Re: Benefit of the effect system?

[federico3]

I wish the effect system could be used to implement sandboxing.

The stdlib procs that run system calls could be tagged accordingly, and the 
application's "main" could then set up a sandbox at runtime to allow only the 
required system calls.

Re: Benefit of the effect system?

[Yardanico]

Well, then cast should also have a special effect because it can be used to 
strip off any pragmas

Re: Benefit of the effect system?

[Yardanico]

{.pragma: raisesssz, raises: [Defect, MalformedSszError, 
SszSizeMismatchError].}


Run

Makes a new pragma called `raisesssz`, which, when used, will imply `raises: 
[Defect, MalformedSszError, SszSizeMismatchError]`

Re: Benefit of the effect system?

[snej]

What does the `{.raises:[...].}` pragma at the top of a source file do, as in 
your ssz_serialization.nim? The manual only describes it as a proc annotation.

Re: Benefit of the effect system?

[mratsim]

We use it in our code to:

  * Enforce noSideEffect (i.e. no access to globals, including stdin/stdout).
  * Enforce handling of recoverable exceptions and make sure all kinds of 
exceptions that can be thrown in inner function calls are accounted for or 
handled or considered irrecoverable:
* Serialization 
[https://github.com/status-im/nim-beacon-chain/blob/db92c2f25/beacon_chain/ssz/ssz_serialization.nim#L4](https://github.com/status-im/nim-beacon-chain/blob/db92c2f25/beacon_chain/ssz/ssz_serialization.nim#L4)
* Fuzzing 
[https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/nfuzz/libnfuzz.nim#L37](https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/nfuzz/libnfuzz.nim#L37)
  * You can force `{.noSideEffect.}` and `{.gcsafe.}` with a block
* 
[https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/beacon_chain/fork_choice/fork_choice.nim#L161-L166](https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/beacon_chain/fork_choice/fork_choice.nim#L161-L166)