[General] zksync-foundry: Some addresses revert, why?

[PatrickAlphaC]

Environment

Testnet

Provide a brief description of the functionality you're trying to implement and the issue you are running into.

I am running the following code in foundry-zksync to find out in my tests when I'm running against a zksync environment vs. when I'm not, and I think I'm close to figuring it out. I have the following code:

    function testMe() public {
        uint256 value = 1;
        // https://docs.zksync.io/build/developer-reference/differences-with-ethereum.html#call-staticcall-delegatecall
        // sending native ETH is not supported on zkSync
        // You have to call the system contract to do so
        for (uint256 i = 0; i < 10; i++) {
            address target = address(uint160(i));
            bool success;
            assembly {
                success := call(gas(), target, value, 0, 0, 0, 0)
            }
            if (!success) {
                console.log(i);
            }
        }
    }

When I test this without the --zksync flag in foundry (via forge test --mt testMe -vvvv), I get an output like:

[PASS] testMe() (gas: 9079256848778908132)
Logs:
  9

Traces:
  [9079256848778908132] InteractionsTest::testMe()
    ├─ [0] 0x0000000000000000000000000000000000000000::fallback{value: 1}()
    │   └─ ← ()
    ├─ [3000] 0x0000000000000000000000000000000000000001::fallback{value: 1}()
    │   └─ ← ()
    ├─ [60] PRECOMPILES::sha256{value: 1}(0x)
    │   └─ ← 0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
    ├─ [600] PRECOMPILES::ripemd{value: 1}(0x)
    │   └─ ← 0x0000000000000000000000009c1185a5c5e9fc54612808977ee8f548b2258d31
    ├─ [15] PRECOMPILES::identity{value: 1}(0x)
    │   └─ ← ()
    ├─ [200] 0x0000000000000000000000000000000000000005::fallback{value: 1}()
    │   └─ ← ()
    ├─ [150] 0x0000000000000000000000000000000000000006::fallback{value: 1}()
    │   └─ ← 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
    ├─ [6000] 0x0000000000000000000000000000000000000007::fallback{value: 1}()
    │   └─ ← 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
    ├─ [45000] PRECOMPILES::ecpairing{value: 1}()
    │   └─ ← 0x0000000000000000000000000000000000000000000000000000000000000001
    ├─ [0] 0x0000000000000000000000000000000000000009::fallback{value: 1}()
    │   └─ ← EvmError: PrecompileError
    ├─ [0] console::log(9) [staticcall]
    │   └─ ← ()
    └─ ← ()

This output makes sense, as (almost) all of these are precompiles, and the only failing precompile is 0x09 which makes sense, because that precompiles fails on invalid input.

However, running this with the --zksync flag, gives me a different output.

[PASS] testMe() (gas: 326597)
Logs:
  3
  4
  5
  8
  9

Traces:
  [326597] InteractionsTest::testMe()
    ├─ [0] 0x0000000000000000000000000000000000000000::fallback{value: 1}()
    │   └─ ← ()
    ├─ [0] 0x0000000000000000000000000000000000000001::fallback{value: 1}()
    │   └─ ← ()
    ├─ [0] PRECOMPILES::sha256{value: 1}(0x)
    │   └─ ← 0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
    ├─ [0] PRECOMPILES::ripemd{value: 1}(0x)
    │   └─ ← ()
    ├─ [0] console::log(3) [staticcall]
    │   └─ ← ()
    ├─ [0] PRECOMPILES::identity{value: 1}(0x)
    │   └─ ← ()
    ├─ [0] console::log(4) [staticcall]
    │   └─ ← ()
    ├─ [0] 0x0000000000000000000000000000000000000005::fallback{value: 1}()
    │   └─ ← EvmError: Revert
    ├─ [0] console::log(5) [staticcall]
    │   └─ ← ()
    ├─ [0] 0x0000000000000000000000000000000000000006::fallback{value: 1}()
    │   └─ ← 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
    ├─ [0] 0x0000000000000000000000000000000000000007::fallback{value: 1}()
    │   └─ ← 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
    ├─ [0] PRECOMPILES::ecpairing{value: 1}()
    │   └─ ← ()
    ├─ [0] console::log(8) [staticcall]
    │   └─ ← ()
    ├─ [0] 0x0000000000000000000000000000000000000009::fallback{value: 1}()
    │   └─ ← EvmError: Revert
    ├─ [0] console::log(9) [staticcall]
    │   └─ ← ()
    └─ ← ()

In this output, 0x03, 0x04, 0x05, 0x08, and 0x09 all error. Why is that?

Repo Link (Optional)

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Additional Details

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[PatrickAlphaC]

After comparing addresses, I think I figured it out.

https://docs.zksync.io/build/developer-reference/differences-with-ethereum.html#precompiles

The erroring addresses are the precompiles that zkSync does not support. I'm assuming zkSync just reverts when unsupported precompiles are called?

[bxpana]

Following up on this one yes, ZKsync reverts when an unsupported precompile is called.