deserializing a slotmap compiled to .wasm causes error.

[rebo]

Slotmap works just fine in web assembly with just one exception. It appears that deserialization with serde does not work. (Serialization works just fine).

I really have no idea if this is a problem with Slotmap, Serde, or wasm_bindgen it really is above my head.

Anyway. this code ::

        let mut sm: SlotMap<PlayerKey, u32> = SlotMap::with_key();

        sm.insert(3);

        let j = serde_json::to_string(&sm).unwrap(); // serialization works fine

        print!("{}",j );

        let sm2 : SlotMap<PlayerKey, u32> = serde_json::from_str(&j).unwrap();

causes this error only in a wasm environment ::

`panicked at 'attempt to shift left with overflow', /Users/rebo/.cargo/registry/src/github.com-1ecc6299db9ec823/slotmap-0.3.0/src/normal.rs:1068:31

Stack:

Error at Module.wbg_new_59cb74e423758ede (webpack-internal:///./crate/pkg/index.js:547:21) at wbg_new_59cb74e423758ede (http://localhost:8000/app.js?56a04bc9da773126182b:801:101) at console_error_panic_hook::Error::new::hf9155aeb30e0df7c (wasm-function[11765]:22) at console_error_panic_hook::hook_impl::h19b17601d076c52f (wasm-function[2120]:100) at console_error_panic_hook::hook::hd8298b7121f5bbfe (wasm-function[12932]:38) at core::ops::function::Fn::call::hced78bec1b5a708c (wasm-function[11784]:45) at std::panicking::rust_panic_with_hook::hefb6d16d56fedd94 (wasm-function[3093]:265) at std::panicking::continue_panic_fmt::ha605a3bfcbd9f700 (wasm-function[6701]:116) at rust_begin_unwind (wasm-function[14788]:3) at core::panicking::panic_fmt::hc16a7652262fbed2 (wasm-function[12041]:70)`

[orlp]

Does WebAssembly have a 32-bit usize? Now there's definitely an issue in my code that I compute 2^32 - 1 with (1 << 32) - 1 as this won't work on 32-bit systems.

However... how did this compile? This should give a compile-time error: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=f233a1f5f93c82a748d1f0d8da58e34c .

[orlp]

This issue should be fixed in the latest commit. It's going to take a bit (probably at least a couple days to a week) for me to publish 0.4, I have some other changes I'd like to make for that.

[rebo]

Thank you very much for looking at this, unfortunately the example above still panics for me on deserialize when using the latest commit on master.

I have created a small sample app that demonstrates this phenomena.

https://github.com/rebo/sm_issue

[orlp]

What is the panic traceback?

[rebo]

It's a little bit different:

RuntimeError: unreachable
    at __rust_start_panic (wasm-function[1114]:1)
    at rust_panic (wasm-function[1004]:31)
    at std::panicking::rust_panic_with_hook::hefb6d16d56fedd94 (wasm-function[246]:304)
    at std::panicking::continue_panic_fmt::ha605a3bfcbd9f700 (wasm-function[533]:116)
    at rust_begin_unwind (wasm-function[1103]:3)
    at core::panicking::panic_fmt::hc16a7652262fbed2 (wasm-function[843]:70)
    at core::panicking::panic::h1f84f7eb49aeaec9 (wasm-function[627]:100)
    at slotmap::normal::serialize::<impl serde::de::Deserialize for slotmap::normal::SlotMap<K,V>>::deserialize::hd239fa69a2c00838 (wasm-function[30]:1967)
    at serde_json::de::from_trait::hc4dda8f146982609 (wasm-function[54]:121)
    at serde_json::de::from_str::h2a6f0f9869081e1d (wasm-function[485]:93)

[orlp]

Alright I tracked it down, it was the exact same issue, just in two other places. I wasn't using a local repository when doing my first fix, so I used Github search in the repo to see if there were any other instances. Unfortunately these instances never showed up with that search. Could you try again with the latest commit?

[rebo]

Again thanks for getting to this so quickly. Looks like we are not quite there yet, here is the latest trace from a new panic than the last one (but similar to the first one lol).

index.js?91f7:408 panicked at 'attempt to shift left with overflow', /Users/rebo/Coding/Projects/Rust/stiff/slotmap/src/normal.rs:1090:31

Stack:

Error
    at Module.__wbg_new_59cb74e423758ede (webpack-internal:///./crate/pkg/index.js:547:21)
    at __wbg_new_59cb74e423758ede (http://localhost:8000/app.js?d0084421dcdfb4bedfd4:801:101)
    at console_error_panic_hook::Error::new::hf9155aeb30e0df7c (wasm-function[11764]:22)
    at console_error_panic_hook::hook_impl::h19b17601d076c52f (wasm-function[2120]:100)
    at console_error_panic_hook::hook::hd8298b7121f5bbfe (wasm-function[12931]:38)
    at core::ops::function::Fn::call::hced78bec1b5a708c (wasm-function[11783]:45)
    at std::panicking::rust_panic_with_hook::hefb6d16d56fedd94 (wasm-function[3092]:265)
    at std::panicking::continue_panic_fmt::ha605a3bfcbd9f700 (wasm-function[6701]:116)
    at rust_begin_unwind (wasm-function[14785]:3)
    at core::panicking::panic_fmt::hc16a7652262fbed2 (wasm-function[12040]:70)

[nabijaczleweli]

(are you sure you're on the latest commit?)

[orlp]

@rebo I believe you do not have the latest version as the line number in that panic message is a line I fixed.

[rebo]

Hi Orlp and nabijaczleweli ,

I am happy to report this works fine now. Tested under slotmap 0.4 and latest nightly.

Many thanks for fixing it so quickly.