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c++qtmingwqt5qtgui

Compile time error from a Qt file: expected unqualified-id before ')' token

Porting my project from Qt4 to Qt5.1, I get this error from a Qt file:

C:\Qt\Qt5.1.1\5.1.1\mingw48_32\include\QtGui\qopenglversionfunctions.h:785: error: expected unqualified-id before ')' token
     void (QOPENGLF_APIENTRYP MemoryBarrier)(GLbitfield barriers);
                                           ^

This is the chain of defines:

#define QOPENGLF_APIENTRYP QOPENGLF_APIENTRY *
#define QOPENGLF_APIENTRY APIENTRY
#define APIENTRY WINAPI
#define WINAPI __stdcall

I noticed that the "MemoryBarrier" token is present in the libQt5OpenGLExtensionsd.a library. Should I include it, even if in the original Qt4 project nothing related to OpenGL was used?

Platform:
Windows 7
MinGW 4.8
Qt 4.8 --> Qt 5.1

Solution

  • I noticed that the "MemoryBarrier" token is present in the libQt5OpenGLExtensionsd.a library. Should I include it, even if in the original Qt4 project nothing related to OpenGL was used?

    No, those are not related. OpenGLExtension is compiled after QtGui.

    What you are hitting unfortunately is that there is a MemoryBarrier() already defined on Windows, and hence there is a clash for that and what qt is having. You can find the official Windows documentation for that:

    http://msdn.microsoft.com/en-us/library/windows/apps/ms684208(v=vs.85).aspx

    I have just discussed this with Gunnar, the QtGui maintainer, and I am planning to submit a change to Gerrit to address your issue.

    We had used something like this in our project a couple of years ago when we were writing thread-safe singletons based on QtCore:

    #if defined __GNUC__ && __GNUC__ >= 4 && __GNUC_MINOR__ >= 4    
#define __MEMBARRIER __sync_synchronize();  
#elif defined _MSC_VER && defined _WIN64    
#define __MEMBARRIER MemoryBarrier();   
#else   
#define __MEMBARRIER
#endif

    Qt may need to check ifdef MINGW/GCC/VERSION and undef the MemoryBarrier define.

    EDIT: This was fixed about half a year ago. See the following Gerrit review and the corresponding bug report for details:

    https://codereview.qt-project.org/#change,68156

    and

    https://bugreports.qt.io/browse/QTBUG-34080

    So, update to Qt 5.2.0 and it will work. Failing that, you can try to backport it.