[release/8.0.1xx-xcode15.1] [runtime] Fix memory leak with BlockLiteral descriptors. Fixes #20503. #20562

rolfbjarne · 2024-05-06T07:43:20Z

We're using two different functions to atomically decrement a reference count,
the native atomic_fetch_sub and the managed Interlocked.Decrement.

Unfortunately the return value is not the same: atomic_fetch_sub returns the
original value before the subtraction, while Interlocked.Decrement returns
the subtracted value, while our code assumed the functions behaved the same.
This resulted in a memory leak, because we'd incorrectly expect 0 to be
returned from atomic_fetch_sub when the reference count reaches zero, and
thus not detect when the descriptor a block should be freed.

The fix is to update the expected return value from atomic_fetch_sub to be
1 instead of 0.

Fixes #20503.

Backport of #20556.

…n#20503. We're using two different functions to atomically decrement a reference count, the native `atomic_fetch_sub` and the managed `Interlocked.Decrement`. Unfortunately the return value is not the same: `atomic_fetch_sub` returns the original value before the subtraction, while `Interlocked.Decrement` returns the subtracted value, while our code assumed the functions behaved the same. This resulted in a memory leak, because we'd incorrectly expect `0` to be returned from `atomic_fetch_sub` when the reference count reaches zero, and thus not detect when the descriptor a block should be freed. The fix is to update the expected return value from `atomic_fetch_sub` to be `1` instead of `0`. Fixes xamarin#20503.

…se/8.0.1xx-xcode15.1-2024-05-06

vs-mobiletools-engineering-service2 · 2024-05-20T16:53:45Z

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vs-mobiletools-engineering-service2 · 2024-05-20T16:55:07Z

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vs-mobiletools-engineering-service2 · 2024-05-20T17:20:38Z

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vs-mobiletools-engineering-service2 · 2024-05-20T17:27:01Z

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vs-mobiletools-engineering-service2 · 2024-05-21T08:33:16Z

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vs-mobiletools-engineering-service2 · 2024-05-21T09:00:39Z

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vs-mobiletools-engineering-service2 · 2024-05-21T12:20:45Z

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vs-mobiletools-engineering-service2 · 2024-05-22T18:03:35Z

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