The prestateTracer under diffMode does not return all the storage diffs.

[lum7na]

System information

Geth version: 1.14.12
OS & Version: Linux

Expected behavior

Hi! I'm trying to debug the transaction using debug_traceTransaction. I use the built-in prestateTracer and enable diffMode. I notice in the post section of the returned result, an address that should have been modified was ignored.

The following modifications occurred after executing the transaction setRational(-34342247582603709930262480515100532418408549587488298634819624648327228197968,54)

0x0000000000000000000000000000000000000000000000000000000000000000 
 -> 0xb412fa0861bb1532171e2f7e6d88df75e8bb79d4ba10674f506b1d13a2d973b0
0x0000000000000000000000000000000000000000000000000000000000000001
 -> 0x0000000000000000000000000000000000000000000000000000000000000036

The debug_traceTransaction RPC call returned the correct result. However, if I continue to execute the transaction setRational(0,-3686082785242131774829242764878224605745458421934561058325782450253198843211). The state modification should be:

0x0000000000000000000000000000000000000000000000000000000000000000
 -> 0x0000000000000000000000000000000000000000000000000000000000000000
0x0000000000000000000000000000000000000000000000000000000000000001 
 -> 0xf7d9c0469c411e6b7d7863011ce7f3f258685e4ce99f5467f28c3598787722b5

However, debug_traceTransaction only returned one modification in the post section: {'0x0000000000000000000000000000000000000000000000000000000000000001': '0xf7d9c0469c411e6b7d7863011ce7f3f258685e4ce99f5467f28c3598787722b5'}. It ignored the modification of 0x0000000000000000000000000000000000000000000000000000000000000000.

pragma  abicoder v2;

contract TestRational {
  struct Rational { int256 numerator; int256 denominator;  }

  Rational r;

  function getRational() public returns(Rational memory) {
    return r;
  }

  function setRational(int256 num, int256 denom) public {
    require(denom != 0, hex"44656e6f6d696e61746f722063616e6e6f74206265207a65726f");
    r.numerator = num;
    assembly  { { if 0x10000000001 { } } }
    bytes32 v_69452 = keccak256(abi.encodePacked(msg.sender));
    r.denominator = denom;
  }

  constructor () {
    r.numerator = -1;
    r.denominator = 2;
  }

}

trace = w3.manager.request_blocking('debug_traceTransaction', [tx_hash, {'tracer':'prestateTracer','tracerConfig': {'diffMode': True}}])

Result:

AttributeDict({'post': AttributeDict({'0x0000000000000000000000000000000000000000': AttributeDict({'balance': '0x355dacaa5c6e'}), '0x5c9776deac45c8b416239604cd8850d5dc81d3fb': AttributeDict({'storage': AttributeDict({'0x0000000000000000000000000000000000000000000000000000000000000001': '0xf7d9c0469c411e6b7d7863011ce7f3f258685e4ce99f5467f28c3598787722b5'})}), '0xbe931d46286d4e27217d57d1a4672b4d536e46fd': AttributeDict({'balance': '0xfffffffffffffffffffffffffffffffffffffffffffffffffffe84c17977809d', 'nonce': 3})}), 'pre': AttributeDict({'0x0000000000000000000000000000000000000000': AttributeDict({'balance': '0x2f9aa6ccc4bb'}), '0x5c9776deac45c8b416239604cd8850d5dc81d3fb': AttributeDict({'balance': '0x0', 'code': '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', 'nonce': 1, 'storage': AttributeDict({'0x0000000000000000000000000000000000000000000000000000000000000000': '0xb412fa0861bb1532171e2f7e6d88df75e8bb79d4ba10674f506b1d13a2d973b0', '0x0000000000000000000000000000000000000000000000000000000000000001': '0x0000000000000000000000000000000000000000000000000000000000000036'})}), '0xbe931d46286d4e27217d57d1a4672b4d536e46fd': AttributeDict({'balance': '0xfffffffffffffffffffffffffffffffffffffffffffffffffffe9c276179cd9e', 'nonce': 2})})})

[lightclient]

Seems empty values are explicitly removed:

go-ethereum/eth/tracers/native/prestate.go

Lines 234 to 237 in e3d61e6

	// don't include the empty slot
	if val == (common.Hash{}) {
	delete(t.pre[addr].Storage, key)
	}

would ask @s1na, @jsvisa for more context.

Looks to always have been this way: #25422

[jsvisa]

Yeah, the cleared post storage were not included:

go-ethereum/eth/tracers/native/prestate.go

Lines 245 to 247 in e3d61e6

	if newVal != (common.Hash{}) {
	postAccount.Storage[key] = newVal
	}

[lightclient]

Honestly I also stumbled across this a few weeks ago. What was the reasoning for not just including a simple diff w/o removing zero values ? Is it okay to remove these clauses?