I have run into a problem using textures. I create several textures, do some drawing, delete the textures, then do it all over again. I am getting a segmentation fault the second time I create the textures, on the first call to glTexImage2D(). I have ascertained that the problem is related to the setting of a parameter.
In the function where I use the textures, after glBindTexture(), I do
glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
where width is the frame width. If width is greater than 521, I get a seg fault later when I try to recreate the textures.
I have a simple code example that manifests this problem, but I don’t know how to post it here.
What exactly are you trying to do? width in your example should be the width of the image you are giving to glTexImage2d. I have never used this feature, but I am assuming it would be used for a case like this.
Assume you have an image that is 300x300 and the portion of it from 0,0 to 255, 255 is the section you want to use as a texture. You would set the GL_UNPACK_ROW_ALIGNMENT to 300 so that when it would get data for the next row it would skip the data for 256-299.
I’m guessing the reason you are getting a seg fault is because your image data has no such padding, and therefore you are causing glTexImage2D to read past the end of your image array.
The point was that the texture creation works fine the first time, but the second time through the loop causes a seg fault. I have found the solution. It seems that this is one of the situations where it is necessary to save and restore the client attributes.
I have put glPushClientAttrib(GL_CLIENT_PIXEL_STORE_BIT) before the draw() call, and glPopClientAttrib() after it, and now the test program and my real program both work as intended.
The point was that the texture creation works fine the first time, but the second time through the loop causes a seg fault. I have found the solution. It seems that this is one of the situations where it is necessary to save and restore the client attributes.
I have put glPushClientAttrib(GL_CLIENT_PIXEL_STORE_BIT) before the draw() call, and glPopClientAttrib() after it, and now the test program and my real program both work as intended.