Previously, in LibGFX's `Point` class, calculated distances were passed
to the integer `abs` function, even if the stored type was a float. This
caused the value to unexpectedly be truncated. Luckily, this API was not
used with floating point types, but that can change in the future, so
why not fix it now :^)
Since we are in C++, we can use function overloading to make things
easy, and to automatically use the right version.
This is even better than the LibC/LibM functions, as using a bit of
hackery, they are able to be constant-evaluated. They use compiler
intrinsics, so they do not depend on external code and the compiler can
emit the most optimized code by default.
Since we aren't using the C++ standard library's trick of importing
everything into the `AK` namespace, this `abs` function cannot be
exported to the global namespace, as the names would clash.
These were an ad-hoc way to implement special behaviour when reading or
writing to specific object properties. Because these were effectively
replaced by the abillity to override the internal methods of Object,
they are no longer needed.
It's way too easy to get this wrong: for the IsArray abstract operation,
Value::is_array() needs to be called. Since we have RTTI, the virtual
Object::is_array() method is not needed anymore - if we need to know
whether something is *actually* a JS::Array (we currently check in more
cases than we should, I think) and not a Proxy with an Array target, we
should do that in a way that doesn't look like an abstract operation.
This is a huge patch, I know. In hindsight this perhaps could've been
done slightly more incremental, but I started and then fixed everything
until it worked, and here we are. I tried splitting of some completely
unrelated changes into separate commits, however. Anyway.
This is a rewrite of most of Object, and by extension large parts of
Array, Proxy, Reflect, String, TypedArray, and some other things.
What we already had worked fine for about 90% of things, but getting the
last 10% right proved to be increasingly difficult with the current code
that sort of grew organically and is only very loosely based on the
spec - this became especially obvious when we started fixing a large
number of test262 failures.
Key changes include:
- 1:1 matching function names and parameters of all object-related
functions, to avoid ambiguity. Previously we had things like put(),
which the spec doesn't have - as a result it wasn't always clear which
need to be used.
- Better separation between object abstract operations and internal
methods - the former are always the same, the latter can be overridden
(and are therefore virtual). The internal methods (i.e. [[Foo]] in the
spec) are now prefixed with 'internal_' for clarity - again, it was
previously not always clear which AO a certain method represents,
get() could've been both Get and [[Get]] (I don't know which one it
was closer to right now).
Note that some of the old names have been kept until all code relying
on them is updated, but they are now simple wrappers around the
closest matching standard abstract operation.
- Simplifications of the storage layer: functions that write values to
storage are now prefixed with 'storage_' to make their purpose clear,
and as they are not part of the spec they should not contain any steps
specified by it. Much functionality is now covered by the layers above
it and was removed (e.g. handling of accessors, attribute checks).
- PropertyAttributes has been greatly simplified, and is being replaced
by PropertyDescriptor - a concept similar to the current
implementation, but more aligned with the actual spec. See the commit
message of the previous commit where it was introduced for details.
- As a bonus, and since I had to look at the spec a whole lot anyway, I
introduced more inline comments with the exact steps from the spec -
this makes it super easy to verify correctness.
- East-const all the things.
As a result of all of this, things are much more correct but a bit
slower now. Retaining speed wasn't a consideration at all, I have done
no profiling of the new code - there might be low hanging fruits, which
we can then harvest separately.
Special thanks to Idan for helping me with this by tracking down bugs,
updating everything outside of LibJS to work with these changes (LibWeb,
Spreadsheet, HackStudio), as well as providing countless patches to fix
regressions I introduced - there still are very few (we got it down to
5), but we also get many new passing test262 tests in return. :^)
Co-authored-by: Idan Horowitz <idan.horowitz@gmail.com>
This is not exactly compliant with the specification, but our current
bound function implementation isn't either, so its not currently
possible to implement it the way the specification requires.
The unsigned shift right implementation was already doing this, but
the spec requires a mod32 of rhs before the shift for the signed shift
right implementation as well. Caught by UBSAN and oss-fuzz.
