[vm/ffi] Pointer<Null>

[dcharkes]

What do we do with Pointer<Null> in the FFI? (This is allowed by the Dart language.)

[sjindel-google]

This type could be useful for the nullptr constant, so that we don't need to cast it to use it in other contexts:

Pointer<Null> nullptr = Pointer<Null>.fromAddress(0);

// ...
void takesPtr(Pointer<Int8> ptr);
// ...

takesPtr(nullptr);  // Actually works!

[dcharkes]

linking #35756

[sjindel-google]

What needs to happen? AFAICT, everything is working as intended.

[dcharkes]

We don't actually use Pointer<Null> as nullptr:

/// Represents a pointer into the native C memory.
final Pointer<Void> nullptr = Pointer.fromAddress(0);

If we can, we should change it to that maybe.

We don't have any tests containing Pointer<Null>, we should probably add one.