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Introducing Transience, a library for safely using transient storage in Solidity (without assembly).

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Introducing Transience, a library for safely using transient storage in Solidity (without assembly).

https://github.com/ethereum-optimism/transience

What does the library offer?
- It allows writing and reading transient storage without assembly/Yul
- It prevents reentrant calls from overwriting transient storage

Use modifier 𝘳𝘦𝘦𝘯𝘵𝘳𝘢𝘯𝘵𝘈𝘸𝘢𝘳𝘦 to prevent a reentrant call from overwriting a slot in transient storage. This is possible because the modifier automatically increments and decrements the call depth when entering and exiting the function.

Transience was developed for the interop contracts of the OP Stack/Optimism, specifically for CrossL2Inbox, where it's used for storing the identifier of a cross-chain message during its execution.

Transience was developed for the interop contracts of the OP Stack/Optimism, specifically for CrossL2Inbox, where it's used for storing the identifier of a cross-chain message during its execution.

https://github.com/ethereum-optimism/optimism/blob/3aeb6bdd3efe798713098f890359513eaaa91522/packages/contracts-bedrock/src/L2/CrossL2Inbox.sol

Check out the code!

h/t @philogy and @jtriley, whose libraries served as inspiration :)

Check out the code!

h/t @philogy and @jtriley, whose libraries served as inspiration :)

https://github.com/ethereum-optimism/transience

You get these methods:
- get(bytes32 _slot) for retrieving a transient value
- set(bytes32 _slot, uint256 _value) for setting a transient value

_slot and the current call depth are used to determine a unique location in transient storage.