compile failure with AsyncBuffer

[rm5248]

It's not immediatetly obvious to me as to why this is broken, but g++ 12.2 on Debian doesn't compile cleanly:

robert@debian:~/logging-log4cxx/build$ cmake ..
-- The CXX compiler identification is GNU 12.2.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PkgConfig: /usr/bin/pkg-config (found version "1.8.1") 
-- Checking for module 'apr-1'
--   Found apr-1, version 1.7.2
-- Found APR: /usr/lib/x86_64-linux-gnu/libapr-1.so  
-- Checking for module 'apr-util-1'
--   Found apr-util-1, version 1.6.3
-- Found APR-Util: /usr/lib/x86_64-linux-gnu/libaprutil-1.so;/usr/lib/x86_64-linux-gnu/libldap.so;/usr/lib/x86_64-linux-gnu/liblber.so  
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE  
-- Looking for C++ include locale
-- Looking for C++ include locale - found
-- Looking for mbsrtowcs
-- Looking for mbsrtowcs - found
-- Looking for wcstombs
-- Looking for wcstombs - found
-- Looking for fwide
-- Looking for fwide - found
-- Looking for syslog
-- Looking for syslog - found
-- Looking for pthread_sigmask
-- Looking for pthread_sigmask - found
-- Looking for pthread_self
-- Looking for pthread_self - found
-- 
-- 
-- Log4cxx configuration summary:
-- 
--   C++ compiler .................... : /usr/bin/c++
--   C++ features requested: ......... : 20
--   Build shared library ............ : ON
--   Build tests ..................... : ON
--   Build examples................... : ON
--   Build fuzzers.................... : OFF
--   Build site ...................... : OFF
--   Install prefix .................. : /usr/local
--   log4cxx library name ............ : log4cxx
--   log4cxx namespace ............... : log4cxx
--   log4cxx char API ................ : ON
--   log4cxx wchar API ............... : ON
--   log4cxx unichar API ............. : OFF
--   log4cxx char type ............... : utf-8
--   character encoding .............. : utf-8
--   Networking support .............. : ON
--   DOMConfigurator support ......... : ON
--   Qt support ...................... : OFF
--   LOG4CXX_XXXX_ASYNC macros ....... : ON
--   LOG4CXX_XXXX_FMT_ASYNC macros ... : OFF
-- C++ version and Boost settings:
--   Prefer boost: ................... : OFF
--   make_unique implementation :..... : std::make_unique
--   filesystem implementation ....... : std::filesystem
--   format implementation ........... : fmt::format
--   thread_local support? ........... : TRUE
-- Applications required for tests:
--   zip ............................. : /usr/bin/zip
--   sed ............................. : /usr/bin/sed
--   gzip ............................ : /usr/bin/gzip
-- Available appenders:
--   Async Appender .................. : ON
--   ODBC Appender ................... : OFF
--   DB Appender ..................... : ON
--   SMTP Appender ................... : OFF
--   XMLSocketAppender ............... : ON
--   SyslogAppender .................. : ON
--   Using syslog.h .................. : ON
--   TelnetAppender .................. : ON
--   ConsoleAppender ................. : ON
--   FileAppender .................... : ON
--   RollingFileAppender ............. : ON
--   MultiprocessRollingFileAppender . : OFF
-- Available layouts:
--   HTMLLayout ...................... : ON
--   JSONLayout ...................... : ON
--   PatternLayout ................... : ON
--   SimpleLayout .................... : ON
--   XMLLayout ....................... : ON
--   FMTLayout ....................... : OFF
-- Configuring done
-- Generating done
-- Build files have been written to: /home/robert/logging-log4cxx/build
robert@debian:~/logging-log4cxx/build$ make
[  1%] Building CXX object src/main/include/CMakeFiles/log4cxx-include.dir/empty-lib-stub.cpp.o
[  1%] Linking CXX static library liblog4cxx-include.a
[  1%] Built target log4cxx-include
[  1%] Building CXX object src/main/cpp/CMakeFiles/log4cxx.dir/action.cpp.o
[  1%] Building CXX object src/main/cpp/CMakeFiles/log4cxx.dir/andfilter.cpp.o
In file included from /home/robert/logging-log4cxx/src/main/include/log4cxx/logger.h:26,
                 from /home/robert/logging-log4cxx/src/main/include/log4cxx/spi/loggingevent.h:23,
                 from /home/robert/logging-log4cxx/src/main/include/log4cxx/spi/filter.h:23,
                 from /home/robert/logging-log4cxx/src/main/include/log4cxx/filter/andfilter.h:21,
                 from /home/robert/logging-log4cxx/src/main/cpp/andfilter.cpp:18:
/home/robert/logging-log4cxx/src/main/include/log4cxx/helpers/asyncbuffer.h: In member function ‘log4cxx::helpers::AsyncBuffer& log4cxx::helpers::AsyncBuffer::operator<<(const T&)’:
/home/robert/logging-log4cxx/src/main/include/log4cxx/helpers/asyncbuffer.h:87:39: error: static assertion failed: operator<<(std::ostream&) overload must be provided
   87 |                         static_assert(false, "operator<<(std::ostream&) overload must be provided");
      |                                       ^~~~~
/home/robert/logging-log4cxx/src/main/include/log4cxx/helpers/asyncbuffer.h: In member function ‘log4cxx::helpers::AsyncBuffer& log4cxx::helpers::AsyncBuffer::operator<<(const T&&)’:
/home/robert/logging-log4cxx/src/main/include/log4cxx/helpers/asyncbuffer.h:142:39: error: static assertion failed: operator<<(std::ostream&) overload must be provided
  142 |                         static_assert(false, "operator<<(std::ostream&) overload must be provided");
      |                                       ^~~~~
make[2]: *** [src/main/cpp/CMakeFiles/log4cxx.dir/build.make:90: src/main/cpp/CMakeFiles/log4cxx.dir/andfilter.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1352: src/main/cpp/CMakeFiles/log4cxx.dir/all] Error 2
make: *** [Makefile:146: all] Error 2

I can get around the problem by setting the C++ standard to 17

[swebb2066]

Could you try it with GCC 12.5 which is the most recent GCC 12?

[rm5248]

I can try to compile it later, but I'm more concerned with building out of the box without needing to install a custom compiler.

This is the latest version able to be installed thru the Debian repos:

robert@debian:~/logging-log4cxx/build$ g++ --version
g++ (Debian 12.2.0-14+deb12u1) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Two thoughts:

• this could be related to the __cpp_concepts check, there are two versions: 201907L and 202002L, we use the second one
• it could be a GCC bug in the 12.x series. I have had to do some checks before to see what compiler version is being used and turn on/off certain code. The __GNUC__, __GNUC_MINOR__, and __GNUC_PATCHLEVEL__ macros are useful here

[rm5248]

g++ 12.5.0 also has the issue. I did a quick search for issues, but I didn't see anything obvious. Since the ubuntu builds use 13.3, I'm going to guess that this is just a GCC 12 problem and it was fixed in 13.

I think we probably want to do something like:

#if defined(__GNUC__) && __GNUC__ <= 12
#define LOG4CXX_CONCEPT_BROKEN 1
#else
#define LOG4CXX_CONCEPT_BROKEN 0
#endif

...

#if defined(__cpp_concepts) && 202002 <= __cpp_concepts && !LOG4CXX_CONCEPT_BROKEN

thoughts?

[swebb2066]

Yes, good idea - I think that would save us (and users) some trouble