Safe Smart Accout Implemented in Yul

Functional Differences

While this implementation strives to be a pure port, there are a couple functional differences with the reference implementation:

• Some view methods are implemented in the fallback handler using simulation techniques (simulateAndRevert) instead of in the account itself.
• Calldata length is not verified in function calls. This is a difference with the Solidity ABI in general, but not a security issue for the account, but may be unexpected if callers make certain (unsafe) assumptions about how contracts react to incorrectly ABI-encoded calls.
• When the fallback handler is address 0, we still call it. The output will be the same, but will do an extra unnecessary CALL. However, the extra code and gas for checking the handler address is non-zero is not worth it as Safes are almost never configured this way in practice, and when they are, shouldn't be called this way anyway.
• getModules reverts if there are more than the default page size of modules.
• simulateAndRevert is payable. It reverts so funds can't be lost.
• We always revert with GS204 on duplicate owners during setup. This is ensured by reversing the order in which we build the linked list.
• setup function is payable.

Benchmarks

	Configuration	EOA	Yul	1.4.1	1.5.0	Gas Improvement	Overhead Improvement
Setup	1 of 1	0	163848	166349	166309	1.50%	1.50%
	1 of 1 + guard	-	163848	166349	166309	1.50%	1.50%
	2 of 2	-	186756	189813	189755	1.61%	1.61%
	3 of 3	-	209652	213265	213189	1.69%	1.69%
	3 of 5	-	255468	260193	260081	1.82%	1.82%
Ether Transfer	1 of 1	21000	55807	58718	58706	4.96%	7.72%
	1 of 1 + guard	-	60558	64502	64535	6.11%	9.07%
	2 of 2	-	62358	65796	65750	5.23%	7.67%
	3 of 3	-	68897	72862	72819	5.44%	7.65%
	3 of 5	-	68909	72850	72819	5.41%	7.60%
ERC20 Transfer	1 of 1	51800	80049	82975	82975	3.53%	9.39%
	1 of 1 + guard	-	84845	88769	88825	4.42%	10.61%
	2 of 2	-	86612	90029	90019	3.80%	8.94%
	3 of 3	-	93164	97109	97089	4.06%	8.71%
	3 of 5	-	93164	97097	97065	4.05%	8.68%
ERC1155 Transfer	1 of 1	53707	82041	84967	84967	3.44%	9.36%
	1 of 1 + guard	-	86874	90810	90842	4.33%	10.61%
	2 of 2	-	88580	92034	92024	3.75%	9.01%
	3 of 3	-	95143	99088	99068	3.98%	8.69%
	3 of 5	-	95143	99100	99080	3.99%	8.72%