler distribution -- TDM? Nuwen? Other? - [log4cplus] client application - Are you using shared library [log4cplus] or as static library [log4cplus]? - Is [log4cplus] linked into an executable or into a shared library (DLL or SO)? - If [log4cplus] is linked into a shared library, is this library loaded dynamically or not? - What library file you are linking your application with -- `log4cplus.lib`, `log4cplusUSD.lib`, `liblog4cplus.dll.a`, etc., on Windows? - Is your application is using Unicode/`wchar_t` or not? - Provide any error messages. - Provide stack trace. - Provide [log4cplus] properties/configuration files. - Provide a self--contained test case, if possible. 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. Contributions ============= [log4cplus] (bug tracker, files, wiki) is hosted on SourceForge, except for [log4cplus source][5], which is hosted on GitHub. This allows the project to integrate with [Travis CI][11] service offered by GitHub. [5]: https://sourceforge.net/p/log4cplus/source-code-link/ [11]: https://sourceforge.net/p/log4cplus/travis-ci/ Patches ------- Anybody can contribute to log4cplus development. If you are contributing a source code change, use a reasonable form: a merge request of a Git branch or a patch file attached to a ticket in [Bugs tracker][6] or sent to [log4cplus-devel mailing list][7]. Unless it is obvious, always state what branch or release tarball is your patch based upon. [6]: https://sourceforge.net/p/log4cplus/bugs/ [7]: mailto:log4cplus-devel@lists.sourceforge.net Formatting ---------- Please use common sense. Follow the style of surrounding code. You can use the following Emacs style that is based on Microsoft's style as a guide line: ~~~~{.commonlisp} ;; Custom MS like indentation style. (c-add-style "microsoft" '("stroustrup" (c-offsets-alist (innamespace . -) (inline-open . 0) (inher-cont . c-lineup-multi-inher) (arglist-cont-nonempty . +) (template-args-cont . +)))) ~~~~ Tools ----- ### Build system [log4cplus] supports multiple build systems (GNU Autoconf/Automake/Libtool aka Autotools, CMake and Visual Studio solution and project files). Autotools is considered the primary build system on Unix--like platforms. However, CMake should still be usable on Unix--like platforms as well. On Windows, it depends on compiler and tool-chain that you want to use. When using Visual Studio, use Visual Studio solution and project files. However, CMake build system should still work and produce useful results. When using some form of MinGW64 tool-chain, the CMake build system is considered primary and the Autotools based build system is unsupported. Use the `MinGW Makefiles` option and build with `mingw-make` (or similar). The `MSYS Makefiles` option is untested and unsupported. #### Autotools The `Makefile.am` files for this build systems are hand written. Some of them, however, are generated from `Makefile.am.tpl` and `Makefile.am.def` by [GNU Autogen][12]. This is to make adding new files to the source easier. To regenerate `Makefile.am` files, `configure` script, `testsuite` script or any other part of the Autotools build system, use the `scripts/doautoreconf.sh` script from source root directory. It will invoke all the necessary tools in the correct order. [log4cplus] closely follows Autoconf's, Automake's and Libtool's development and its master branch files are always generated using the latest available version of the tools. [12]: http://www.gnu.org/software/autogen/