Hi Robert,
Well, if you can convince me that a NULL pointer exception and a crashing,
is in any way more helpful than reporting OpenGL error code 0x502, then I
would agree with you. But in any case, if gluErrorString returning NULL
represents such a deep failure, why not report that, rather than waiting
until ostream inserter blows a wobbler and crashes the app? It gives you
nothing unless you happen to be running a debugger an can look at a stack
trace.
Chris.
----- Original Message -----
From: "Robert Osfield" <[EMAIL PROTECTED]>
To: "Chris Denham" <[EMAIL PROTECTED]>
Cc: "OpenSceneGraph Submissions" <[email protected]>
Sent: Friday, September 19, 2008 5:56 PM
Subject: Re: [osg-submissions] SceneView OpenGL error trap succeptable to
null pointer exception in OSG2.6.
Hi Chris,
If the get string is null, then it suggests that you don't have a
valid graphics context, so the error code you'd get would be complete
nonsense. Hiding this crash does nothing to help you.
Robert.
On Fri, Sep 19, 2008 at 5:35 PM, Chris Denham <[EMAIL PROTECTED]>
wrote:
Hi Robert,
Surely the purpose of the code that reports the GL error is intended to
help
users fix the problem.
It it not helpful if the application crashes while it is merely trying to
output the "pretty string" version of the error code.
My suggested change does NOT hide the bug. On the contary, it helps you
find
the bug because it tells you the error code rather than bombing out
trying
to display the error.
Chris.
----- Original Message ----- From: "Robert Osfield"
<[EMAIL PROTECTED]>
To: "Chris Denham" <[EMAIL PROTECTED]>
Cc: "OpenSceneGraph Submissions"
<[email protected]>
Sent: Friday, September 19, 2008 5:14 PM
Subject: Re: [osg-submissions] SceneView OpenGL error trap succeptable to
null pointer exception in OSG2.6.
Hi Chris,
The submission isn't problematic, but the suggestion that it might fix
a crash is, as the app is broken and is likely just to crash somewhere
else that access OpenGL. The crash you have is symptom of problem
elsewhere, the fix really is not really a fix, it's just a recording
to hide a bug elsewhere.
Robert.
On Fri, Sep 19, 2008 at 5:06 PM, Chris Denham <[EMAIL PROTECTED]>
wrote:
Hi Robert,
You may be right about the cause of the GL error as I am currently
doing
horrible things experimenting with code to try and support an SVI
display.
However, I stand by this submission, as it was not really about the
cause
of
the GL error, more about how it is reported and the re-use of the GL
error
reporting code in State.cpp.
Basically, <<gluErrorString(errorNo)<<" goes bang! if there is no error
string for the code passed in.
It seemed to me that the original code makes an assumption the return
value
of gluErrorString(errorCode) being non NULL.
An assumption that is not made by the code in State::checkGLErrors(),
so
it
makes sense to reuse that code in any case.
Hope that explains my reasoning for submitting this trivial little
change.
And it might stop an app crashing unnecessarily when it gets a GLerror
for
which there is no 'pretty string' available..
Chris.
----- Original Message ----- From: "Robert Osfield"
<[EMAIL PROTECTED]>
To: "Chris Denham" <[EMAIL PROTECTED]>; "OpenSceneGraph Submissions"
<[email protected]>
Sent: Friday, September 19, 2008 4:43 PM
Subject: Re: [osg-submissions] SceneView OpenGL error trap succeptable
to
null pointer exception in OSG2.6.
Hi Chris,
If glGetError() is crashing then it suggests that you are calling this
code from a thread that doesn't have valid graphics context, which is
a bug at the application level, rather than SceneView itself.
Robert.
On Fri, Sep 19, 2008 at 4:09 PM, Chris Denham <[EMAIL PROTECTED]>
wrote:
Just found a little problem with SceneView.cpp crashing with NULL
pointer
exception because it tried to use a NULL returned by
gluErrorString().
I noticed that there is GL error reporting code in State.cpp that
probably
should have be used here.
Mods shown below, and I have attached modified osg2.6 SceneView.cpp
//////////////////BEFORE//////////////////////
GLenum errorNo = glGetError();
if (errorNo!=GL_NO_ERROR)
{
osg::notify(WARN)<<"Warning: detected OpenGL error
'"<<gluErrorString(errorNo)<<"'"<< std::endl;
// go into debug mode of OGL error in a fine grained way to
help
// track down OpenGL errors.
state->setCheckForGLErrors(osg::State::ONCE_PER_ATTRIBUTE);
}
}
/////////////AFTER////////////////////////////
if (state->checkGLErrors("end of SceneView::draw()"))
{
// go into debug mode of OGL error in a fine grained way to
help
// track down OpenGL errors.
state->setCheckForGLErrors(osg::State::ONCE_PER_ATTRIBUTE);
}
//////////////////////////////////////////////////////
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