On Tue, Oct 29, 2013 at 10:32 PM, Mike Hearn <mike@plan99.net> wrote:

> Yes, exactly. That's the point. As you well know I think the whole
> soft-fork mechanism is wrong and should not be used. If the rules change,
> your node is *supposed* to end up on a chain fork and trigger an alert to
> you, that's pretty much the whole purpose of Bitcoin's design. Undermining
> that security model is problematic.
>

But if you are getting soft-forked recent versions of the reference
implementation WILL alert you; see this code in main.cpp:

        if (nUpgraded > 100/2)
            strMiscWarning = _("Warning: This version is obsolete, upgrade
required!");

That is, if more than half of the last 100 blocks are up-version, warn.
 block.version is part of the block header, so SPV clients can (and
probably should) do the same.

There are also warnings if you are forked, and, most recently, warnings if
there is a high-work alternative fork.

-- 
--
Gavin Andresen