On Wednesday, August 17, 2016 3:02:53 AM Johnson Lau via bitcoin-dev wrote:
> To completely replicate the original behaviour, one may use:
> "DEPTH TOALTSTACK IFDUP DEPTH FROMALTSTACK NUMNOTEQUAL IF 2DROP {if script}
> ELSE DROP {else script} ENDIF"This is much uglier than expected. IMO if that's the best workaround for the current behaviour, people should just use "OP_1 OP_EQUAL OP_IF" when/if they need to avoid malleability issues. I suspect most cases OP_IF would be used, you really want to accept any non- zero value. For example, the HTLC script I posted on the list about not long ago (OP_IF operates on the result from OP_SIZE). Counter-examples would be BIP 124, the examples in BIP 65 and BIP 112, but I note all of these could be just as easily done without the explicit boolean being fed to the OP_IF (you'd need an OP_DUP to keep the value, so it wouldn't reduce the byte-size). Of course, as long as we're talking about a softfork activating together with segwit, and only having effect in segwit scripts... there's no reason we can't add whatever opcodes we need so long as it gets done before 0.13.1. I suggest OP_CASTTOBOOL and OP_DUPASBOOL would be two good candidates if we make OP_IF stricter. There's also the possibility of adding an OP_RETAINIF which behaves as the current OP_IF, except not popping the conditional value off the stack. But perhaps this is getting too complicated for testing in time for segwit... Luke _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
