Solidity – Does Function Revert If ERC20 or ERC721 transferFrom Fails?

erc-20erc-721solidity

I'm having some security doubts and confusion about the case of reverts. As I found, the whole changes of a function are reverted if the native transfer function fails. But what about the ERC721 and ERC20's transfer, transferFrom, safeTransferFrom?

For example:

  1. If (1) or (2) fails, does the function breaks out and revert the offer.isAccepted?

  2. If (2) fails, is weth transfer and therefore the whole function reverted?

    function acceptBid(uint256 _offerId) public nonReentrant {
Offer storage offer = offers[_offerId];

IERC20 weth = IERC20(0xc778417E063141139Fce010982780140Aa0cD5Ab);
IERC721 nftContract = IERC721(offer.nftContractAddress);

address nftOwner = nftContract.ownerOf(offer.tokenId);

offer.isAccepted = true; // *
weth.transferFrom(
    address(offer.userAddress),
    payable(msg.sender),
    offer.price
); // (1)

nftContract.transferFrom(
    address(this),
    offer.userAddress,
    offer.tokenId
); // (2)

emit AcceptedOffer();}

Best Answer

The smart contract methods are executed in a transactional way. This means, if any of revert, require or failed assert is executed, then the whole transaction is meaned to revert, rolling back any changes made.

So:

  • When weth.transferFrom reverts, offer.isAccepted will be cleared
  • When nftContract.transferFrom reverts, weth.transferFrom will be rolled back and offer.isAccepted will be cleared.
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