extensions in 4.3.x

I've got an extension which was written for 4.1/4.2, and everything worked great. I've just (by accident of me not paying attention to an apt-get dist-upgrade) upgraded to 4.3.2 and I can't get the extension to compile now. I keep getting bitching about unresolved symbols. Does anybody have any docs kicking around as to how the build process changed between 4.2.x and 4.3.x so that I can fix this extension up please? Also, as an interesting sidenote... The .so file that was compiled under 4.2.2 is fully useable under 4.3.2 as well for some reason. Not quite sure why though, I'd have assumed it'd need to be recompiled. Cheers, -- Gareth Ardron