Build ends up in error with latest compiler suite

[alpytron]

Hi, It seems there is an issue with latest compiler and it's not possible to link project. I'm getting the following error:

$ make
Scanning dependencies of target modmqttsrv
[  5%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/modbus_client.cpp.o
[ 10%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/modbus_context.cpp.o
[ 15%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/modbus_messages.cpp.o
[ 20%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/modbus_thread.cpp.o
[ 25%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/modmqtt.cpp.o
[ 30%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/mosquitto.cpp.o
[ 35%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/mqttclient.cpp.o
[ 40%] Building CXX object libmodmqttsrv/CMakeFiles/modmqttsrv.dir/mqttobject.cpp.o
[ 45%] Linking CXX shared library libmodmqttsrv.so
[ 80%] Built target modmqttsrv
[ 90%] Built target stdconv
Scanning dependencies of target modmqttd
[ 95%] Building CXX object modmqttd/CMakeFiles/modmqttd.dir/main.cpp.o
[100%] Linking CXX executable modmqttd
/usr/bin/c++     CMakeFiles/modmqttd.dir/main.cpp.o  -o modmqttd  -Wl,-rpath,/home/alpy/mqmgateway/libmodmqttsrv: ../libmodmqttsrv/libmodmqttsrv.so.1.0.0 -lmosquitto /usr/lib/x86_64-linux-gnu/libyaml-cpp.so.0.6.2 /usr/lib/x86_64-linux-gnu/libboost_log.so.1.71.0 /usr/lib/x86_64-linux-gnu/libboost_program_options.so.1.71.0 -lmodbus -lpthread /usr/lib/x86_64-linux-gnu/libboost_chrono.so.1.71.0 /usr/lib/x86_64-linux-gnu/libboost_date_time.so.1.71.0 /usr/lib/x86_64-linux-gnu/libboost_filesystem.so.1.71.0 /usr/lib/x86_64-linux-gnu/libboost_regex.so.1.71.0 /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.71.0 /usr/lib/x86_64-linux-gnu/libboost_atomic.so.1.71.0 -lpthread 
/usr/bin/ld: ../libmodmqttsrv/libmodmqttsrv.so.1.0.0: undefined reference to `modmqttd::MsgRegisterPoll::INVALID_REFRESH'
collect2: error: ld returned 1 exit status
make[2]: *** [modmqttd/CMakeFiles/modmqttd.dir/build.make:97: modmqttd/modmqttd] Error 1
make[1]: *** [CMakeFiles/Makefile2:185: modmqttd/CMakeFiles/modmqttd.dir/all] Error 2
make: *** [Makefile:130: all] Error 2

I could fix it by adding -DCMAKE_CXX_STANDARD="17" to cmake command line, so the full shell command was this: $ cmake -DWITHOUT_TESTS=1 -DCMAKE_INSTALL_PREFIX:PATH=/usr -DCMAKE_CXX_STANDARD="17"

This fixes the 'static constexpr' linking issue. Please update documentation (README.md).

[BlackZork]

Hi and thanks for this report. What is your compiler version?

[alpytron]

Hi, This is the output of version queries:

$ cmake --version
cmake version 3.16.3

$ make --version
GNU Make 4.2.1
Built for x86_64-pc-linux-gnu

$ g++ --version
g++ (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0

$ gcc --version
gcc (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0

$ ld --version
GNU ld (GNU Binutils for Ubuntu) 2.34

[BlackZork]

I've added fix in 9cfa2d1608. I do not have gcc 9.x, so I cannot test it. It would be great if you could confirm if it works for you. Thanks!

[alpytron]

It works now, thanks for the fix.

However there was an other issue with CMakeLists.txt which caused build failure if catch2 was not installed. Even if I added -DWITHOUT_TESTS=1 cmake was still trying to process content of folder 'unittests', so it ended up in error, missing catch2 library. For a quick and dirty workaround I commented out the following 2 lines:

#add_dependencies(tests stdconv)

#add_subdirectory(unittests ${build_unittests})

After this the build was successful.

[BlackZork]

Fixed in ab55badbd73. Thanks!

[alpytron]

Perfect! Thanks.