Question

I’ve downloaded Qt 4.8.2 library, Qt Creator 2.5.2, and manually installed MingW with w32api version 3.13 and GCC/g++ version 4.7.0.1. My OS is Windows 7 Ultimate x64.

I can create a sample “Plain C++ project” in Qt Creator; compile and run that console application using g++ without any issue.

But I cannot run a Qt application. I used Qt Creator, created a dummy Qt Application using Creator’s “Qt Gui Application” template. The project can be compiled successfully, without any error or warning. But the binary keeps crashing when I try to run (both from Qt Creator and Windows Explorer) it. Both debug and release builds crash. It crashes even before showing main window.

MingW is installed in C:\MingW and C:\MingW\bin is in PATH. Qt is installed in C:\Qt\4.8.2 and C:\Qt\4.8.2\bin is in PATH.

I analyzed generated exe of the Qt Gui Application output with Dependency Walker and found that it found all required DLLs:

• c:\windows\system32\KERNEL32.DLL
• c:\windows\system32\MSVCRT.DLL
• c:\mingw\bin\LIBGCC_S_DW2-1.DLL
• c:\mingw\bin\LIBSTDC++-6.DLL
• c:\qt\4.8.2\bin\QTCORE4.DLL
• c:\qt\4.8.2\bin\QTGUI4.DLL

So, what’s causing the runtime crash?

EDIT

I also tried Qt’s example projects: 2dpainting and addressbook – both crashed when they were launched.

Answer 1

You should build Qt with the MinGW compiler you’re using to build your application. GCC is generally less sensitive to binary compatibility issues than MSVC is, but Qt is a big, complex framework library. If anything would expose those kinds of issues, Qt would probably be on the short list.

Building Qt is pretty straightforward, but it takes a lot of time and there always seems to be two or three patches I need to make to get things to build successfully.

The last time I built Qt (4.7.3) with MinGW, I had to make the following patches – I’m not sure whether they will still apply to Qt 4.8:

• make sure not to enable C++11 mode in the compiler – there are several macros with concatenated string literals that break under the new C++11 extended literal syntax

• there is a problem with how some distributions of MinGW incorporate the Microsoft extensions to float.h – I had to sometimes had to add the line:

  #include_next <float.h>
  

  to the end of the MinGW-specific float.h so the generic GCC float.h would get processed properly. I had to do this for nuwen 4.7.0 lib/gcc/i686-pc-mingw32/4.7.0/include/float.h and TDM 4.6.1 32-bit distro lib/gcc/mingw32/4.6.1/include/float.h (the 64-bit distro of TDM didn’t need this patch).

• patch qmake\Makefile.win32-g++ and qmake\Makefile.win32-g++-sh to remove the -static-libstdc++ option that GCC doesn’t recognize (and now errors out on instead of ignores)

• patch mkspecs/win32-g++/qmake.conf to move the -Wl, in the QMAKE_LFLAGS_EXCEPTIONS_ON macro to its proper place in QMAKE_FLAGS:

  QMAKE_LFLAGS        = -Wl,-enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc
  QMAKE_LFLAGS_EXCEPTIONS_ON = -mthreads
  

• copy make.exe to mingw32-make.exe in MinGW’s bin directory if there’s not already a mingw32-make.exe

Then building Qt consists of:

  set QTDIR=<location of Qt source directory>  # where configure.exe is
  set PATH=%QTDIR%\bin;c:\MinGW\bin;%PATH%
  set INCLUDE=
  set LIB=
  cd %QTDIR%

  mingw32-make confclean    # (this should fail the first time, since there's nothing to clean)
  configure.exe -opensource -debug-and-release -nomake examples -nomake demos -nomake tests -platform win32-g++  # and accept the GPL license
  mingw32-make

This takes a while… hopefully nothing else will need patching.