On Tuesday 19 September 2017 12:46:30 AM Mark Friedenbach via bitcoin-dev wrote: > After the main discussion session it was observed that tail-call semantics > could still be maintained if the alt stack is used for transferring > arguments to the policy script.
Isn't this a bug in the cleanstack rule? (Unrelated...) Another thing that came up during the discussion was the idea of replacing all the NOPs and otherwise-unallocated opcodes with a new OP_RETURNTRUE implementation, in future versions of Script. This would immediately exit the program (perhaps performing some semantic checks on the remainder of the Script) with a successful outcome. This is similar to CVE-2010-5141 in a sense, but since signatures are no longer Scripts themselves, it shouldn't be exploitable. The benefit of this is that it allows softforking in ANY new opcode, not only the -VERIFY opcode variants we've been doing. That is, instead of merely terminating the Script with a failure, the new opcode can also remove or push stack items. This is because old nodes, upon encountering the undefined opcode, will always succeed immediately, allowing the new opcode to do literally anything from that point onward. Luke _______________________________________________ bitcoin-dev mailing list firstname.lastname@example.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev