At the moment, bitcoin does not verify that the outscripts of transactions are syntactically valid. Thus it is possible to create a transaction with junk in it's outscripts and get it into the block chain. No one could spend such coins (at least until the opcodes change). The question is, should such garbage transactions simply be rejected out of hand instead?
I believe the main blockchain has no such garbage outscripts in it yet, so this change could be effected now without harming the chain.
One person's garbage is another person's gold.
And the blockchain DOES have garbage transactions in it-- see block 71036. Those garbage transactions partly insipired the change so that non-standard transactions ARE rejected by clients and mainline miners.
I'm going to close this; if you have a specific proposal, please discuss it on the forums.
You are wrong. All the scripts in Block 71036 are syntactically valid.
@roconnor is talking about syntactic validity, not about whether the script is a) standard or b) evaluates to true for a particular/possible input. For example if it'd contain unknown opcodes, or opcodes that require additional databytes at the end of the output script.
Benefit of allowing anything is it will make upgrading easier.
I don't see any harm in leaving the TxOuts unparsed until they're spent. I suppose you could arge that syntactically incorrect garbage could bloat the block chain, but it is almost as easy to create syntactically CORRECT garbage to bloat up the chain.
As long as you understand, I also don't see any harm either. I'll close.
Upon further inspection, I think that the TxOut scripts are parsed before being included in the block chain. Because of the way the TxOut structure is serialized the length of the script is included in the serialization. The length of the script is pretty much impossible to compute without parsing the script. (I had erroneously thought it was the length in bytes of the serialized script that was put into the serialized transaction, but it is the length of the script.)
Ah no, I was right origianlly, TxOut scripts are unparsed.
Fun fact, the outputs of this transaction seem to be the first syntactically incorrect scripts of the blockchain: https://blockchain.info/tx/ebc9fa1196a59e192352d76c0f6e73167046b9d37b8302b6bb6968dfd279b767?format=json made in 2013, e.g. "script":"01". It's fun to see people throw away 3000 dollars for run.