Function pointer arguments given to the guest thunk library aren't
callable on the host, so they need special handling on a case-by-case
basis. Similar problems arise when the guest-side tries to consume a
pointer returned from a native host library. To automate some common
scenarios, this change adds two new annotations:
"callback_guest" indicates the callback parameter is never called on the
host and hence can be marshalled like any other argument. Accidental host
calls to the function pointer are prevented by wrapping it in an opaque
type alias.
"returns_guest_pointer" indicates that the host function returns a pointer
usable in the guest context. This applies e.g. to functions that derive
the returned pointer from input guest pointer arguments.
Previously, the host thunk would seemingly succeed to load even when
the corresponding host library could not be loaded, leading to obscure
crashes later throughout execution.
Keeping this in the commit history to go back to later.
While these are required for static-pie builds to work, with the glibc
bug we can't use those yet.
Disable for now since it is is unnecessary.
Tony Wasserka