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FEVM: document the differences in the Filecoin BLOCKHASH instruction #2378

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Apr 2, 2025
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FEVM: document the differences in the Filecoin BLOCKHASH instruction #2378

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7 changes: 7 additions & 0 deletions smart-contracts/filecoin-evm-runtime/difference-with-ethereum.md
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Expand Up @@ -36,6 +36,13 @@ Filecoin EVM runtime emulates EVM self-destruct behavior but isn’t able to ent

The `CALLCODE` opcode has not been implemented. Use the newer `DELEGATECALL` opcode.

## BLOCKHASH

Ethereum has one block at every height while Filecoin can have none, one, or many (usually around 4-5). This means that the `BLOCKHASH` instruction behaves a bit differently in the Filecoin EVM:

- Because there can be multiple blocks at any given height, `BLOCKHASH` returns the hash of all the concatenation of the CIDs of all the blocks at the requested height.
- Because there can be no blocks at any given height, if `BLOCKHASH` is called on a height with _no blocks_, it returns the `BLOCKHASH` of the first preceding height with blocks.

## Bare-value sends

In Ethereum, `SELFDESTRUCT` is the only way to send funds to a smart contract without giving the target smart contract a chance to execute code.
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