RUNTIME_DISPATCH_ERROR: Reentrancy detected error

[ariesgun]

Discord user ID

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Describe your question in detail.

I have implemented a dispatchable_fungible_asset based on https://github.com/aptos-labs/aptos-core/blob/main/aptos-move/move-examples/fungible_asset/fa_coin/sources/FACoin.move.

In my unit test:

let fa = primary_fungible_store::withdraw(receiver, metadata, 5);
primary_fungible_store::deposit(to_address, fa);

I got this error.

According to the documentation, I should be able to use primary_fungible_store to deposit or withdraw without changing anything.
What did I miss here?

What error, if any, are you getting?

No response

What have you tried or looked at? Or how can we reproduce the error?

No response

Which operating system are you using?

Windows

Which SDK or tool are you using? (if any)

TypeScript SDK

Describe your environment or tooling in detail

No response

[runtian-zhou]

Thanks for the question! The important thing here is in the dispatch function hook (the withdraw/deposit function you implemented), make sure it will not call into primary_fungible_store. The error means that during execution there is a cycle on the call stack (such as module A calls module B, and module B calls back into module A). Lemme know if you have more questions!

[ariesgun]

I see.. Then the first paragraph in https://aptos.dev/en/build/smart-contracts/fungible-asset#interacting-with-dispatchable-fungible-asset is not accurate then. Is it possible for users to use fungible_asset::deposit() or fungibe_asset::withdraw() to transfer the dispatchable fungible asset?

[kshitjee]

@runtian-zhou perhaps we can make this clearer given the complexity.

@ariesgun, the issue is possibly that your hooks call into primary_fungible_store.move, please let me know if this is not the case.

the distinction lies in the fact that:

a) contracts interacting with an asset (say FAcoin) can continue to call into primary_fungible_store::withdraw/deposit, since there is no risk of reentrancy.

i.e. pfs::withdraw -> dfa::withdraw -> fa_coin::withdraw -> fa::withdraw_with_ref, so we're good.

b) contracts that define their asset and hook (so you, the person deploying the FACoin module), can't call into ANY function in pfs WITHIN your hook logic. this causes a potential reentrancy, which you're experiencing.

i.e. pfs::withdraw -> dfa::withdraw -> fa_coin::withdraw -> pfs::withdraw (cycle on call stack) (can be any other function in pfs too, that is not inlined).

basically, its the responsibility of the developer implementing the hooks to prevent cases of cyclical dependencies, not the protocols already interacting with the asset (using primary stores).

[kshitjee]

also maybe check this discussion out for more context: #296

[ariesgun]

Thanks for the detailed explanation. I figured out what caused the reentrancy error.

[kshitjee]

@ariesgun out of curiosity, what was the issue?

[ariesgun]

I called the primary_fungible_store::deposit/withdraw in the unit test which is located in the same file as the implementation of dispatchable withdraw/deposit functions. This's what caused the reentrancy error.
When I called it from a different module, it worked just fine.

[runtian-zhou]

No. There is a pretty complex reason for this that. If you are interested in that you should probably look at the aip. The tl;dr is fungible_asset::deposit() only does transfer for non dispatchable assets. You can use primary_fungible_store::transfer to transfer both dispatchable and non dispatchable assets.

[runtian-zhou]

Then the first paragraph in https://aptos.dev/en/build/smart-contracts/fungible-asset#interacting-with-dispatchable-fungible-asset is not accurate then

Looking at the doc it does seem accurate?

It does suggest the following:

For users using secondary FungibleStore to interact with assets, use dispatchable_fungible_asset::withdraw/deposit instead of fungible_asset::withdraw/deposit to handle assets with registered hooks.