Quote Originally Posted by michalis

It's not related to Linux or Windows. Insted, it's graphic-card specific. On some graphic cards you may even always get alpha buffer, even when you didn't request it. Or always get stencil buffer (although this is rare). And so on. The settings you give in SDL_GL_SetAttribute are a minumum requirements --- so if your desktop is already 32bpp, it's no wonder that resulting context also has 32bpp, even though you didn't request so much.
So, actually the calls to SDL_GL_SetAttribute may be omited (except setting the alpha and stencil buffer) since it is up to graphics card what I will get?