[jira] [Created] (LOGCXX-533) cannot use log4cxx header files with clang++

["Sergei Delov (Jira)" <lo...@logging.apache.org>]

Sergei Delov created LOGCXX-533:
-----------------------------------

             Summary: cannot use log4cxx header files with clang++
                 Key: LOGCXX-533
                 URL: https://issues.apache.org/jira/browse/LOGCXX-533
             Project: Log4cxx
          Issue Type: Bug
          Components: Core
    Affects Versions: 0.11.0
         Environment: Windows 10/ Visual Studio 2019/clang++
            Reporter: Sergei Delov
             Fix For: 0.11.0


I initially reported the problem for vcpkg log4cxx package:

[https://github.com/microsoft/vcpkg/issues/19730]

Here's the report text:

---

[log4cxx] failure to compile application with clang on Windows/VC2019

We have an application that uses log4cxx.
When I compile with clang on Windows VC2019 I observe the following error:
_[...]_
_In file included from C:\vcpkg\installed\x64-windows\include\log4cxx/logger.h:30:_
_In file included from C:\vcpkg\installed\x64-windows\include\log4cxx/helpers/appenderattachableimpl.h:27:_
_In file included from C:\vcpkg\installed\x64-windows\include\log4cxx/spi/appenderattachable.h:30:_
_C:\vcpkg\installed\x64-windows\include\log4cxx\appender.h(140,1): error : explicit instantiation of 'allocator' not in a namespace enclosing 'std'_
_LOG4CXX_LIST_DEF(AppenderList, AppenderPtr);_
_^_
_C:\vcpkg\installed\x64-windows\include\log4cxx\log4cxx.h(91,45): note: expanded from macro 'LOG4CXX_LIST_DEF'_
_extern template class LOG4CXX_EXPORT std::allocator;_
_^_
_C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.27.29110\include\iosfwd(167,7): note: explicit instantiation refers here_
_class allocator;_
_^_

I found this error appears because clang compiler included with Visual Studio has _MSC_VER macro defined.
(Intel icx compiler also has _MSC_VER macro defined on Windows)

The simple fix worked for me for both compilers:
(log4cxx.h, line 81)
{code:java}
#elif defined(_MSC_VER) && !defined(__clang__) && !defined(LOG4CXX_STATIC){code}
I didn't try to compile with LOG4CXX_STATIC defined, though.

---

vcpkg folks recommended to address "upstream" team.



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