Prevent deserialization of infinitely-recursive CircuitOperations #4304
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Part of #3634. |
viathor
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CirqBot
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Jul 13, 2021
Fixes #4304. To be precise, this was already working: because the deserializer does not append constants to the `deserialized_constants` map until it finishes deserializing them, it is naturally unable to deserialize a recursive subcircuit. This PR just adds the test. Note that the _serializer_ will still happily attempt (and fail) to serialize CircuitOperations that exhibit infinite recursion. We allow this because `CircuitOperation` is an immutable type; unless you intentionally circumvent the safeguards that prevent mutation (as shown in the test), it is not possible to define a `CircuitOperation` that contains itself.
rht
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May 1, 2023
Fixes quantumlib#4304. To be precise, this was already working: because the deserializer does not append constants to the `deserialized_constants` map until it finishes deserializing them, it is naturally unable to deserialize a recursive subcircuit. This PR just adds the test. Note that the _serializer_ will still happily attempt (and fail) to serialize CircuitOperations that exhibit infinite recursion. We allow this because `CircuitOperation` is an immutable type; unless you intentionally circumvent the safeguards that prevent mutation (as shown in the test), it is not possible to define a `CircuitOperation` that contains itself.
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Is your feature request related to a use case or problem? Please describe.
Immutability of
CircuitOperations prevents users from accidentally defining self-referencingCircuitOperations, but it is still possible to intentionally construct such an operation.Describe the solution you'd like
Before we enable the use of
CircuitOperations in QCS, we must block infinitely-recursiveCircuitOperations from being deserialized. The deserializers should include a check to guard against this.What is the urgency from your perspective for this issue? Is it blocking important work?
P1 - I need this no later than the next release (end of quarter)
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