Hi all, I don't have a github.com account, so reporting here. Hope that's ok. I found these bugs after Cale posted a link to some problematic behaviour (which probably failed initially due to lack of an OpenGL context): http://lpaste.net/118704 The first bug is lack of error checking in createShader: ---8<--- createShader :: ShaderType -> IO Shader createShader = fmap Shader . glCreateShader . marshalShaderType ---8<--- http://hackage.haskell.org/package/OpenGL-2.10.0.0/docs/src/Graphics-Renderi... glCreateShader returns 0 on error, and using that "not a shader" id for other calls is bound to cause chaos. https://www.opengl.org/sdk/docs/man/html/glCreateShader.xhtml The second bug is much more serious, a lack of error checking in shaderVar: ---8<--- shaderVar :: (GLint -> a) -> GetShaderPName -> Shader -> GettableStateVar a shaderVar f p shader = makeGettableStateVar $ alloca $ \buf -> do glGetShaderiv (shaderID shader) (marshalGetShaderPName p) buf peek1 f buf ---8<--- http://hackage.haskell.org/package/OpenGL-2.10.0.0/docs/src/Graphics-Renderi... glGetShaderiv doesn't modifiy the contents of buf on error. This means uninitialized memory is read by peek1 and then presumably used by f, which can cause a crash (in the best case) or wrong/undefined behaviour (in the worst case). https://www.opengl.org/sdk/docs/man/html/glGetShader.xhtml Thanks for reading, Claude -- http://mathr.co.uk