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[hot_reload] Don't look at delta method table rows #57798

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merged 2 commits into from
Aug 20, 2021

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The issue is that the ParamList column in EnC deltas is a "suppressed column" that has the value 0. So when a method is updated if we use the value directly, we will break, for example - mono_metadata_get_param_attrs which expects a non-zero index in that column.

CoreCLR solves this by having a set of suppressed columns that are never updated by deltas. (CoreCLR's model is to directly mutate the tables of the baseline image). In Mono we can eventually do the same thing by writing the value from the previous generation into the current delta's row. But right now since we don't allow parameter modifications, and the only column on a Method table that we allow to be modified is the RVA - which we look up specially - we can just always return the baseline image row for the method table.

Fixes #57643

Call a method for the first time after an update has been applied to it.

This will check that the interpreter or JIT does not have to rely on cached
information from the baseline (about the method signature, for example) and
that it can compute it from the delta.
The issue is that the ParamList column in EnC deltas is a "suppressed column"
that has the value 0.  So when a method is updated if we use the value
directly, we will break, for example - `mono_metadata_get_param_attrs` which
expects a non-zero index in that column.

CoreCLR solves this by having a set of suppressed columns that are never
updated by deltas.  (CoreCLR's model is to directly mutate the tables of the
baseline image).  In Mono we can eventually do the same thing by writing the
value from the previous generation into the current delta's row.  But right now
since we don't allow parameter modifications, and the only column on a Method
table that we allow to be modified is the RVA - which we look up specially - we
can just always return the baseline image row for the method table.

Fixes dotnet#57643
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I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

@lambdageek lambdageek added the area-EnC-mono Hot Reload for WebAssembly, iOS/Android, etc label Aug 20, 2021
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/backport to release/6.0-rc1

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Started backporting to release/6.0-rc1: https://github.com/dotnet/runtime/actions/runs/1149439918

@lambdageek lambdageek merged commit 53cafdd into dotnet:main Aug 20, 2021
@ghost ghost locked as resolved and limited conversation to collaborators Sep 19, 2021
@lambdageek lambdageek deleted the fix-gh-57643 branch March 19, 2022 16:45
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[hot_reload] Calling a method for the first time after an update crashes the app
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