[Hastur 0.15.2] Exception when creating SceneNode

[GangMan]

Hello everyone!

I just downloaded and compiled the new OGRE 0.15.2 release build and was very happy to read that the Debug-Shutdown bug was fixed.
But before I was even able to test that another problem occurred:
My application now crashes with an unhandled exception, everytime a SceneNode is created.

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Unhandled exception at 0x1040061d in PathFinderd.exe: 0xC0000005: Access violation reading location 0x0000010c.

I create SceneNodes the following way:

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SceneNode* testNode = static_cast<SceneNode*>(SceneManagerWrapper::getInstance()->getRootSceneNode()->createChild());

I wrote this singleton wrapper class so I can access my sceneManager object from every class.

The program (still) works fine, when I use 0.15.1, but with 0.15.2 I get this exception everytime I create a node.
Has anyone had a similar problem? Have I missed important changes from 0.15.1 to 0.15.2? Are SceneNodes created differently? Since I only get disassembly debug informations, debugging is not really effective but I have noticed that SceneManagerWrapper::getInstance() normally returns the SceneManager object but when getRootSceneNode() is called, the exception occurs.
Any ideas?

[Banania]

Are you sure your getInstance() method returns a proper pointer ?
This kind of error usually comes from bad pointers.

[haffax]

You can post your SceneManagerWrapper implementation and we can have a look at it. As Banania said the bad pointer is the most probable reason.

Aside: instead of creating the SceneNodes with createChild() you should create them with createChildSceneNode(). This spares you the ugly cast.

[GangMan]

Okay, hang on:

SceneManagerWrapper.h

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#ifndef SCENEMANAGERWRAPPER_H
#define SCENEMANAGERWRAPPER_H

#include "Ogre.h"

using namespace Ogre;

class SceneManagerWrapper
{
public:
    /**
     *	Initialises the wrapper by passing on the root node. It is used for
     *  retrieving a scene manager
     */
    static void init(Root* root);

    /**
     *	Returns a single instance of the scene manager. It is the only one
     *  available through out the whole application to avoid inconsitencies.
     */
    static SceneManager* getInstance();
private:
    /// The scene manager that manages how the scene is rendered.
    static SceneManager* mSceneManager;
};

#endif // SCENEMANAGERWRAPPER_H

SceneManagerWrapper.cpp

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#include "SceneManagerWrapper.h"

void SceneManagerWrapper::init(Root* root) {
    mSceneManager = root->getSceneManager(ST_GENERIC);
}

SceneManager* SceneManagerWrapper::getInstance() {
    return mSceneManager;
}

SceneManager* SceneManagerWrapper::mSceneManager = 0;

To create a SceneManager, "init()" should be called in the Application class, passing on the root-object. getInstance returns the sceneManager.
I understand the idea with the bad pointer but I wonder why it worked with 0.15.1...

[sinbad]

Nothing has changed in 0.15.2 regarding the creation of scene nodes, so I suspect something else has gone awry during your upgrade. It's clearly a null pointer - the question is where; perhaps you could just step your debugger through the sub-parts of that failing line and find out which part is null.

[SpannerMan]

This is just a guess ( sill learning myself ), but shouldnt

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SceneManager* PathFinderSceneManagerWrapper::mSceneManager = 0;

Be

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SceneManager* SceneManagerWrapper::mSceneManager = 0;

[GangMan]

SpannerMan, you're of course right. I used PathFinder... in my Application but removed it from the codesamples not to confuse anyone. But it seems like I forget to replace this one.

I corrected the code above.

I'm currently rebuilding OGRE to see if there were any warnings I might missed. I compiled it without checking the warnings - maybe the problem is related to building OGRE.

[Robomaniac]

try moving the last line to make it right below the header, it might be overriding the value after its set (probably not,b ut you never know )

[GangMan]

Okay, I rebuilt OGRE and looked through the warnings. Besides all the conversion warnings I got this one when Linking OgreMain in Debug Configuration (warning also occurs for Relase config but since I'm only using Debug atm, it shouldn't matter).

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LINK : warning LNK4098: defaultlib 'LIBC' conflicts with use of other libs; use /NODEFAULTLIB:library

Is this serious? Could this be responsible for the error? Is something linked wrong?

Additionally, I saw something, that doesen't belong to this problem, but I'll mention it here anyway: When zlib is linked, the following errors occur:

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zlib.lib(adler32.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(crc32.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(zutil.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(inflate.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(infblock.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(inftrees.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(infcodes.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(infutil.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info
zlib.lib(inffast.obj) : warning LNK4099: PDB 'vc60.pdb' was not found with '..\..\Dependencies\lib\Debug\zlib.lib' or at 'd:\Programme\ogrenew\OgreMain\lib\Debug\vc60.pdb'; linking object as if no debug info

I know, these errors have anything to do with the problem, but why is OGRE looking for vc6 pdbs even though I'm using VS7.1?

[sinbad]

None of these are problems, you can ignore them. For simplicity, the dependencies were built with VC6 so they are compatible with all versions of VC. In 1.0.0 I'll probably be distributing 2 separate versions and you won't get the warnings.

Your best bet is really the debugger. You need to decompose that call and find out which one is giving you a null pointer.

[GangMan]

Your best bet is really the debugger. You need to decompose that call and find out which one is giving you a null pointer.

Okay. I have to admit, I'm not an expert, when it comes to debugging. So please forgive me the question, but how can I effectively debug an application? Whenever I set a breakpoint at

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SceneNode* testNode = static_cast<SceneNode*>(SceneManagerWrapper::getInstance()->getRootSceneNode()->createChild());

and continue via "Step into" I can step into my own wrapper but then, when it comes to getRootSceneNode() or createChild() I have no access to any sources. Am I right, that this is because I just include the OgreMain_d.lib and not the whole sources in my project? But if so, how can I effectively find out, where the application produces a null pointer?

I tried to split up the node creation into three parts:

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SceneManager* sceneManager = SceneManagerWrapper::getInstance();
SceneNode* rootNode = sceneManager->getRootSceneNode();
SceneNode* childNode = static_cast<SceneNode*>(rootNode->createChild());

sceneManager and rootNode are created, both objects are not null. But wenn createChild() is called, the exception is thrown. So I guess, something goes wrong inside createChild(). Is there a way to find out?

[sinbad]

It sounds like you don't have the Ogre source on your machine, or you've copied the Ogre libraries from some other machine where the link to the debugging information, which is in the .pdb file, is missing. You should be able to step into the Ogre code (after all, we do provide a full source release).

There's nothing in createChild which should cause a crash unless you have some serious incompatibilities with your libs I think. Are you definitely using OgreMain_d.dll in debug mode?

[GangMan]

Okay, I found the problem. I tried to avoid placing my executable into the Common/bin folder. Therefore I had VS create it in the path of my application and copied the necessery DLLs into that directory as well. Somehow, I totally forgot about that, when upgrading to 0.15.2, don't ask me why. Anyway, I placed the correct dlls into that directory and everything works fine again. I can also debug into Ogre files now again. Kinda embarrassing...

sinbad (and of course all the others), thanks a lot for helping. I'm really sorry I wasted your time with this eventually simple and stupid issue.
The community here is really great since people are always trying to help - even if the problems are plain and simple.