[jira] [Commented] (LOGCXX-528) log4cxx fails to build on Centos 7.6 / g++ 4.8.5 / Boost 1.53

["Robert Middleton (Jira)" <lo...@logging.apache.org>]

    [ https://issues.apache.org/jira/browse/LOGCXX-528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17377727#comment-17377727 ] 

Robert Middleton commented on LOGCXX-528:
-----------------------------------------

This is rather interesting.  I'm using a different VM from what I normally develop on, and setting the C++ standard to 11 allows be to recreate the issue with not detecting Boost with GCC 8.3.0 and CMake 3.13.4.  I think my normal development VM is setup to use a newer version of CMake.

The setHierarchy using weak_from_this is also rather interesting: by default, CMake will by default try to use gnu+\+11 for the standard, instead of c+\+11.  Because there are some GNU extensions activated at that point, weak_from_this is available, even though it is not actually part of the official C+\+11 standard.  You can see the [CXX_EXTENSIONS|https://cmake.org/cmake/help/latest/prop_tgt/CXX_EXTENSIONS.html#prop_tgt:CXX_EXTENSIONS] property for some more information.

Anyway, I've made a branch/PR with these fixes.  If you are able to test and see if they work on your side, that would be helpful: https://github.com/apache/logging-log4cxx/pull/66



> log4cxx fails to build on Centos 7.6 / g++ 4.8.5 / Boost 1.53
> -------------------------------------------------------------
>
>                 Key: LOGCXX-528
>                 URL: https://issues.apache.org/jira/browse/LOGCXX-528
>             Project: Log4cxx
>          Issue Type: Bug
>    Affects Versions: 0.12.0
>            Reporter: Russel Miranda
>            Assignee: Robert Middleton
>            Priority: Major
>
> With:
>  * CMake 3.13.4,
>  * g++ 4.8.5
>  * Boost 1.53.0
>  ** thread
>  ** chrono
>  ** system
>  ** date_time
>  ** atomic
>  * apr-1.6.2
>  * apr-devel-1.6.2
>  * apr-util-1.6.0
>  * apr-util-devel-1.6.0
> CMake fails to properly detect the Boost threads package, due to a link error in the test build. There is no indication of a problem at the CMake stage other than the lack of output for the shared_mutex implementation:
> {{log4cxx configuration summary:}}
>  {{Build shared library ............ : ON}}
>  {{Build tests ..................... : ON}}
>  {{Build site ...................... : OFF}}
>  {{Install prefix .................. : /usr/local}}
>  {{C++ compiler .................... : /usr/bin/c++}}
>  {{log4cxx char API ................ : utf-8}}
>  {{log4cxx wchar API ............... : ON}}
>  {{log4cxx unichar API ............. : OFF}}
>  {{logchar type .................... : utf-8}}
>  {{charset ......................... : locale}}
>  {{Using libESMTP .................. : OFF}}
>  {{ODBC library .................... : OFF}}
>  {{syslog .......................... : ON}}
>  {{Qt support ...................... : OFF}}
>  {{shared_mutex implementation ..... :}}
> This can be fixed by adding "-lboost_system" to CMAKE_CXX_FLAGS.
> After correcting the CMake problem, a make may be performed, which results in the compiler complaining that mutex is not  found in the std:: namespace in a number of places. This can be rectified by adding "#include <mutex>" to:
>  * log4cxx/src/main/include/log4cxx/helpers/appenderattachableimpl.h
>  * log4cxx/src/main/include/log4cxx/helpers/aprinitializer.h
>  * log4cxx/src/main/include/log4cxx/helpers/loglog.h
>  * log4cxx/src/main/include/log4cxx/helpers/serversocket.h
>  * log4cxx/src/main/include/log4cxx/level.h
>  * log4cxx/src/main/include/log4cxx/rolling/action.h
> This may not be a minimal set, but it was sufficient to satisfy the build.
> Once these problems have been addressed, the compiler complains that the C++ 17 feature "std::weak_from_this()" is not available. It is used in two places in log4cxx/src/main/cpp/hierarchy.cpp: line 226 and line 426.
> It may be preferable to create a local routine that stands in for "std::weak_from_this()", but I found it sufficient to just #if / #else / #endif around the single line in each location that called weak_from_this() and replace it with a two-step version similar to this:
> {{std::weak_ptr<Hierarchy> weak_handle = shared_from_this();}}
>  {{logger->setHierarchy(weak_handle);}}
> in place of the single-step:
> {{logger->setHierarchy(weak_from_this());}}
> I used the precompiler test:
> {{#if __cplusplus >= 201500L}}
> That was sufficient to differentiate my {{g++ 4.8.5}} from more modern compilers that support C++ 17, but there may be more precise ways of achieving this end - I just don't have the ability to test on anything other than {{g++ 4.8.5}}.
> After making this change the build should complete successfully, and all 60/60 tests should pass.
> NOTE: Because g++ 4.8.5 does not support std::shared_mutex and is therefore dependent on Boost thread, and Boost thread itself is dependent on Boost system, it was required to link executables using this version of log4cxx w/ Boost system as well. I suspect there may be Boost compile-time flags that might make that unnecessary, but my knowledge of Boost is not sufficient to achieve that goal.
>  



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