Access Violation in glMultiDrawElements ?

OpenGL OpenGL: Basic Coding
1

Hey guys!
While reading the ‘red book’,the code “mvarray.c”

 
   static GLint vertices[] = {25, 25,
                       75, 75,
                       100, 125,
                       150, 75,
                       200, 175,
                       250, 150,
                       300, 125,
                       100, 200,
                       150, 250,
                       200, 225,
                       250, 300,
                       300, 250};

   glEnableClientState (GL_VERTEX_ARRAY);
   glVertexPointer (2, GL_INT, 0, vertices);
   static GLubyte oneIndices[] = {0, 1, 2, 3, 4, 5, 6};
   static GLubyte twoIndices[] = {1, 7, 8, 9, 10, 11};
   static GLsizei count[] = {7, 6};
   static GLvoid * indices[2] = {oneIndices, twoIndices};
   
   glClear (GL_COLOR_BUFFER_BIT);
   glColor3f (1.0, 1.0, 1.0);
   glMultiDrawElements (GL_LINE_STRIP, count, GL_UNSIGNED_BYTE,
                           indices, 2);   glFlush ();

there is an Access Violation in glMultiDrawElements.
while debuging it shows "unhandled exception in mvarray.exe : 0xc0000005 :Access Violation ".
but when its equal form:


        int i;
	for (i = 0;i < 2;i++)
	{
		if (count[i] > 0)
		{
			glDrawElements(GL_LINE_STRIP,count[i],GL_UNSIGNED_BYTE,indices[i]);
		}
	}

it works just fine.
I use VC6 under WinXP.
so pls tell me why?
thx!

2

I suspect something is wrong with your pointer to the count array, or the pointer to pointers array. I tend to use actual pointers, or reference arrays as &array[0] in GL calls.

Perhaps see if that solves it.

The crash you are getting certainly seems like one where GL is accessing somewhere it shouldn’t with an invalid pointer…

3

Problem solved!