CL-GTK2 requires features from Common Lisp implementations that are beyound ANSI standard. Namely:

• FFI with callbacks (via CFFI)
• Threading (via Bordeaux-Threads)
• Weak references (weak hash-tables) and finalizers (via Trivial-Garbage)
• CLOS Metaobject Protocol (via Closer-MOP)

Exact version requirements are written in the Installation page.

CL-GTK2 was tested on following combinations of operating systems and lisp implementations:

• SBCL-1.0.28 on Gentoo Linux x86-64
• SBCL-1.0.18 on Ubuntu Linux x86
• SBCL-1.0.29 on Microsoft Windows XP x86
• Clozure CL-1.4 on Gentoo Linux x86-64
• Clozure CL-1.4 on Microsoft Windows XP x86

CL-GTK2 at this time works on Linux and Windows, on SBCL and Clozure CL (starting from version 1.4 of Clozure CL). It should be quite easily portable to other operating systems.