c,opengl , OpenGL glTexImage2D memory issue


OpenGL glTexImage2D memory issue

Question:

Tag: c,opengl

I'm loading a cubemap to create a skybox, everything is fine and the skybox renders properly with a correct texture application.

However, I decided to check my program safety with valgrind, Valgrind gives this error: http://pastebin.com/seqmXjyx

The line 53 in sky.c is:

glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, texture.width, texture.height, 0, GL_BGR, GL_UNSIGNED_BYTE, texture.pixels);

protoype:
void glTexImage2D( GLenum target,
              GLint level,
              GLint internalformat,
              GLsizei width,
              GLsizei height,
              GLint border,
              GLenum format,
              GLenum type,
              const GLvoid *pixels )

The texture width and height are unsigned int (1024x1024), and the pixels have bmp texture format.

It is correctly parsed for sure (as I said before, everything is rendered correctly, openGL returns no error, I only get this invalid write of 4 from valgrind).

(this invalid write appear every time I load a texture)

So I read the man, and it made me even more confused, this is what I get from it:

GL_INVALID_VALUE is generated if width or height is less than 0 or greater than 2 + GL_MAX_TEXTURE_SIZE, or if either cannot be represented as 2^k +2 (border) for some integer value of k.

glGetError() gives me GL_NO_ERROR, when I'm sending 1024*1024 as parameters, which is obviously not (2^k + 2)

I also read about the border parameter, which seems kind of useless for now the openGL I use, but could this be link to this overwrite?

Finally, as I said, everything works properly, but I would definitely like to know where are these invalids writes coming from.

The full project: https://github.com/toss-dev/minetoss


Answer:

Which man page are you quoting? There are multiple man pages available, not all mapping to the same OpenGL version.

Anyways, the idea behind the + 2 (border) is to have 2 multiplied by the value of border, which is in your case 0. So your code is just fine. border is a feature that is not supported by the latest GL versions and is therefore absent from the more recent man pages.

Now, back to your problem. The valgrind error is coming from within the GeForce GL driver, so unless you get access to the source, it's unlikely you'll get anywhere investigating it (you can try to contact the driver maintainers if you want... but may have a hard time getting any answer).


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