EVM: simplify and fix evm storage #831
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There isn't really a good reason to be tracking storage status of an item unless you are doing analysis of the values, though at that point you could view the blockstore changes directly and build tooling to analyze at that layer (like we currently do with our memory analysis graphs). 👍
1. The EVM doesn't distinguish between "exists" and "doesn't exist". 2. There was some interesting dead code. 3. Only mark the state-tree dirty if something has changed.
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| let opt_value = if value == U256::zero() { None } else { Some(value) }; | ||
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| system.set_storage(location, opt_value)?; | ||
| system.set_storage(state.stack.pop(), state.stack.pop())?; |
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Wait, this is potential undefined behavior with the pops.
Does rust mandate left to right evaluation order for args?
In any othe language you've shot yourself in the foot here.
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left -> right, in -> out. Yes.
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uhm ok, interesting.
Can we still either pop first to named or add a comment regardless?
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Sure, we can pop first. I agree that it does make the pop order clearer.
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left to right is how it is evaluated https://doc.rust-lang.org/reference/expressions.html#evaluation-order-of-operands
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I have to say, it is highly unusual of high perf languages to do that.
The compiler is allowed to go bersek here, ocaml does right to left, some C compilers do whatever works faster situationally, and in scheme you are expelled if you assume evaluation order :)
| None => U256::zero(), | ||
| }; | ||
| state.stack.push(value); | ||
| state.stack.push(system.get_storage(location)?); |
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error? Doesnt evm zero for everything?
Ot is it internal now?
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This is a fatal "something is really broken" error (same as before).
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Ok, do we have a test for this?
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No? This is a "the HAMT is corrupted" error. I.e., there's a bug.
| Ok(self | ||
| .slots | ||
| .get(&key) | ||
| .map_err(|e| StatusCode::InternalError(e.to_string()))? |
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get of something not existing is just zero.
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Yes. In the EVM, all storage "exists", it's just all zeros.
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See the fixed test below.
Well, there was a test. It was just wrong. |
Codecov Report
Additional details and impacted files@@ Coverage Diff @@
## next #831 +/- ##
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- Coverage 87.50% 87.49% -0.01%
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Files 125 125
Lines 22649 22634 -15
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- Hits 19818 19803 -15
Misses 2831 2831
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fixes the second half of filecoin-project/ref-fvm#912