Remove Frontier canaries

[bobsummerwill]

It appears that geth removed the Frontier canaries, but this work was neglected for eth, as highlighted by @theymos (thank you!) in https://www.reddit.com/r/Bitcoin/comments/4k2kki/stalling_time_for_what_bitcoins_needs_segwit_or/d3comb5.

• geth - Fixed in core, miner: remove Frontier canary go-ethereum#2416
• eth - Fixed in Remove Frontier canaries, which were left in by mistake. libethereum#259
• pyethapp - Fixed in remove Frontier canary pyethapp#134
• ethereumjs-lib - Never had the functionality
• Parity - Never had the functionality
• ruby-ethereum - Fixed in cryptape/ruby-ethereum@f90b8b3
• ethereumH - waiting to hear back
• ethereum(J) - waiting to hear back

geth removal happened on April 4th in ethereum/go-ethereum#2416 (as pinpointed by @karalabe), and as geth has ~99% of client market share, any triggering of the canaries in eth would only kill the eth clients.

But no two ways about it, this was a fuck-up and we should fix it right now.

Not sure if pyethapp had the canary too? Or other clients too? They should be fixed too.

Search for shouldSeal and canaries in webthree-umbrella to find the references.

Here are the key line which needs fixing:

https://github.com/ethereum/libethereum/blob/develop/libethashseal/Ethash.cpp#L297

[bobsummerwill]

Though actually, this likely affects ALL miners, doesn't it?

All the "canary folk" could do by triggering it would be to punch themselves in the face, because the workaround is to the remove the one-liner. It is a very shallow "shutdown switch".

[bobsummerwill]

^ Not a problem to the miners, says @karalabe.