Repricing for trie-size-dependent opcodes (EIP1884)

[holiman]

This EIP proposes repricing certain opcodes, to obtain a good balance between gas expenditure and resource consumption.

[nicksavers]

Assets can be placed in the /assets directory. They'll need to be put into another directory with the name of the EIP. You can use #1884 for this.

[holiman]

Thanks, I moved the assets now

[nicksavers]

Apart from a technical specification, it is the place to link to clients that have implemented the change.

[nicksavers]

The first 'Opcode' seems redundant here.

[k06a]

I afraid increasing SLOAD opcode gas cost may break some existing deployed smart contracts. They can perform limited gas subcalls, which will not fit after this change.

[axic]

Please leave this comment on the discussion-to URL.

[k06a]

@axic thanks: https://ethereum-magicians.org/t/opcode-repricing/3024/10?u=k06a

[cupOJoseph]

The reentrancy attacks are going to be crazy when this launches. I can't believe there wasnt more discussion on this.

[holiman]

The reentrancy attacks are going to be crazy when this launches. I can't believe there wasnt more discussion on this.

Why would this trigger reentrancy attacks?

[cupOJoseph]

The gas price increase will effect fallback functions called when a contract receives ether.

https://gist.github.com/ritzdorf/1c6bd72955391e831f8a397d3152b4e0

The current execution of the fallback function in case of a send/transfer consumes 1759 gas. It contains one SLOAD due to isDepositable(). Therefore, it will break with EIP-1884.

https://etherscan.io/tx/0x14a4a43b4e9759aac86bb0ae7e5926850406ff1c43ea571239563ff781474ae0

Based on this research I believe the gas price changes effecting previously deployed contracts is a mistake.

[holiman]

But how does that relate to reentrancy attacks?

[jdetychey]

Hello @holiman
I believe @jschiarizzi is pointing out that while fallback function execution breaks due to repricing it might create reentrancy in a context where for example Alice calls contract A, contract A sends Eth to contract B, contract B fallback execute code and break, Alice now reenters by calling contract A again.