zkvm: non-copyable Program, Expression and Constraint #304
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Can you add a test showing that a contract trying to duplicate a program fails? (The tests checking that normal transactions succeed will now check that normal program outputting succeeds, but there is no failure case check here). |
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@cathieyun added tests for Program, Expression and Constraint. Expanded the scope of this PR to extend to Expressions and Constraints. |
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| ### Data type | ||
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| A _data type_ is a variable-length byte array used to represent signatures, proofs and programs. | ||
| A _data type_ is a variable-length byte array used to represent [commitments](#pedersen-commitment), [scalars](#scalar), signatures and proofs. |
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Repeating some feedback from an earlier round of review on this spec: "type" is being used in a confusing way here. You can talk about "the data type" or "an instance of type data" but not "a data type." Consider:
An object of the data type is a variable-length byte array...
(Same thing with "program type" below.)
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How about renaming it into String in some other PR?
| @@ -1298,29 +1314,33 @@ Fails if the `prevoutput` is not a [data type](#data-type) with exact encoding o | |||
| _items... predicate_ **output:_k_** → ø | |||
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| 1. Pops [`predicate`](#predicate) from the stack. | |||
| 2. Pops `k` items from the stack. | |||
| 2. Pops `k` [portable items](#portable-types) from the stack. | |||
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If the top k items includes a non-portable item, is that an error or is it skipped? I know you intend it to be an error, but I think it's a little ambiguous as written.
I think the original wording ("Pops k items from the stack") plus the new "fails if" text below is fine.
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| #### contract | ||
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| _items... pred_ **contract:_k_** → _contract_ | ||
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| 1. Pops [predicate](#predicate) `pred` from the stack. | ||
| 2. Pops `k` items from the stack. | ||
| 2. Pops `k` [portable items](#portable-types) from the stack. |
| @@ -1362,45 +1382,47 @@ _contract(P) proof prog_ **call** → _results..._ | |||
| 7. Places the [payload](#contract-payload) on the stack (last item on top). | |||
| 8. Set the `prog` as current. | |||
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| Fails if the top two items are not [data](#data-type) or the third from top is not a [contract](#contract-type). | |||
| Fails if: | |||
| 1. `prog` is not a [program type](#program-type), | |||
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Same comment about "a program type," "a data type," and "a contract type." I'd much prefer "a program," "a data item," and "a contract."
Co-Authored-By: Bob Glickstein <bobg@users.noreply.github.com>
This adds a non-copyable type
Programwhich is separate fromDatatype. Instructionscallanddelegateexpect Program type, instructiondupfails if used with a Program.Also, the
ExpressionandConstraintare made non-copyable and non-droppable. Variables are left to be copyable, so they can participate in constraints and then be used in the construction of Values.Rationale is covered in #301 & #306.
Closes #301
Closes #306