Solidity – Using TranferFrom in Delegate Call with ERC20 Tokens

erc-20erc-20-approveremixsolidity

I have an ERC20 test contract, also I did multicall with delegatecall function instead of call.
I have a three accounts: account1, account2, and account3.
account1 can spend tokens from account2 (I did transaction here, and this is works)

Then I tried to send the same transaction with multicall contract, and I got an error: ERC20: insufficient allowance, here a callstack

So I see in both transactions allowance call, but in the second transaction I see allowance as 0. How to fix that? and why that happened?

Best Answer

Delegatecall requires target and source to have compatible storage layouts. You'll be executing the target's bytecode in the source contract's storage. If the Multicall contracts delegatecalls to the ERC20 it will not work as you are expecting

they don't have compatible layouts,
it will be modifying the Multicall storage and not the ERC20 storage.

Check the answer for the Difference between CALL, CALLCODE and DELEGATECALL to understand the details.

Related Solutions

ERC-20 – Approve ERC20 Token Inside a Contract Function

Thus, to approve my contract to spend token for some tokens' holder, the msg.sender in the approve function of ERC20 should be the token holder, hence the token holder should call the function directly on the client side without passing through a contract because the contract can't impersonate that user.

You are correct on every point !

The ERC-20, ERC-721 will only allow a holder to directly approve a spender for obvious logic and security reasons.

erc-20 – How to Resolve ERC20: Insufficient Allowance Error

msg.sender will have to approve GameItem smart contract address before transferFrom can be initialized to work, you were trying to transfer from the sender and the sender is yet to approve the contract address it won't work, the declaration that you here

GXGToken.approve(msg.sender,_amount);

GXGToken token has an approve function, the user must interact with GXGToken token contract address direct and use it approval function to approve GameItem smart contract address before the user (address) before the user(address) will call the function.

approve(GameItem smart contract address, _amount);

your intention was that it would automatically set the msg.sender to approve the GameItem smart contract address, it doesn't work that way.

the solution here can explain the use case of Approval and transferFrom excplicitly: What is the use case of transferFrom function in ERC20 token contract?

Best Answer

Related Solutions

ERC-20 – Approve ERC20 Token Inside a Contract Function

erc-20 – How to Resolve ERC20: Insufficient Allowance Error

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