Error in compiling Rust into webassembly using emscripten on Windows

1
votes

I just tried to compile Rust example project into webassembly using emscripten on Windows, but it causes error. How can I fix it?

What I did:

  1. Install emscripten
>git clone https://github.com/emscripten-core/emsdk.git
>cd emsdk
>git pull
>emsdk install latest
>emsdk activate latest
>emsdk_env.bat
  1. Install rustup Download rustup-init.exe from https://www.rust-lang.org/ja/tools/install and run it
  2. Install wasm32 target by rustup
>rustup target add wasm32-unknown-emscripten
  1. Create example project
>cargo new --bin web_assembly
>cd web_assembly
  1. Try to compile, but error occurs
>cargo build --target wasm32-unknown-emscripten
   Compiling web_assembly v0.1.0 (F:\github\rusttest\web_assembly)
error: linking with `emcc.bat` failed: exit code: 1
  |
  = note: "cmd" "/c" "emcc.bat" "-s" "DISABLE_EXCEPTION_CATCHING=0" "-L" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib" "-L" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\self-contained" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.0.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.1.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.2.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.3.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.4.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.5.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.6.rcgu.o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.web_assembly.egwz9uoo-cgu.7.rcgu.o" "-o" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.js" "-s" "EXPORTED_FUNCTIONS=[\"_main\",\"_rust_eh_personality\"]" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps\\web_assembly.3a2jxscq1lvbzwaf.rcgu.o" "-O0" "--memory-init-file" "0" "-g4" "-s" "DEFAULT_LIBRARY_FUNCS_TO_INCLUDE=[]" "-L" "F:\\github\\rusttest\\web_assembly\\target\\wasm32-unknown-emscripten\\debug\\deps" "-L" "F:\\github\\rusttest\\web_assembly\\target\\debug\\deps" "-L" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libstd-28368703ab79076a.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libpanic_unwind-c6cbccdff18b55f7.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\librustc_demangle-a5ffc5310c14c91c.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libhashbrown-08c349e57dac68c0.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\librustc_std_workspace_alloc-ce3363c7b27912b6.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libunwind-686deac84d1c117a.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libcfg_if-1aefc0615f4a87c4.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\liblibc-35a51890c8428321.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\liballoc-d41456f5d5a426f6.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\librustc_std_workspace_core-2a7cc4e4deb2c4e8.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libcore-997b7450818c8186.rlib" "C:\\Users\\Username\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libcompiler_builtins-68f9d21fef2c27f2.rlib" "-l" "c" "-s" "ERROR_ON_UNDEFINED_SYMBOLS=1" "-s" "ASSERTIONS=1" "-s" "ABORTING_MALLOC=0" "-Wl,--fatal-warnings"
  = note: shared:INFO: (Emscripten: Running sanity checks)
          emcc: warning: please replace -g4 with -gsource-map [-Wdeprecated]
          error: undefined symbol: __gxx_personality_v0 (referenced by top-level compiled C/C++ code)
          warning: Link with `-s LLD_REPORT_UNDEFINED` to get more information on undefined symbols
          warning: To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`
          warning: ___gxx_personality_v0 may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
          Error: Aborting compilation due to previous errors
          emcc: error: 'F:/github/emsdk/node/14.15.5_64bit/bin/node.exe F:\github\emsdk\upstream\emscripten\src\compiler.js C:\Users\Username\AppData\Local\Temp\tmpang8muuo.txt' failed (1)


error: aborting due to previous error

error: could not compile `web_assembly`

To learn more, run the command again with --verbose.

Versions of tools:

>emcc.bat --version
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 2.0.20-git (8ed0f4fee2abd04923c2fd2bf44835169ce2ac2e)
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

>rustup --version
rustup 1.24.1 (a01bd6b0d 2021-04-27)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.52.1 (9bc8c42bb 2021-05-09)`
2
windowsrustwebassemblyemscriptenrustup
If Emscripten is not a hard requirement, you might have a better experience with the wasm32-unknown-unknown target. I am not even sure if the Emscripten target is as well maintained these days. The Rust and WebAssembly book provides a tutorial and useful resources. - E_net4 the commentary remover
Thank you, it works! Maybe the article I referenced was bit old. But how should I close this ticket with your comment? Would you please make answer? - kochizufan

2 Answers

2
votes

If you don't strictly require Emscripten, you should use Rust's custom WASM support, which is available through the wasm32-unknown-unknown as this is where most of Rust-related WASM development happens.

If you want an example of how to use this target, check out the Rust WASM book.

4
votes

Emscripten uses tip-of-tree LLVM, which may be incompatible with the more stable version of LLVM used by Rust. That means that you have to use a particular version of Emscripten with an LLVM that closely matches Rust's version of LLVM rather than using latest.

The version of Emscripten that most closely matches Rust's LLVM since Rust 52 is Emscripten 2.0.13, so I would try using that.

The best resource documenting and tracking the best version of Emscripten to use is https://blog.therocode.net/2020/10/a-guide-to-rust-sdl2-emscripten, although it hasn't been updated for Rust 52+.