[Merged by Bors] - Make JsString conform to miri tests
#2412
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jedel1043
requested review from
Razican,
jasonwilliams,
HalidOdat,
RageKnify and
raskad
Test262 conformance changes
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Codecov Report
@@ Coverage Diff @@
## main #2412 +/- ##
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Coverage 38.41% 38.42%
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Files 313 313
Lines 23974 23982 +8
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+ Hits 9210 9214 +4
- Misses 14764 14768 +4
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Razican
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Nov 6, 2022
raskad
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Nov 6, 2022
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Nov 6, 2022
This PR rewrites some patterns of the `JsString` implementation in order to pass all its miri tests. This can be verified by running: ```bash cargo +nightly miri test -p boa_engine string::tests -- --skip builtins --skip parser ``` Basically, we were doing two operations that were Undefined Behaviour per the [Stacked Borrows](https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md) model: - Casting `&JsString` to `&mut RawJsString` to `&[u16]`. The intermediate mutable borrow must not exist, or Miri considers this as Undefined Behaviour. - Trying to access `RawJsString.data` using the dot operator. Miri complains with `this is a zero-size retag ([0x10..0x10]) so the tag in question does not exist anywhere`. To fix this, we can recompute the position of `data` every time we want to access it.
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Pull request successfully merged into main. Build succeeded: |
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JsString conform to miri testsJsString conform to miri tests
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This PR rewrites some patterns of the
JsStringimplementation in order to pass all its miri tests. This can be verified by running:cargo +nightly miri test -p boa_engine string::tests -- --skip builtins --skip parserBasically, we were doing two operations that were Undefined Behaviour per the Stacked Borrows model:
&JsStringto&mut RawJsStringto&[u16]. The intermediate mutable borrow must not exist, or Miri considers this as Undefined Behaviour.RawJsString.datausing the dot operator. Miri complains withthis is a zero-size retag ([0x10..0x10]) so the tag in question does not exist anywhere. To fix this, we can recompute the position ofdataevery time we want to access it.