Tachyon: Allow multiple OP_RETURN outputs in a transaction

After the Tachyon upgrade, a standard transaction can now use any number of data carrier outputs, as long as the total script size of these outputs does not exceed the pre-existing limit of 223 bytes. The number 223 remains user-configurable (-datacarriersize=<n>).

Cumulative size of OP_RETURN outputs is counted in a CScript::size_type (currently uint32_t) and checked only once at the end (for optimal performance for standard transactions). Because of the consensus and standardness transaction size limits, there is no risk of overflow. The new per-transaction size check makes the old per-output size check redundant, also before the upgrade, and hence the latter has been removed.

Specification effort: https://bitcoincashresearch.org/t/multiple-op-returns-this-time-for-real/315

Includes tests:

• Unit test for both pre-upgrade and post-upgrade standardness logic.
• Functional test for activation, based on the OP_RETURN limit increase in the Monolith (May 2018) upgrade (removed in commit 9e563fa4).

After the upgrade activates, the pre-upgrade logic and the functional test can be removed.

Test plan: ninja check check-functional

changed milestone to %v23.0.0

added HODL GANG for-review release-blocking standardness labels

added 1 commit

• a8930cae - Tachyon: Allow multiple OP_RETURN outputs in a transaction

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mentioned in merge request !1117 (merged)

concept ACK

mentioned in issue #256 (closed)

Technical spec: https://github.com/ActorForth/Auction-Protocol/pull/3/files

Reviewed and tested. I have no technical reservations, only a readability nit on the new boolean parameter for IsStandardTx(), as I do not find code calling it to be very clear (due to the "what does true/false mean here?" question it always raises for a reader).

Might be an idea to use the inline commenting syntax that Calin uses for bool constants as parameter values, this is also explicitly suggested in the LLVM coding guidelines from which our current guidelines (doc/developer-notes.md) take their cues.

IsStandardTx(CTransaction(txFrom), reason, /* allowMultipleOpReturn */ false);
IsStandardTx(CTransaction(txFrom), reason, /* allowMultipleOpReturn */ true);

approved this merge request

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• 58ee973d - Tachyon: Allow multiple OP_RETURN outputs in a transaction

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Now uses "Calin syntax"

Ha ha "Calin syntax" -- I actually only do that because that was used by Core in this codebase.. ha ha ha :)

approved this merge request

approved this merge request

removed HODL GANG label

approved this merge request

mentioned in commit fc1dae57

merged

mentioned in merge request bitcoinunlimited/BCHUnlimited!2453 (closed)