Compiling Qt5 hello world .cpp file under Windows using MinGW-w64 gives "undefined reference" error

Question

When I run make to compile the Makefile produced by cmake, to compile an hello world example of a Qt5 application, the compilation fails with the following error:

Why is the compilation failing?

(details of what exactly I'm trying to do follow)

---

I'm under Windows 10, using the Qt5.5 binaries downloaded from Qt official website, mingw-w64 gcc and g++ shipped with WinBuilds, and cmake v3.6 downloaded from the official website and installed with the Windows win64-x64 Installer.

I'm trying to compile the following hello world test file, provided in Qt5's official wiki:

#include <QCoreApplication>

int main(int argc, char *argv[])
{
    QCoreApplication app (argc, argv);

    return app.exec();
}

The Makefile is built successfully using the command cmake -G "MinGW Makefiles" .. from a folder called build inside the directory containing the .cpp file. The following CMakeLists.txt file (taken from Qt5's cmake wiki page, with the addition of the specification of the CMAKE_PREFIX_PATH variable, which is required as for example discussed in this SO post) was used:

cmake_minimum_required(VERSION 2.8.11)

SET(CMAKE_C_COMPILER C:/WinBuilds/bin/x86_64-w64-mingw32-gcc-4.8.3.exe)
SET(CMAKE_CXX_COMPILER C:/WinBuilds/bin/x86_64-w64-mingw32-g++-4.8.3.exe)

project(testproject)

set(CMAKE_INCLUDE_CURRENT_DIR ON)
set(CMAKE_AUTOMOC ON)
#set(CMAKE_PREFIX_PATH "C:/WinBuilds/lib64/cmake")
set(CMAKE_PREFIX_PATH "C:/Qt/5.5/mingw492_32/lib/cmake")

find_package(Qt5Widgets)

add_executable(testfile WIN32 test.cpp)

target_link_libraries(testfile Qt5::Widgets)

(I did not use the cmake shipped with Qt5 as that did not work).

Now, the problem arises when I run make (or more precisely, mingw32-make, again shipped with WinBuilds) on the Makefile produced by cmake. When I do this, the compilation fails with the following error (same one showed in the screenshot above):

CMakeFiles\testfile.dir/objects.a(test.cpp.obj):test.cpp:(.text+0x35): undefined reference to `__imp__ZN16QCoreApplicationC1ERiPPci'
CMakeFiles\testfile.dir/objects.a(test.cpp.obj):test.cpp:(.text+0x3e): undefined reference to `__imp__ZN16QCoreApplication4execEv'
CMakeFiles\testfile.dir/objects.a(test.cpp.obj):test.cpp:(.text+0x50): undefined reference to `__imp__ZN16QCoreApplicationD1Ev'
CMakeFiles\testfile.dir/objects.a(test.cpp.obj):test.cpp:(.text+0x67): undefined reference to `__imp__ZN16QCoreApplicationD1Ev'
c:/winbuilds/bin/../lib64/gcc/x86_64-w64-mingw32/4.8.3/../../../../x86_64-w64-mingw32/bin/ld.exe: CMakeFiles\testfile.dir/objects.a(test.cpp.obj): bad reloc address 0xc in section `.xdata'
c:/winbuilds/bin/../lib64/gcc/x86_64-w64-mingw32/4.8.3/../../../../x86_64-w64-mingw32/bin/ld.exe: final link failed: Invalid operation
collect2.exe: error: ld returned 1 exit status
CMakeFiles\testfile.dir\build.make:127: recipe for target 'testfile.exe' failed
mingw32-make[2]: *** [testfile.exe] Error 1
CMakeFiles\Makefile2:66: recipe for target 'CMakeFiles/testfile.dir/all' failed
mingw32-make[1]: *** [CMakeFiles/testfile.dir/all] Error 2
Makefile:82: recipe for target 'all' failed
mingw32-make: *** [all] Error 2

Why is the compilation failing?

A similar undefined reference error was reported in this other SO question, but the reason there seemed to be different than the present case.

Answer 1

The problem is you are using 32 bit mingw compiled Qt binaries when you are trying to build a 64 bit Qt application. You need to use 64 bit Qt binaries compiled with mingw for this to work.