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Asked: 2026-05-15T16:39:43+00:00

I’m writing an iPhone application which uses UIView with a CAEAGLayer as its layer.

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I’m writing an iPhone application which uses UIView with a CAEAGLayer as its layer. Everything is fine and working apart from 1 small problem: sometimes it crashes with EXC_BAD_ACCESS and the following stack trace:

    [EAGLView draw]
    glDrawArrays_Exec
    PrepareToDraw
    DrawFramebufferMakeResident
    AttachmentMakeResident
    TextureMakeResident
    memmove

it crashes on the line:

    glVertexPointer(3, GL_FLOAT, 0, vertexCoordinates);
    glTexCoordPointer(2, GL_FLOAT, 0, textureCoordinates);
    glBindTexture(GL_TEXTURE_2D, textures[kActiveSideLeft]);
    glDrawArrays(GL_TRIANGLE_STRIP, 0, totalPoints); //<--Crash here

Application will only crash during interface rotation change (that also happens to be the only case when the view frame changes). It doesn’t crash often; most of the time it takes 3-5 minutes of rotating device to reproduce this problem.
I believe I’m making a mistake which is related to CAEAGLLayer initialization / frame change since that’s where it crashes (I believe).
So here are the init and layout subviews methods:
Init:

    ...
    CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer;     
    eaglLayer.opaque = TRUE;

    context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
    if (!context || ![EAGLContext setCurrentContext:context])
    {
        [self release];
        return nil;
    }

    glGenFramebuffersOES(1, &defaultFramebuffer);
    glGenRenderbuffersOES(1, &colorRenderbuffer);
    glGenRenderbuffersOES(1, &depthRenderbuffer);
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, defaultFramebuffer);
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, colorRenderbuffer);
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthRenderbuffer);
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, colorRenderbuffer);
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthRenderbuffer);
    ...

On set frame I only set GL_MODELVIEW and GL_POJECTION matrixes, so I guess nothing bad can happen there.
LayoutSubviews:

    - (void)layoutSubviews
    {
      [EAGLContext setCurrentContext:context];

        glBindRenderbufferOES(GL_RENDERBUFFER_OES, colorRenderbuffer);
        [context renderbufferStorage:GL_RENDERBUFFER_OES fromDrawable:(CAEAGLLayer*)self.layer];
        glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
        glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);
        glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthRenderbuffer);
        glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH_COMPONENT16_OES, backingWidth, backingHeight);

        NSAssert1(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) == GL_FRAMEBUFFER_COMPLETE_OES, @"Failed to make complete framebuffer object: %X", glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES));
    }

Draw method itself looks like:

        if ([EAGLContext currentContext] != context) {
            [EAGLContext setCurrentContext:context];
        }

        glBindFramebufferOES(GL_FRAMEBUFFER_OES, defaultFramebuffer);
        glViewport(0, 0, backingWidth, backingHeight);

        ...//drawing different triangle strips here

        glBindRenderbufferOES(GL_RENDERBUFFER_OES, colorRenderbuffer);
        [context presentRenderbuffer:GL_RENDERBUFFER_OES];

I’d appreciate any comments on the listed code or suggestions about how can I find out the cause of this bug.

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1 Answer

  1. Editorial Team

    I’d be suspicious of the totalPoints variable being passed to drawArrays, or maybe your values for vertexCorrdinates or textureCoordinates, if those arrays aren’t static. Your crash implies that you’re walking off the end of memory while drawing the arrays. I’m less suspicious of your GL setup and more concerned about your memory management, and what you’re drawing that’s different during the rotation.

    (Also, FWIW, I don’t think you should be calling RenderBufferStorage every time you bind the render buffer(s). You should only need to do that once when you create them. That said, I’m not sure that you shouldn’t actually destroy the buffers when you change their size and just recreate them from scratch.)

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