The compiler-generated copy constructor and copy assignment operator
already do the right thing (which is to simply copy the underlying
pointer).
The [Itanium C++ ABI][1] treats any class with non-trivial copy/move
constructors and destructors as non-trivial for the purposes of calls --
even if they are functionally identical to the compiler-generated ones.
If a class is non-trivial, it cannot be passed or returned in registers,
only via an invisible reference, which is worse for codegen. This commit
makes `{Nonnull,}GCPtr` trivial.
As the compiler can be sure that capturing a `GCPtr` by value has no
side effects, a few `-Wunused-lambda-capture` warnings had to be
addressed in LibWeb.
GCC seems to have a bug that prevents `ExceptionOr<Variant<GCPtr<T>>>`
from being implicitly constructed from `GCPtr<T>` after this change. A
non-invasive workaround is to explicitly construct the inner Variant
type.
[1]: https://itanium-cxx-abi.github.io/cxx-abi/abi.html#non-trivial
There are quite a few steps between a ReadableStream being created and
its controller being set. If GC occurs between those points, we will
have an empty Optional in ReadableStream::visit_edges. Seen on YouTube.
This is not documented yet, but the preferred style is getting both
upfront instead of inlining various kinds of calls in places that use
the realm and vm.
Note that as of this commit, there aren't any such throwers, and the
call site in Heap::allocate will drop exceptions on the floor. This
commit only serves to change the declaration of the overrides, make sure
they return an empty value, and to propagate OOM errors frm their base
initialize invocations.
This needs to happen before prototype/constructor intitialization can be
made lazy. Otherwise, GC could run during the C++ constructor and try to
collect the object currently being created.
These classes only needed Window to get at its realm. Pass a realm
directly to construct Crypto, Encoding, HRT, IntersectionObserver,
NavigationTiming, Page, RequestIdleCallback, Selection, Streams, URL,
and XML classes.
