Avoid using object_gennum for objects that could come from frozen segments #65174
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Tagging subscribers to this area: @dotnet/gc Issue Detailsnull
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mangod9
approved these changes
Feb 11, 2022
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can you please put in some description of the problem, or at least a link to an issue that this is fixing? |
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This was related to the test failures in frozen segments in a test that was recently added. Here is the failure: |
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thanks. maybe it wasn't happening because you were not running a debug build? NextObj is only called on debug builds unless you specifically ask to do verification on release. the only other case is from byref validation - I dunno who asks to validate these. |
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The function we are changing is
GCHeap::NextObj, which is a public API that could be called externally.The
objectcould be any managed object, potentially an object coming from a frozen segment.The code, as is, will call the
object_gennumfunction, which will fail if an object is not in the region's range as follow:object_gennum->get_region_gen_num->region_ofwould return an invalidheap_segmentpointer.Attempting to dereference it to get the generation number would fail.
Looking in retrospect, I have no idea why the test case wasn't failing before under regions, it should be always crashing.