Stream: wit-bindgen

Topic: module requires an import interface named env

benwis (Feb 24 2024 at 21:46):

I've tried using both cargo component and manual wit-bindgen, but both give me an error error: module requires an import interface named env`` converting a preview1 wasm module to a preview2 wasm component , and I can't find a reference to it in the example

Joel Dice (Feb 24 2024 at 22:26):

You can use e.g. wasm-tools print to see what functions the module is importing from env, which might point to what's wrong.

benwis (Feb 24 2024 at 22:29):

Interesting, I guess it's these:

  (import "env" "_Znwm" (func $_Znwm (;0;) (type 4)))
  (import "env" "_ZdlPv" (func $_ZdlPv (;1;) (type 0)))
  (import "env" "__cxa_allocate_exception" (func $__cxa_allocate_exception (;2;) (type 4)))
  (import "env" "_ZNSt12length_errorD1Ev" (func $_ZNSt12length_errorD1Ev (;3;) (type 4)))
  (import "env" "__cxa_throw" (func $__cxa_throw (;4;) (type 6)))
  (import "env" "_ZNSt20bad_array_new_lengthD1Ev" (func $_ZNSt20bad_array_new_lengthD1Ev (;5;) (type 4)))
  (import "env" "_ZNSt20bad_array_new_lengthC1Ev" (func $_ZNSt20bad_array_new_lengthC1Ev (;6;) (type 4)))
  (import "env" "_ZnwmSt11align_val_t" (func $_ZnwmSt11align_val_t (;20;) (type 3)))
  (import "env" "_ZdlPvSt11align_val_t" (func $_ZdlPvSt11align_val_t (;21;) (type 2)))

Dan Gohman (Feb 24 2024 at 22:32):

Did you by chance link C++ code using the clang command? If so, you may need to link with the clang++ command.

benwis (Feb 24 2024 at 22:33):

Yeah, this was the build command

RUSTFLAGS='-L /opt/wasi-sdk-21.0/share/wasi-sysroot/lib/wasm32-wasi' CXXSTDLIB=c++ CC=/opt/wasi-sdk-21.0/bin/clang CXX=/opt/wasi-sdk-21.0/bin/clang  cargo component build

Dan Gohman (Feb 24 2024 at 22:34):

Yeah; try changing the clang at the end of the CXX to clang++

Joel Dice (Feb 24 2024 at 22:35):

Context: this rust library pulls in a wrapper crate for tree-sitter, which is written (partly) in C++

benwis (Feb 24 2024 at 22:37):

This gives the same error and the same env lines

 RUSTFLAGS='-L /opt/wasi-sdk-21.0/share/wasi-sysroot/lib/wasm32-wasi' CXXSTDLIB=c++ CC=/opt/wasi-sdk-21.0/bin/clang CXX=/opt/wasi-sdk-21.0/bin/clang++  cargo component build

Joel Dice (Feb 24 2024 at 22:46):

IIRC, the linker was rust-lld

benwis (Feb 24 2024 at 22:47):

I did get that error at one point that mentioned rust-lld
This is the repo if anyone wants to try: https://github.com/benwis/femark/tree/wasi
Running on latest Rust stable on Arch Linux

benwis (Feb 24 2024 at 23:14):

Joel Dice said:

IIRC, the linker was rust-lld

I could tell cargo to try using an alternate linker, is the lld in the same folder the recommended one?

Dan Gohman (Feb 24 2024 at 23:33):

I'd guess rust-lld is fine, but what's needed is to link in the C++ standard library. You may need to add something like -lc++ -lc++abi to the link line..

benwis (Feb 25 2024 at 01:52):

Dan Gohman said:

I'd guess rust-lld is fine, but what's needed is to link in the C++ standard library. You may need to add something like -lc++ -lc++abi to the link line..

For a C build noob, where would I add that?

benwis (Feb 25 2024 at 03:15):

Ok I tried adding it to RUSTFLAGS like so

RUSTFLAGS='-L /opt/wasi-sdk-21.0/share/wasi-sysroot/lib/wasm32-wasi -lstatic=c++ -lstatic=c++abi' CXXSTDLIB=c++ CC=/opt/wasi-sdk-21.0/bin/clang CXX=/opt/wasi-sdk-21.0/bin/clang++  cargo component build

it seems to throw the same error, I'll play with this a bit. I don't understand where the env interface comes from and what controls what goes into it

benwis (Feb 25 2024 at 04:08):

A thought occurs to me that this might not be a cargo issue, since it successfully builds

   Compiling wit-parser v0.200.0
   Compiling wasm-metadata v0.200.0
   Compiling tree-sitter-highlight v0.20.1
   Compiling wit-bindgen-core v0.19.1
   Compiling wit-component v0.200.0
   Compiling femark v0.1.3 (/celCluster/projects/femark)
    Finished dev [unoptimized + debuginfo] target(s) in 10.67s
    Creating component /celCluster/projects/femark/target/wasm32-wasi/debug/femark.wasm
error: module requires an import interface named `env`

femark on  wasi [$!?] is 📦 v0.1.3 via 🦀 v1.76.0 took 10s

and it's only the conversion to preview2 that's failing

benwis (Feb 25 2024 at 06:10):

Fixed it, turns out I needed to set CXXFLAGS=-fno-exceptions and that cleared it right up

Last updated: Dec 23 2024 at 13:07 UTC