Add no-return-data ERC20 support to SafeERC20. #1655
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nventuro
added
feature
4 tasks
frangio
reviewed
Feb 27, 2019
contracts/token/ERC20/SafeERC20.sol
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| * @dev Parses the return value of the last contract call and attempts to return a boolean value out of it. | ||
| */ | ||
| function getBooleanReturnValue() private pure returns (bool result) { | ||
| // We need to use inline assembly here, since it is the only way we can utilize the returndatasize opcode. |
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This is true for the opcode, but we could be using the data byte array returned by call and reading data.length. What do you think?
I don't feel so comfortable having this function use the returndata opcodes because they're like reading from global variables.
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data.length sure, but I'm not sure if there's a convenient way to check for a boolean value stored inside the bytes array.
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Maybe it's a good time to introduce that bytes conversion library. 👀
frangio
reviewed
Feb 28, 2019
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Reimplementation of #1344, based on discussion from there (thanks @k06a for inspiration for the assembly code!).
This adds support to
SafeERC20forERC20contracts that return no value (i.e. those that do nothing on success, and revert/throw when an error occurs). Solidity now performs automatic return data size checks, so prior to this patch those contracts would've caused a revert. We now resort to low level calls to workaround this.I've refactored the mocks and tests in the process, since they were getting a bit out of hand. I tried running the old contract against the updated test suite, and as expected, all tests pass except the ones in the 'with token that returns no boolean values'
describeblock.