📅 Original date posted:2015-08-19
📝 Original message:On Wed, Aug 19, 2015 at 2:24 PM, Tier Nolan via bitcoin-dev
<bitcoin-dev at lists.linuxfoundation.org> wrote:
> On Wed, Aug 19, 2015 at 2:15 PM, Btc Drak via bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org> wrote:
>> What problem am I missing if we just mask of the offending bits. For my own project which uses auxpow (and thus has weird nVersion), I also used the bitmasking method to get rid of auxpow version bits before making the standard integer comparisons to deploy BIP66 using IsSuperMajority():
>>
>> if ((block.nVersion & 0xff) >= 4 && CBlockIndex::IsSuperMajority(...)) { //...}
>
> What if version number 257 is used in the future? That would appear to be a version 1 block and fail the test.
To clarify this is the code example for how the same problem occurs
with auxpow bits when running a an IsSuperMajority() softfork and how
it's solved in that instance.
In our case for Bitcoin Core, option 2 we use nVersion=8, apply a
bitmask of 0xdffffff8 thus:
if ((block.nVersion & ~0x20000007) >= 4 &&
CBlockIndex::IsSuperMajority(...)) { //...}
With nVersion=8, but using comparison >=4 allows us to recover the
bit later, assuming we want it (otherwise we use version >=8).
This should, unless I am missing something, be forward compatible with
future softforks. My understanding was if "versionbits softfork" code
is not ready by the time we're ready for the deployment,
IsSuperMajority() would be acceptable; and this is how we could deploy
it in the wake of the XT developers' carelessness.
Btc Drak [ARCHIVE] /
npub1lh…zg7ed
2023-06-07 17:36:59
in reply to nevent1q…5900
Author Public Key
npub1lhe3qfx2q5m7mq5d39waepf9lzhsy0cdey66svn63fyk6rt6n7ps7zg7edPublished at
2023-06-07 17:36:59Event JSON
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"content": "📅 Original date posted:2015-08-19\n📝 Original message:On Wed, Aug 19, 2015 at 2:24 PM, Tier Nolan via bitcoin-dev\n\u003cbitcoin-dev at lists.linuxfoundation.org\u003e wrote:\n\u003e On Wed, Aug 19, 2015 at 2:15 PM, Btc Drak via bitcoin-dev \u003cbitcoin-dev at lists.linuxfoundation.org\u003e wrote:\n\u003e\u003e What problem am I missing if we just mask of the offending bits. For my own project which uses auxpow (and thus has weird nVersion), I also used the bitmasking method to get rid of auxpow version bits before making the standard integer comparisons to deploy BIP66 using IsSuperMajority():\n\u003e\u003e\n\u003e\u003e if ((block.nVersion \u0026 0xff) \u003e= 4 \u0026\u0026 CBlockIndex::IsSuperMajority(...)) { //...}\n\u003e\n\u003e What if version number 257 is used in the future? That would appear to be a version 1 block and fail the test.\n\nTo clarify this is the code example for how the same problem occurs\nwith auxpow bits when running a an IsSuperMajority() softfork and how\nit's solved in that instance.\n\nIn our case for Bitcoin Core, option 2 we use nVersion=8, apply a\nbitmask of 0xdffffff8 thus:\n\n if ((block.nVersion \u0026 ~0x20000007) \u003e= 4 \u0026\u0026\nCBlockIndex::IsSuperMajority(...)) { //...}\n\nWith nVersion=8, but using comparison \u003e=4 allows us to recover the\nbit later, assuming we want it (otherwise we use version \u003e=8).\n\nThis should, unless I am missing something, be forward compatible with\nfuture softforks. My understanding was if \"versionbits softfork\" code\nis not ready by the time we're ready for the deployment,\nIsSuperMajority() would be acceptable; and this is how we could deploy\nit in the wake of the XT developers' carelessness.",
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