[gl4java-usergroup] Re: GL4Java continuous crashes

[Sven G. <sgo...@ja...>]

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On Tue, 14 Nov 2000, Max Gilead wrote:
> Hi!
>
> I'm experiencing continuous JVM crashes because of GL4Java (GLFuncJauJNI
> is listed on top of program trace each time). The problem is that those
> crashes are semi-random ie. I change something insignificant (like
> variable initial value or even launch another application like currently
> Netscape) and problem disappears. I don't have any idea how this
> behavior can be reproduced but it's *very* tiresome and it occures
> *very* often (several times per hour - note that I have to wait for
> 130MB core to be dumped each time - it takes time).
>
> Again - I don't have to change *anything* in application (but it
> sometimes works too), just change system environment a little and it
> 'solves' problem.
>
> If anyone has ANY ideas what should I do, I would be VERY grateful.
>

Well - this looks like a stack overflow behavior !
I guess it is NOT GL4Java's native libraries, but I am not shure !

GL4Java gives you the following chances to create a stack overflow, 
or a mysterious memory crash:
	- allocating a too small array, 
	  passing the array to OpenGL, which needs a bigger array !

	  This semantics are not checked.
	  I have just tried to create this kind of crash,
	  but I was not succesfull :-(
	  Demo "select.java":
		I gave the "vp"-array just a zero size.
		"vp" is passed to GL and GLU !
		But it works ... may be because the JVM allocates enough
		memory, so we did not crossed the border to an illegal
		memory area .. ?!

	I suppose, that - if somebody has the time - 
	to add semantic arrays checks for another debug-test library !
	But this task would be _very_ time consuming,
	because the many functions we do have.

This "user" mistake, or a bug within the GL driver (which one are you using 
?), can create those mysterical results !

Try to make JVM's startup and average memory heaps bigger !
If no error will occure, I really would guess, it is about a wrong arrays 
size.

Comments and Ideas about automatically array-size checking 
for Java<->JNI are welcome.
 
> BTW, remember my posts from about two weeks ago? I believe it was one of
> such situations.
>

I must check my email archive.

> I'm using GNU/Linux RedHat 7.0, GL4Java 2.4.0.0 and Sun JDK 1.3.
>
Which OpenGL driver ?

Mesa 3.X ?
XFree86 4.0.X - DRI / XXX ?
NVidia ?

> Bye,
> Max
>

It would be cool, to have a very array consuming Java/OpenGL
example, which always tries to run out of any bounds,
even the JVM pre-allocated memory bounds.

Kind regards, Sven

> --
> -----------------------------------------------
> Max Gilead                     gi...@li...
> XMage library      http://xmage.sourceforge.net
> -----------------------------------------------
> -- Sex on TV is bad. You might fall off...

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