This patch adds two macros to declare per-type allocators:
- JS_DECLARE_ALLOCATOR(TypeName)
- JS_DEFINE_ALLOCATOR(TypeName)
When used, they add a type-specific CellAllocator that the Heap will
delegate allocation requests to.
The result of this is that GC objects of the same type always end up
within the same HeapBlock, drastically reducing the ability to perform
type confusion attacks.
It also improves HeapBlock utilization, since each block now has cells
sized exactly to the type used within that block. (Previously we only
had a handful of block sizes available, and most GC allocations ended
up with a large amount of slack in their tails.)
There is a small performance hit from this, but I'm sure we can make
up for it elsewhere.
Note that the old size-based allocators still exist, and we fall back
to them for any type that doesn't have its own CellAllocator.
Previously these handlers duplicated code and used formats that
were different from the one Error.prototype.stack uses.
Now they use the same Error::stack_string function, which accepts
a new parameter for compacting stack traces with repeating frames.
This loosens the connection to the AST interpreter and will allow us to
generate SourceRanges for the Bytecode interpreter in the future as well
Moves UnrealizedSourceRanges from TracebackFrame to the JS namespace for
this
Instead of eagerly populating the stack trace with a textual
representation of every call frame, just store the raw source code range
(code, start offset, end offset). From that, we can generate the full
rich backtrace when requested, and save ourselves the trouble otherwise.
This makes test-wasm take ~7 seconds on my machine instead of ~60. :^)
This includes an Error::create overload to create an Error from a UTF-8
StringView. If creating a String from that view fails, the factory will
return an OOM InternalError instead. VM::throw_completion can also make
use of this overload via its perfect forwarding.
DeprecatedFlyString relies heavily on DeprecatedString's StringImpl, so
let's rename it to A) match the name of DeprecatedString, B) write a new
FlyString class that is tied to String.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
This is a continuation of the previous two commits.
As allocating a JS cell already primarily involves a realm instead of a
global object, and we'll need to pass one to the allocate() function
itself eventually (it's bridged via the global object right now), the
create() functions need to receive a realm as well.
The plan is for this to be the highest-level function that actually
receives a realm and passes it around, AOs on an even higher level will
use the "current realm" concept via VM::current_realm() as that's what
the spec assumes; passing around realms (or global objects, for that
matter) on higher AO levels is pointless and unlike for allocating
individual objects, which may happen outside of regular JS execution, we
don't need control over the specific realm that is being used there.
The fact that they *are* subclasses is an implementation detail and
should not be highlighted. The spec calls these NativeErrors, so let's
use that.
Also added a comment explaining *why* they inherit from Error - I was
about to change that :^)
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 *
The previous handling of the name and message properties specifically
was breaking websites that created their own error types and relied on
the error prototype working correctly - not assuming an JS::Error this
object, that is.
The way it works now, and it is supposed to work, is:
- Error.prototype.name and Error.prototype.message just have initial
string values and are no longer getters/setters
- When constructing an error with a message, we create a regular
property on the newly created object, so a lookup of the message
property will either get it from the object directly or go though the
prototype chain
- Internal m_name/m_message properties are no longer needed and removed
This makes printing errors slightly more complicated, as we can no
longer rely on the (safe) internal properties, and cannot trust a
property lookup either - get_without_side_effects() is used to solve
this, it's not perfect but something we can revisit later.
I did some refactoring along the way, there was some really old stuff in
there - accessing vm.call_frame().arguments[0] is not something we (have
to) do anymore :^)
Fixes#6245.
