Posssible memory leak in OpenGL Intel Win7 drivers

Graphics and GPU Programming Programming OpenGL

Started by mshafey February 14, 2012 04:53 PM

35 comments, last by mshafey 12 years, 2 months ago

1,436

February 14, 2012 11:22 PM

What I described should work using Visual C++ and g++ as well. I don't know about the embedded systems, so thanks for clarifying.

Not for me...

c:\test>cat a.cpp

#include <stdio.h>

int main()

{

  int* ptr;

  printf("%p\n", ptr);

}

c:\test>g++ a.cpp



c:\test>a.exe

7EFDE000



c:\test>cl a.cpp /nologo

a.cpp

c:\test\a.cpp(5) : warning C4700: uninitialized local variable 'ptr' used



c:\test>a.exe

00000001



c:\test>

Yours3!f

1,534

February 14, 2012 11:30 PM

[quote name='Yours3!f' timestamp='1329260792' post='4913164']
What I described should work using Visual C++ and g++ as well. I don't know about the embedded systems, so thanks for clarifying.

It works on neither Visual C++ nor g++. Or, rather, it works for the very same reason that your unmapped buffer appeared valid; undefined behavior. Try, for example, to enable optimization and see that happens.
[/quote]

I use kdevelop which uses cmake and by default sets optimization to -O3, I tried in both debug and release mode, both works. Again it shouldn't.

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https://github.com/Yours3lf/instanced_font_rendering

http://youtu.be/k8PYkihyGXA

https://github.com/scrawl/smaa-opengl

https://github.com/Yours3lf/gl_browser_gui

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Yours3!f

1,534

February 14, 2012 11:32 PM

try this:

#include <stdio.h>
int* ptr;
int main()
{
printf("%p\n", ptr);
}[/quote]

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Stuff I wrote:

https://github.com/Yours3lf/libmymath

https://github.com/Yours3lf/linux_gl_fps

https://github.com/Yours3lf/instanced_font_rendering

http://youtu.be/k8PYkihyGXA

https://github.com/scrawl/smaa-opengl

https://github.com/Yours3lf/gl_browser_gui

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Brother Bob

10,350

February 14, 2012 11:39 PM

try this:

Primitives at global scope are always default initialized to zero. At function scope, they are not.

Yours3!f

1,534

February 14, 2012 11:46 PM

[quote name='Yours3!f' timestamp='1329262329' post='4913178']
try this:

Primitives at global scope are always default initialized to zero. At function scope, they are not.
[/quote]

I know, that's why replied it. but lets return to the topic now. solving the memory leak...

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Stuff I wrote:

https://github.com/Yours3lf/libmymath

https://github.com/Yours3lf/linux_gl_fps

https://github.com/Yours3lf/instanced_font_rendering

http://youtu.be/k8PYkihyGXA

https://github.com/scrawl/smaa-opengl

https://github.com/Yours3lf/gl_browser_gui

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21st Century Moose

13,459

February 14, 2012 11:48 PM

int *ptr, MSVC 2008, debug build, value of 0x0018f668.

Just because it works on one person's machine using a specific compiler does not make it globally valid. The C/C++ standard is quite explicit that uniitalized pointers are undefined. That means that the compiler is largely free to do whatever it wants with them; it may give a value of 0, it may set to random garbage, and that random garbage may or may not point to somewhere valid in memory.

If you're in the habit of doing this, and of relying on it, please remind me to never use any software you write.

Direct3D has need of instancing, but we do not. We have plenty of glVertexAttrib calls.

Yours3!f

1,534

February 15, 2012 12:01 AM

If you're in the habit of doing this, and of relying on it, please remind me to never use any software you write.

I always clean up any warning the compiler gives, and this includes uninitialized variables. So that kind of thing isn't going to happen ever in software I write.

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Stuff I wrote:

https://github.com/Yours3lf/libmymath

https://github.com/Yours3lf/linux_gl_fps

https://github.com/Yours3lf/instanced_font_rendering

http://youtu.be/k8PYkihyGXA

https://github.com/scrawl/smaa-opengl

https://github.com/Yours3lf/gl_browser_gui

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bubu LV

1,436

February 15, 2012 01:20 AM

But you define all your pointer variables global, not local?

Yours3!f

1,534

February 15, 2012 01:44 AM

But you define all your pointer variables global, not local?

why did you think that? I just wanted to show you a case where an uninitialized pointer actually is initialized. That was all.
I didn't imply that I use only global variables...

Blog:

http://extremeistan.wordpress.com/

Stuff I wrote:

https://github.com/Yours3lf/libmymath

https://github.com/Yours3lf/linux_gl_fps

https://github.com/Yours3lf/instanced_font_rendering

http://youtu.be/k8PYkihyGXA

https://github.com/scrawl/smaa-opengl

https://github.com/Yours3lf/gl_browser_gui

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Yours3!f