where can i find the impl code of `canonical_abi_realloc` for assemblyscript?

[xiaosongfu]

I use this tool to generate the binding for wasmtime, and now i want to compile assemblyscript code to wasm module and run it in wasmtime, i need canonical_abi_realloc code for assemblyscript.

[esoterra]

Based on what you've said, it sounds like you've used a host bindings generator (e.g. wasmtime-py or wasmtime) and are now trying to compile an AssemblyScript module that you can use with them. Is that correct?

For languages with guest bindings support, like C or Rust, you can just run the generator and it will provide everything your module needs. However, wit-bindgen doesn't have AssemblyScript guest bindings support, so you would have to implement the Canonical ABI code yourself in AssemblyScript.

If you want more info on canonical_abi_realloc, check out these links.

• Canonical ABI Explainer
• canonical_abi_realloc C implementation
• Original description of canonical_abi_realloc

[willemneal]

To add to this there is a realloc method implemented in AS's stdlib, however, it has a different signature. AS's allocator will be able to look up the original size and alignment, so you can drop those two when calling the inner function.

[xiaosongfu]

@Kylebrown9 yes, your understanding is right.

[xiaosongfu]

@willemneal i have tried it, this is my code:

export function canonical_abi_realloc(old_ptr: u8, old_len: usize, align: usize, new_len: usize): usize {
    return heap.realloc(old_ptr, new_len);
}

but it does not work, there is something wrong? thank you! and i need your help

[willemneal]

What errors are you getting?

[xiaosongfu]

@willemneal thanks

Error: wasm trap: wasm `unreachable` instruction executed
wasm backtrace:
    0:  0x69b - <unknown>!<wasm function 7>
    1:  0x76e - <unknown>!<wasm function 8>


Stack backtrace:
   0: std::backtrace_rs::backtrace::libunwind::trace
             at /rustc/082e4ca49770ebc9cb0ee616f3726a67471be8cb/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at /rustc/082e4ca49770ebc9cb0ee616f3726a67471be8cb/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2: std::backtrace::Backtrace::create
             at /rustc/082e4ca49770ebc9cb0ee616f3726a67471be8cb/library/std/src/backtrace.rs:328:13
   3: std::backtrace::Backtrace::capture
             at /rustc/082e4ca49770ebc9cb0ee616f3726a67471be8cb/library/std/src/backtrace.rs:296:9
   4: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /Users/xiaosongfu/.cargo/registry/src/rsproxy.cn-8f6827c7555bfaf8/anyhow-1.0.57/src/error.rs:533:25
   5: <core::result::Result<T,F> as core::ops::try_trait::FromResidual<core::result::Result<core::convert::Infallible,E>>>::from_residual
             at /rustc/082e4ca49770ebc9cb0ee616f3726a67471be8cb/library/core/src/result.rs:2105:27
   6: run::main
             at ./run/src/main.rs:39:5

[xiaosongfu]

Is there anything else need I provide? @willemneal

[willemneal]

A link to your repo would be the best. Hard to tell exactly where the unreachable is occurring.

[alexcrichton]

I believe that the original question here was somewhat answered and while there may be more issues remaining it might be best to raise this as a question on Zulip or open a new issue, so closing.