When I compile an example of Qt, this message appears to me and can not be solved:
Project ERROR: Cannot run compiler 'g++'. Maybe you forgot to setup the environment? 15:22:23: The process "C:\Qt.9.1\mingw53_32\bin\qmake.exe" exited with code 3. Error while building/deploying project mapviewer (kit: Desktop Qt 5.9.1 MinGW 32bit) When executing step "qmake"
The problem is that you have not installed the c ++ compiler ( g++ ) or at least you do not have it in the path PATH which is where you get the executables that you can use from anywhere. The most likely is that you are using windows because in linux / unix this is done automatically. If you have installed gcc (GNU compiler collection that must include g ++) what you have to do is assign to PATH the path where the g ++ compiler is located. If you have not installed it, you have to download and install it. You can check at any time if you have it installed and in the PATH environment variable with write to the console: g++ --version . something like this should come out:
$ g++ --version
g++ (Debian 4.9.2-10) 4.9.2
Copyright (C) 2014 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.
As I see from your question I see that you have installed mingw, which should be what installs you by default qt. So what you should do is look in the bin folder that should be within mingw by the g ++ compiler and assign it to PATH where you find it. Check well it may not be in the same bin folder where it was qmake but in another bin