[Interest] Crash inside QOpenGLDebugLogger with Qt 5.2 / VS2012

[Roger Leigh]

On Sun, Apr 13, 2014 at 05:22:21PM +0200, Giuseppe D'Angelo wrote:
> Hello,
> 
> Il 13/04/2014 15:05, Roger Leigh ha scritto:
> >QWindowsGLContext::getProcAddress: Unable to resolve 'glGetPointerv'
> 
> This has already been reported and I've already fixed it in
> 
> > https://codereview.qt-project.org/#change,78981

Super, thanks.  Just as a suggestion, there's still a failure
path which can cause a crash here.  This fixes it:

commit 93edfda47f043172cf26baf14e40c57c0734341d
Author: Roger Leigh <rleigh at codelibre.net>
Date:   Sun Apr 13 14:59:25 2014 +0100

    QOpenGLDebugLogger: Fail initialisation if any GL functions are null
    
    QOpenGLDebugLogger::initialize() contains a GET_DEBUG_PROC_ADDRESS
    macro to obtain OpenGL function pointers.  However, it does not
    fail safely if a function pointer is null.  This can lead to program
    crashes when the pointers get used, for example glGetPointerv will
    cause a crash in QOpenGLDebugLogger::startLogging() if it is null.
    
    Remove the potential for a null OpenGL function pointer dereference in
    QOpenGLDebugLogger.

diff --git a/src/gui/opengl/qopengldebug.cpp b/src/gui/opengl/qopengldebug.cpp
index 90d062f..6b9b556 100644
--- a/src/gui/opengl/qopengldebug.cpp
+++ b/src/gui/opengl/qopengldebug.cpp
@@ -1356,7 +1356,9 @@ bool QOpenGLDebugLogger::initialize()
 #define GET_DEBUG_PROC_ADDRESS(procName) \
     d->procName = reinterpret_cast< qt_ ## procName ## _t >( \
         d->context->getProcAddress(QByteArrayLiteral( #procName )) \
-    );
+    ); \
+    if (!d->procName) \
+        return false;
 
     GET_DEBUG_PROC_ADDRESS(glDebugMessageControl);
     GET_DEBUG_PROC_ADDRESS(glDebugMessageInsert);

Your special case of glGetPointerv would also need the return false
adding on failure.

I know under normal circumstances all the functions should
resolve.  But if they don't, this ensures they won't be used
because we don't complete init and mark the logger as
initialised.

> which is going to appear in 5.3. Out of curiosity, which combination
> of GPU / drivers are you using?

I'm using an AMD Radeon HD 6850 with Catalyst
2013.1206.1603.28764 (latest stable) on Windows 7 x64 and
the same with fglrx for Linux amd64.


Regards,
Roger

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