So let's simply say: The contents of the include part of extent are implictly wrapped into double quotes iff they don't start with '<' or '"', and no ".h" is appended. Easy rule, doesn't mix concepts, and is readable:

foreign import ccall "static !myproc myinclude.h" myProc :: ...

I agree: don't make the '.h' implicit. To me it looks much more readable when it's obvious which is the cid and which is the include. Cheers, Simon