This caused the m_allocation_enabled_previously member to be technically
uninitialized when the compiler emits the implicit destructor call for
stack allocated classes.
This was pointed out by gcc on lagom builds, no clue how this was flying
under the radar for so long and is not triggering CI.
Except for tangential accessors such as data(), there is no more feature
of FixedArray that is untested after this large expansion of its test
cases. These tests, with the help of the new NoAllocationGuard, also
test the allocation contract that was fixated in the last commit.
Hopefully this builds confidence in future Kernel uses of FixedArray
as well as its establishment in the real-time parts of the audio
subsystem. I'm excited :^)
FixedArray always *almost* had the following allocation guarantees:
There is (possibly) one allocation in the constructor and one (or more)
deallocation(s) in the destructor. No other operation allocates or
deallocates. With this removal of the public clear() method, which
nobody except the test used anyways, those guarantees are now completely
true and furthermore fixated with an explanatory comment.
FixedArray now doesn't expose any infallible constructors anymore.
Rather, it exposes fallible methods. Therefore, it can be used for
OOM-safe code.
This commit also converts the rest of the system to use the new API.
However, as an example, VMObject can't take advantage of this yet,
as we would have to endow VMObject with a fallible static
construction method, which would require a very fundamental change
to VMObject's whole inheritance hierarchy.
Let's bring this class back, but without the confusing resize() API.
A FixedArray<T> is simply a fixed-size array of T.
The size is provided at run-time, unlike Array<T> where the size is
provided at compile-time.