If the value we get after fmod in Value::to_u32 is negative, UBSAN
complains that -N is out of bounds for u32. An extra static cast to i64
makes it stop complaining. An alternative implementation could add 2^32
if the fmod'd value is negative. Caught by UBSAN and oss-fuzz.
This was a standalone function previously (get_method()), but instead of
passing a Value to it, we can just make it a method.
Also add spec step comments and fix the receiver value by using GetV().
Like Get(), but with any value instead of an object - it's calling
ToObject() for us and passes the value to [[Get]]() as the receiver.
This will be used in GetMethod() (and a couple of other places, which
can be updated over time).
I also tried something new here: adding the three steps from the spec as
inline comments :^)
Requires a bunch of find-and-replace updates across LibJS, but
constructing a PropertyName from a nullptr Symbol* should not be
possible - let's enforce this at the compiler level instead of using
VERIFY() (and already dereference Symbol pointers at the call site).
Value.{cpp,h} has become a dumping ground, let's change that.
Things that are directly related to Values (e.g. bitwise/binary ops,
equality related functions) can remain, but everything else that's not a
Value or Object method and globally required (not just a static function
somewhere) is being moved.
Also convert to east-const while we're here.
I haven't touched IteratorOperations.{cpp,h}, it seems fine to still
have those separately.
As mentioned on Discord earlier, we'll add these to all new functions
going forward - this is the backfill. Reasons:
- It makes you look at the spec, implementing based on MDN or V8
behavior is a no-go
- It makes finding the various functions that are non-compliant easier,
in the future everything should either have such a comment or, if it's
not from the spec at all, a comment explaining why that is the case
- It makes it easier to check whether a certain abstract operation is
implemented in LibJS, not all of them use the same name as the spec.
E.g. RejectPromise() is Promise::reject()
- It makes it easier to reason about vm.arguments(), e.g. when the
function has a rest parameter
- It makes it easier to see whether a certain function is from a
proposal or Annex B
Also:
- Add arguments to all functions and abstract operations that already
had a comment
- Fix some outdated section numbers
- Replace some ecma-international.org URLs with tc39.es
The second argument (the default constructor) and the return value have
to be constructors (as a result functions), so we can require that
explicitly by using appropriate types.
We already have two separate implementations of this, so let's do it
properly. The optional value type check is done by a callback function
that returns Result<void, ErrorType> - value type accepted or message
for TypeError, that is.
This was missing from Value::is_array(), which is equivalent to the
spec's IsArray() abstract operation - it treats a Proxy value with an
Array target object as being an Array.
It can throw, so needs both the global object and an exception check
now.
Throws an exception if the given value is nullish, returns it otherwise.
We can now gradually replace such manual checks with this function where
applicable.
This also has the advantage that the somewhat useless "ToObject on null
or undefined" will be replaced with "null cannot be converted to an
object" or "undefined cannot be converted to an object". :^)
Problem:
- `static` variables consume memory and sometimes are less
optimizable.
- `static const` variables can be `constexpr`, usually.
- `static` function-local variables require an initialization check
every time the function is run.
Solution:
- If a global `static` variable is only used in a single function then
move it into the function and make it non-`static` and `constexpr`.
- Make all global `static` variables `constexpr` instead of `const`.
- Change function-local `static const[expr]` variables to be just
`constexpr`.
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 *
We should be able to get the 'typeof' string for any value directly, so
this is now a standalone Value::typeof() method instead of being part of
UnaryExpression::execute().
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
This commit replaces the usage of String::starts_with with
Utf8View::starts_with, which first decodes the utf8 encoded
string, and as such can take things like overlong encoded
sequences into account (which could otherwise cause the prefix
check to be inconsistent with the following code points check).
Just like to_size_t() - which was already removed in f369229 - this is
non-standard, use to_length() instead. One remaining use was removed,
and I'm glad it's gone. :^)
We now store 32-bit integers as 32-bit integers directly which avoids
having to convert them from doubles when they're only used as 32-bit
integers anyway. :^)
This patch feels a bit incomplete and there's a lot of opportunities
to take advantage of this information. We'll have to find and exploit
them eventually.
