Ok, to pass that error in exflags for compiler used -fpermissive
now got alsa error?
../../../Desktop/juce/JUCE-LINUX/modules/juce_audio_devices/juce_audio_devices.cpp:106:30: fatal error: alsa/asoundlib.h: No such file or directory
#include <alsa/asoundlib.h>
/* Got an include error here? If so, you've either not got ALSA installed, or you've
not got your paths set up correctly to find its header files.
The package you need to install to get ASLA support is "libasound2-dev".
If you don't have the ALSA library and don't want to build Juce with audio support,
just set the JUCE_ALSA flag to 0.
You never need to qualify a constructor with the classname, e.g. "MidiMessage::MidiMessage" - I'm not even sure if that's legal C++, and the compiler is correct to complain about it.
And it's a really bad idea as a learner to use -fpermissive, it'll allow you to adopt bad habits!