Segmentation fault with glBufferData()

Question

I can't work out why this code is seg faulting:

AxesMarker::AxesMarker(float size)
    : size_(size), vbo_vertices_(0), vbo_elements_(0)
{
  Vertex vertices[6] = { 
      Vertex(Color4f::RED, Vector3f::ZERO, Vector3f::ZERO),
      Vertex(Color4f::RED, Vector3f::ZERO, Vector3f(size_, 0.0f, 0.0f)),
      Vertex(Color4f::BLUE, Vector3f::ZERO, Vector3f::ZERO),
      Vertex(Color4f::BLUE, Vector3f::ZERO, Vector3f(0.0f, size_, 0.0f)),
      Vertex(Color4f::GREEN, Vector3f::ZERO, Vector3f::ZERO),
      Vertex(Color4f::GREEN, Vector3f::ZERO, Vector3f(0.0f, size_, 0.0f)) };

  GLuint elements[6] = { 0, 1, 2, 3, 4, 5 };

  fprintf(stderr, "sizeof(vertices): %d, sizeof(Vertex): %d", (int) sizeof(vertices), (int) sizeof(Vertex));

  /* create buffers */
  glGenBuffers(1, &vbo_vertices_);
  glGenBuffers(1, &vbo_elements_);

  /* bind buffers */
  glBindBuffer(GL_ARRAY_BUFFER, vbo_vertices_);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vbo_elements_);

  /* buffer data */
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

  /* unbind buffers */
  glBindBuffer(GL_ARRAY_BUFFER, 0); 
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0); 
}

Compiles with no warnings, but appears to be seg faulting on the first call to glBufferData(). I can post more code if necessary, I'm not familiar enough with GL to know what might be relevant. Thanks!

  GLfloat vertices[60] = { 
     1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
     1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
     0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
     0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f,
     0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
     0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f };

yields same seg fault.

Darcy Rayner · Accepted Answer · 2011-08-14T04:58:47.123

5

Is your Vertex class a plain old data type? Does it have any virtual functions which might mean it also has a vtable? Can you try re-writing this code using an array of plain floats,(just to test your calls to glBufferData are working). From what I can tell though, it looks like you are using glBufferData correctly, but then again I might have missed something.

EDIT: Did you make absolutely sure that your OpenGL context is fully initialised before you call this code. Is this a global object, because it's constructor might be called before main?

edited Aug 14 '11 at 04:58

answered Aug 14 '11 at 03:47

Darcy Rayner

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They're all structs I will try that though. – Rhys van der Waerden Aug 14 '11 at 03:50
Ahh, so this is for real time then. I better stop trying so hard to help then. :) – Darcy Rayner Aug 14 '11 at 03:57
1

Are you using Glew? Did you remember to call glewInit before making the openGL calls? – Darcy Rayner Aug 14 '11 at 04:05
I had not done that, but it didn't change anything... I just don't understand why glBufferData is reading past the end of the array. – Rhys van der Waerden Aug 14 '11 at 04:10
As I said before, I can't see anything wrong with how you are calling the code. Did you make absolutely sure that your OpenGL context is fully initialised before you call this code. Is this a global object, because it's constructor might be called before main? – Darcy Rayner Aug 14 '11 at 04:19
That was the problem, thanks. (update your answer so I can tick you) – Rhys van der Waerden Aug 14 '11 at 04:46

Segmentation fault with glBufferData()

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