GL library compilation question OS X

Does anyone know how to get the GL library head开发者_开发技巧ers for OS X 10.6 (Snow Leopard)? E.g. I'm getting this error with a sudo port install:

configure: error: You don't seem to have the GL library headers installed.

TIA, Craig

If you installed the developer tools from the OSX install DVD (xcode, etc), they should have already been installed. If you didn't, you can download a disk image from apple's site of the developer tools installer, then mount it and run the installer to get the GL headers.