Description
Currently UInt
wraps on overflow. Please, make it panic on overflow if cfg(overflow_checks)
is enabled, i. e. exactly same thing rustc does with standard numbers. Here is why.
First and foremost, ruint
is used mainly for representing monetary values. Wrapping behavior is unnatural for monetary values. So, UInt
should panic on overflow. But still some users may want to skip checks for speed reasons. So, we should provide way to configure behavior. The most natural thing to do is to make UInt
panic when standard numbers panic and wrap when standard types wrap. So, we should use cfg(overflow_checks)
.
Of course, this is breaking change, so it should be done in 2.0.0.
I use alloy
for managing my cryptocurrency, i. e. for transferring it around. Unnoticed overflows may cause loss of money, I absolutely don't want this. alloy
directly uses ruint
's UInt
. So, I plan to create my wrapper around U256
, which will panic on overflow. And I also will use clippy::arithmetic_side_effects
to make sure that I will not use arithmetic directly on ruint
/alloy
's U256
. But ideally this should be fixed in ruint
itself
Activity
u59149403 commentedon Dec 15, 2024
See rust-lang/rust#91130 and rust-lang/rust#111466
prestwich commentedon Dec 16, 2024
ruint
is intended to support the modular arithmetic required for cryptographic applications. Adding overflow checks based oncfg(overflow_checks)
would mean that consumers of the library could inadvertently breakruint
when used as a subdep. E.g. if you used a hypotheticalruint-ecdsa
, it would be broken if you enabledcfg(overflow_checks)
for your projectIs there a reason that using the
checked_*
API is not sufficient for your project?u59149403 commentedon Dec 17, 2024
As I said this requires me to depend on special clippy lints. But okay, this is your project, so feel free to close this issue if you want
prestwich commentedon Dec 17, 2024
when writing consensus code, I would strongly recommend always using checked arithmetic, even with primitive number types, rather than panicking. Accidentally leaving reachable panics in consensus code can lead to network-wide DOS
for now, closing this as
wontfix
Yen commentedon Feb 16, 2025
Would it be possible to reassess this as I don't think it's the correct behaviour. I fully agree that people shouldn't be relying on behaviour like this to catch errors, but I was running into issues with overflows and had a hard time debugging the issue as the assumption was that the behaviour here would be the same as the standard rust types. I think the decision of the way to do things should not made here as it has already been decided by the rust team with the standard types. I would argue that replicating the default rust behaviour is far more important than trying to enforce good practice with a different behaviour in this library that nobody will know about unless they are hit by this case wile debugging and end up on this issue like I did.
I think the above comment for using checked arithmetic is a very reasonable thing to say as an argument against the rust standard types behaviour, but here it's far more important to have consistent behaviour with those types and to panic in debug.
Yen commentedon Feb 16, 2025
For reference, the issue I had debugging was that I was debugging under the rust assumption that in debug mode, overflows will panic. It took a long time checking many other parts of the code before I realised that it was overflowing, and it was the different behaviour in this library that broke that assumption.