Find slot of private variable

Question

How do I find the slot of a private variable?

I know that Foundry has the method stdstorage.sig(), but that only works for variables with public getters, so private ones are out of scope.

Thanks!

Working on foundry, but thanks for the HH reply. @ZartajAfser — dNyrM, Nov 13 at 10:41

merkleplant · Accepted Answer · 2023-11-13 07:20:51Z

1

Forge provides the inspect command to get specialized information about a smart contract.

Printing a contract's storage layout is achieved via:

forge inspect <Contract> storage --pretty

Note that <Contract> is the path to the contract's file plus the contract's name, eg src/Counter.sol:Counter.

The --pretty flag prints the storage layout in a more readable format. Without it, the command outputs the storage layout in json format.

answered Nov 13 at 7:20

merkleplant

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How do you feed the address of an already deployed contract to the inspect command? Don't see the flag for it in the docs
– dNyrM
Nov 13 at 10:40
If the contract is verified on etherscan, you can use cast etherscan-source <address> --chain <chainId>. See here for more info.
– merkleplant
Nov 13 at 10:51
That worked! Thanks.
– dNyrM
Nov 13 at 11:02
1

also you can use services like evm.storage for deployed contracts
– crystalbit
Nov 13 at 11:11
While external services like evm.storage can be used, keep in mind that they only support a subset of EVM chains. Foundry itself is chain-independent and the above proposed solution works for every EVM chain. However, the etherscan trick also only works for EVM chains with an Etherscan instance.
– merkleplant
Nov 14 at 7:18

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