lib: fix modulo sign in webidl convertToInt#62940
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lib: fix modulo sign in webidl convertToInt#62940deepview-autofix wants to merge 1 commit intonodejs:mainnodejs/node:mainfrom deepview-autofix:deepview/415d17df0cdeepview-autofix/node:deepview/415d17df0cCopy head branch name to clipboard
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ChALkeR
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #62940 +/- ##
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- Coverage 89.66% 89.63% -0.03%
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Files 706 706
Lines 219370 219424 +54
Branches 42065 42074 +9
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- Hits 196694 196681 -13
- Misses 14586 14633 +47
- Partials 8090 8110 +20
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Calculation at 64 bits is still off, will redo |
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I rewrote the whole thing and added more tests |
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Co-Authored-By: DeepView Autofix <276251120+deepview-autofix@users.noreply.github.com> Assisted-by: Claude <noreply@anthropic.com> Signed-off-by: Nikita Skovoroda <chalkerx@gmail.com>
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ExE-Boss
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| // 9. Set x to IntegerPart(x). | ||
| x = integerPart(x); | ||
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| // Following the exact algorithm looses precision on signed modulo in 64-bit |
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| // Following the exact algorithm looses precision on signed modulo in 64-bit | |
| // Following the exact algorithm loses precision on signed modulo in 64-bit |
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Closing in favor of #62979 |
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The modulo() helper in lib/internal/webidl.js is documented to implement ECMA-262's "x modulo y" (result has the same sign as y), but it used the JS % operator directly, whose result takes the sign of x. convertToInt step 10 relies on modulo(x, 2^bitLength) producing a non-negative representative in [0, 2^bitLength); step 11 only handles the signed upper half, so negative results of % were returned unchanged.
As a result, negative inputs to unsigned WebIDL integer types returned the original negative value instead of the two's-complement wrap (e.g. convertToInt('v', -3, 8) returned -3 instead of 253), and signed inputs in the one-wrap band below the lower bound were returned as-is (convertToInt('v', -200, 8, { signed: true }) returned -200 instead of 56). This diverged from typed-array coercion.