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Swift array count: expected return to have type code 'q', but found 'Q' #566

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1tgr opened this issue Jan 20, 2024 · 3 comments · Fixed by #567
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Swift array count: expected return to have type code 'q', but found 'Q' #566

1tgr opened this issue Jan 20, 2024 · 3 comments · Fixed by #567
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A-objc2 Affects the `objc2`, `objc-sys` and/or `objc2-encode` crates bug Something isn't working

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@1tgr
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1tgr commented Jan 20, 2024 •
edited

I'm exposing this Rust function to Swift:

#[no_mangle]
pub extern "C" fn time_series_eval(
    exprs: *mut NSArray<NSString>,
    error: &mut *mut NSError,
) -> *mut NSDictionary<NSString, NSArray> {
    let exprs = exprs.as_ref().unwrap().iter();
    // do something with exprs
}

I call it like this from the Swift side:

var error: NSError?
let result = time_series_eval(["abc"], &error)

But the Rust panics:

~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/icrate-0.1.0/src/generated/Foundation/NSEnumerator.rs:6:1:
invalid message send to -[Swift.__SwiftDeferredNSArray countByEnumeratingWithState:objects:count:]: expected return to have type code 'q', but found 'Q'

I think this is telling me that Swift arrays and objc2's arrays don't agree on signed vs unsigned?
This was referenced Jan 21, 2024
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@madsmtm madsmtm added bug Something isn't working A-objc2 Affects the `objc2`, `objc-sys` and/or `objc2-encode` crates labels Jan 21, 2024
@madsmtm
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madsmtm commented Jan 21, 2024 •
edited

I think this is telling me that Swift arrays and objc2's arrays don't agree on signed vs unsigned?

Rather, Swift is lazy and uses Int instead of the more correct type UInt here; the difference doesn't really matter to them, as arrays likely won't be able to ever get so large that it matters.

I've opened #567 to fix this, although I'm a bit unsure what the right approach is. In the meantime the easiest fix for you is probably to do one of:

  • Patch in Ignore signed-ness in encoding #567 locally (using the patch.crates-io Cargo.toml key).
  • Re-implement the iteration yourself using objectAtIndex:.
  • Disable debug assertions.

@1tgr
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1tgr commented Jan 22, 2024 •
edited

Thanks for the quick response. I took a local copy of the repo and did a quick hack equivalent to #567 that avoided the problem and I'll try taking a Git dependency on #567 for now.

@madsmtm
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madsmtm commented May 20, 2024

I went with a Cargo feature flag called relax-sign-encoding, you should be able to use that instead once I release objc2 v0.5.2

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A-objc2 Affects the `objc2`, `objc-sys` and/or `objc2-encode` crates bug Something isn't working
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Ignore signed-ness in encoding madsmtm/objc2
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