Fix large, backwards, memory.copy with fuel/epochs#13577
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This commit fixes a bug in the previous refactorings of `memory.copy` or other bulk copy instructions. Notably when fuel/epochs were enabled the operation was chunked up to check fuel between each operation, but the advancement of what to do unconditionally went forwards. When a backwards copy is required this means that data could get corrupted if the src/dst regions are overlapping. The fix here is to setup a separate backwards-copy loop which handles this case so the fuel/epoch-metered copy goes either backwards or forwards depending on what's being copied.
alexcrichton
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Jun 6, 2026
* Fix large, backwards, `memory.copy` with fuel/epochs (#13577) This commit fixes a bug in the previous refactorings of `memory.copy` or other bulk copy instructions. Notably when fuel/epochs were enabled the operation was chunked up to check fuel between each operation, but the advancement of what to do unconditionally went forwards. When a backwards copy is required this means that data could get corrupted if the src/dst regions are overlapping. The fix here is to setup a separate backwards-copy loop which handles this case so the fuel/epoch-metered copy goes either backwards or forwards depending on what's being copied. * Fix corrupted pooling allocator state on OOM (#13579) This commit fixes an issue where if the pooling allocator generated OOM at just the right time then it would leave the pooling allocator in a corrupt state where the instance count was incremented, never decremented. This additionally fixes a separate issue where if an OOM happened just a bit later then it would mean that tables/memories from the pooling allocator would leak and not be properly destroyed within the allocator, leaking their slots.
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This commit fixes a bug in the previous refactorings of
memory.copyor other bulk copy instructions. Notably when fuel/epochs were enabled the operation was chunked up to check fuel between each operation, but the advancement of what to do unconditionally went forwards. When a backwards copy is required this means that data could get corrupted if the src/dst regions are overlapping. The fix here is to setup a separate backwards-copy loop which handles this case so the fuel/epoch-metered copy goes either backwards or forwards depending on what's being copied.