[release/11.0-rc1] Reject malformed UTF-8 number separators - #132471
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tannergooding merged 1 commit intoAug 19, 2026
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`MatchChars<TChar>` currently applies UTF-16 NBSP normalization directly to UTF-8 bytes. This allows a standalone `0xA0` continuation byte to match an ASCII space in a configured number separator, so malformed UTF-8 can parse successfully. Restrict the compatibility normalization to UTF-16 while preserving exact UTF-8 matching. Regression tests cover both the CoreLib numeric parser and the separate `BigInteger` shared-source instantiation. This regressed in #123783. > [!NOTE] > This pull request description was drafted by GitHub Copilot. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Tagging subscribers to this area: @dotnet/area-system-numerics |
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CC. @jeffhandley, @artl93 |
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Core functionality regression. Approved.
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Backport of #132417 to release/11.0-rc1
/cc @tannergooding
Customer Impact
Malformed UTF-8 can be accepted as valid numeric input when a standalone
0xA0continuation byte occurs where a configured number-format symbol contains an ASCII space. The expected behavior is to reject the malformed input. This affects culture-aware parsing across the CoreLib numeric types and the separateBigIntegershared-source instantiation.Regression
Introduced by #123783 in February 2026. That change intentionally made space/NBSP normalization bidirectional for UTF-16, but inadvertently applied Unicode normalization to individual UTF-8 bytes as well.
Testing
Regression tests were added for both the CoreLib numeric parser (
Int32) andBigInteger; each failed before the fix and passed afterward. A checked CoreLib build succeeded, as did the completeSystem.Runtime.Testssuite (77,366 tests) andSystem.Runtime.Numerics.Testssuite (8,426 tests).The issue was missed because #123783 tested only UTF-16 input even though the modified shared implementation also instantiates over one-byte UTF-8 elements.
Risk
Low. The production change restricts Unicode compatibility normalization to the UTF-16 specialization. Exact UTF-8 matching is unchanged, malformed mismatched bytes are rejected, and the intended bidirectional UTF-16 behavior remains intact. Both shared-source instantiations and their complete test suites were validated.
Note
This pull request description was drafted by GitHub Copilot.