Improved ptr permission implications #1373
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added 2 commits
July 8, 2021 17:32
… that precisely match the offset of the ptr perm being proven
eddywestbrook
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subsystem: heapster
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PR: ready to merge
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This commit changes implication for ptr perms to prioritize using LHS permissions that precisely match the offset of the ptr perm being proven. That is, if we are proving something like
ptr((W,0) |-> p1) * array(8, <z8, *8, [(W,0) |-> int64<>], []) -o ptr((W,0) |-> p2)the old approach would consider using the
arraypermission at index -1 as one way to perform the proof. The new way sees that there is indeed aptrperm on the LHS with the correct offset, so ignores any other possibilities.This PR also adds the clearbufs example which requires this change for its type-checking.