If a member is an empty class, the standard normally stats that it needs
to have a size of at least 1 byte in order to guarantee that the
addresses of distinct objects of the same type are always distinct.
However as of c++20, we can use [[no_unique_address]] to instruct the
compiler that if the member has an empty type, it may optimize it to
occupy no space.
The insert_before method on AK::InlineLinkedList is used, so in order to
achieve feature parity, we need to implement it for AK::IntrusiveList as
well.
In order for IntrusiveList to be capable of replacing InlineLinkedList,
it needs to support reverse iteration. InlineLinkedList currently
supports manual reverse iteration by calling list->last() followed by
node->prev().
Problem:
- The constructor is defined to be the default constructor.
Solution:
- Let the compiler generate the destructor by setting it to the
default.
Removing the element from the intrusive linked list might not be safe
if doing so requires a lock. Instead this is something the caller
should have done so let's verify instead that we're not on any lists.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
PR #6376 made IntrusiveList capable of holding RefPtr<T>, etc. however
there was a latent bug where take_first() / take_last() would fail to
compile because they weren't being converted to their container type.
This should allow creating intrusive lists that have smart pointers,
while remaining free (compared to the impl before this commit) when
holding raw pointers :^)
As a sidenote, this also adds a `RawPtr<T>` type, which is just
equivalent to `T*`.
Note that this does not actually use such functionality, but is only
expected to pave the way for #6369, to replace NonnullRefPtrVector<T>
with intrusive lists.
As it is with zero-cost things, this makes the interface a bit less nice
by requiring the type name of what an `IntrusiveListNode` holds (and
optionally its container, if not RawPtr), and also requiring the type of
the container (normally `RawPtr`) on the `IntrusiveList` instance.
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
And use it in the scheduler.
IntrusiveList is similar to InlineLinkedList, except that rather than
making assertions about the type (and requiring inheritance), it
provides an IntrusiveListNode type that can be used to put an instance
into many different lists at once.
As a proof of concept, port the scheduler over to use it. The only
downside here is that the "list" global needs to know the position of
the IntrusiveListNode member, so we have to position things a little
awkwardly to make that happen. We also move the runnable lists to
Thread, to avoid having to publicize the node.
