py/objarray: Update slice data only if necessary. - #19658
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This commit skips modifications to array slices length information if there is no change in the slice size. For simplicity reasons both the slice size and the slice free items count were always updated on every memory access. This could be a problem if the slice object is pre-built and located in ROM, as some microcontrollers may trigger a bus error or other exceptions in that case. These changes make the update conditional, occurring only if the slice size has been changed. Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
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Coverage 98.58% 98.58%
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Lines 23322 23323 +1
Branches 5 5
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This commit expands the test for `machine.mem_backup` to also include read and write operations through a memoryview slice. Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
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Summary
This PR skips modifications to array slices length information if there is no change in the slice size.
For simplicity reasons both the slice size and the slice free items count were always updated on every memory access. This could be a problem if the slice object is pre-built and located in ROM, as some microcontrollers may trigger a bus error or other exceptions in that case.
That is true at least in the ESP32 port, in which the memoryview object is located in ROM, causing issues like #19655 for example.
I've also added some slice read/write to the relevant test.
This closes #19655.
Testing
The
basicsandextmodtest suites pass on an ESP32S3.Octoprobe will hopefully test the rest of the ports :)
Trade-offs and Alternatives
Since the slice update is now conditional there may be a minor size increase.
Generative AI
I did not use generative AI tools when creating this PR.