gdkcursor-quartz.c uses the instancetype keyword, which doesn't seem to be supported in the version of Objective C that Snow Leopard uses. Replacing that keyword with the thing it represents makes it build.
Patch by Ryan Hendrickson, http://bugzilla.gnome.org/show_bug.cgi?id=756770
64c5b97 quartz: Don't use the instancetype keyword
gdk/quartz/gdkcursor-quartz.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)