Bug: Ladybird crashes on launch on macOS 26.4+ with “UNEXPECTED ERROR:
close: Bad file descriptor” in SharedVersion.cpp — because
AnonymousBuffer creation fails.
Cause: anon_create() passed O_CLOEXEC in the oflag argument to shm_open.
macOS 26.4+ rejects that with EINVAL. POSIX only specifies O_RDONLY,
O_RDWR, O_CREAT, O_EXCL, and O_TRUNC as valid shm_open flags; on earlier
macOS versions, O_CLOEXEC just happened to also be silently accepted.
Fix: Filter O_CLOEXEC from the oflag argument we pass to shm_open flags,
and instead set FD_CLOEXEC via fcntl — after opening.
The mmap() call here served no purpose - anon_create() is only meant to
create and return a file descriptor. The actual mapping is done later
by AnonymousBufferImpl::create().
This leaked an mmap of `size` bytes for every AnonymousBuffer created,
which includes backing stores, shareable bitmaps, and more.
The system uses ssize_t so it can return -1 in case of an error. But in
our case, we will transform that to an AK::Error, thus we never return
-1. Let's return size_t instead.
This uses splice on Linux and mmap+write elsewhere to transfer a file to
a pipe. Note we cannot use sendfile because (at least on macOS) the
receiving fd must be a socket.
One benefit of using `poll` over `select` is that we can re-use the poll
structure list. But there's no guarantee that the underlying system will
reset the `revents` field back to 0. So let's explicitly do so.
This is a remnant from SerenityOS. Let's avoid confusion as to why we
negate errno when we call Error::from_syscall just to negate it again
when we store the error code.
