[6.2] CastOptimizer: don't assume dynamic casts from ObjectiveC classes to unrelated classes will fail #81251
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Contributor
eeckstein
commented
May 2, 2025
eeckstein
commented
- Explanation: In case of ObjectiveC classes, the runtime type can differ from its declared type. Therefore a cast between (compile-time) unrelated classes may succeed at runtime. It turned out that this kind of runtime vs. formal type mismatch appears quite often in real world code. This change disables ObjectiveC class casts in the cast optimizer which makes the generated code in release builds behave the same way as in debug builds.
- Risk: low: It's a simple change which cast optimizer more conservative when dealing with ObjectiveC classes.
- Testing: Tested by lit tests
- Issue: rdar://149810124
- Reviewer: @mikeash , @tbkka
- Main branch PR: CastOptimizer: don't assume dynamic casts from ObjectiveC classes to unrelated classes will fail #81203
…unrelated classes will fail In case of ObjectiveC classes, the runtime type can differ from its declared type. Therefore a cast between (compile-time) unrelated classes may succeed at runtime. rdar://149810124
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@swift-ci test linux |
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tbkka
approved these changes
May 5, 2025
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