I can't make a web build for release

[SoftHardcore]

I tried compiling the Rust library for the dodge-the-creeps project to obtain the '.wasm' file for both debug and release versions. To do this, I followed the steps from the Export to Web documentation.

I downloaded emscripten and executed all the necessary commands from the documentation:

rustup toolchain install nightly
rustup component add rust-src --toolchain nightly
rustup target add wasm32-unknown-emscripten --toolchain nightly

./emsdk install 3.1.62
./emsdk activate 3.1.62
source ./emsdk_env.sh # btw, the documentation mentions an outdated command `source ./emsdk.sh`

Then, I tried to build the release version:

cargo +nightly build --release -Zbuild-std --features godot/experimental-wasm,godot/lazy-function-tables --target wasm32-unknown-emscripten

And if for the debug build I had a successful result, then an attempt to compile a build for release with the --release flag at the end of the compilation gave an error:

   ...
   Compiling rand v0.8.5
   Compiling godot v0.2.4 (https://github.com/godot-rust/gdext.git#b0be794c)
   Compiling dodge-the-creeps v0.1.0 (/home/user/projects/ProjectsGodot/dodge-the-creeps/rust)
warning: unstable feature specified for `-Ctarget-feature`: `atomics`
  |
  = note: this feature is not stably supported; its behavior can change in the future

error: linking with `emcc` failed: exit status: 1
  |
  = note:  "emcc" "-s" "EXPORTED_FUNCTIONS=[\"___godot_rust_registrant_1025202362_1350490027\",\"___godot_rust_registrant_1101513929_1801979802\",\"___godot_rust_registrant_1365180540_1540383426\",\"___godot_rust_registrant_1681692777_1714636915\",\"___godot_rust_registrant_1804289383_846930886\",\"___godot_rust_registrant_1957747793_424238335\",\"___godot_rust_registrant_2044897763_1967513926\",\"___godot_rust_registrant_2145174067_468703135\",\"___godot_rust_registrant_278722862_233665123\",\"___godot_rust_registrant_294702567_1726956429\",\"___godot_rust_registrant_304089172_1303455736\",\"___godot_rust_registrant_336465782_861021530\",\"___godot_rust_registrant_35005211_521595368\",\"___godot_rust_registrant_596516649_1189641421\",\"___godot_rust_registrant_719885386_1649760492\",\"___godot_rust_registrant_783368690_1102520059\",\"_gdext_rust_init\"]" "<17 object files omitted>" "/home/user/projects/ProjectsGodot/dodge-the-creeps/rust/target/wasm32-unknown-emscripten/release/deps/{librand-5091c1d6dfbe5787.rlib,librand_chacha-851518d53be850a0.rlib,libppv_lite86-6eb742765e7cd1a7.rlib,libzerocopy-4bc3beda8a77cfdd.rlib,librand_core-f58de05815d27c8c.rlib,libgetrandom-60e8f95502be50c0.rlib,liblibc-b4e3ea87c31890b7.rlib,libcfg_if-fab19221290f8bbb.rlib,libgodot-5088a0b231bce29e.rlib,libgodot_core-7a01f5e16d89c050.rlib,libgodot_cell-2c8ea8db76081be3.rlib,libglam-8e30c70db285be24.rlib,libgodot_ffi-a3dbe1f0968e09be.rlib,libstd-9d21705d1e98481a.rlib,libpanic_unwind-1526744daa4904ad.rlib,librustc_demangle-0da3df4849c5a174.rlib,libstd_detect-37b68885def5b9a1.rlib,libhashbrown-584c659b45052d14.rlib,librustc_std_workspace_alloc-9f86d26d310a9544.rlib,libminiz_oxide-25f87b4cf4f43fcc.rlib,libadler2-107565b3c955937d.rlib,libunwind-eeec7a8114d2e3b6.rlib,libcfg_if-e5d75bb0875b4c00.rlib,liblibc-a1f0f269d50a87aa.rlib,liballoc-c50c0616ecc39485.rlib,librustc_std_workspace_core-ac9f390e10f3ae53.rlib,libcore-0a0a0ec040161aba.rlib,libcompiler_builtins-74d69639f1ae3b8a.rlib}.rlib" "-B<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/bin/gcc-ld" "--target=wasm32-unknown-emscripten" "-sDISABLE_EXCEPTION_CATCHING=0" "-o" "/home/user/projects/ProjectsGodot/dodge-the-creeps/rust/target/wasm32-unknown-emscripten/release/deps/dodge_the_creeps.wasm" "-O3" "-g0" "-pthread" "-sSIDE_MODULE=2" "-sABORTING_MALLOC=0" "-sWASM_BIGINT"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: emcc: warning: -sSIDE_MODULE + pthreads is experimental [-Wexperimental]
          Unknown option '--enable-bulk-memory-opt'
          emcc: error: '/home/user/APPS/Godot/utils/emsdk-4.0.7/upstream/bin/wasm-opt --strip-target-features --post-emscripten --pass-arg=post-emscripten-side-module -O3 --low-memory-unused --pass-arg=directize-initial-contents-immutable /home/user/projects/ProjectsGodot/dodge-the-creeps/rust/target/wasm32-unknown-emscripten/release/deps/dodge_the_creeps.wasm -o /home/user/projects/ProjectsGodot/dodge-the-creeps/rust/target/wasm32-unknown-emscripten/release/deps/dodge_the_creeps.wasm --mvp-features --enable-threads --enable-bulk-memory --enable-bulk-memory-opt --enable-call-indirect-overlong --enable-multivalue --enable-mutable-globals --enable-nontrapping-float-to-int --enable-reference-types --enable-sign-ext' failed (returned 1)
          

warning: `dodge-the-creeps` (lib) generated 1 warning
error: could not compile `dodge-the-creeps` (lib) due to 1 previous error; 1 warning emitted

In addition to emcc version 3.1.62, I also tried 3.1.73 and the latest version, but without success.

I suspect that I may need to downgrade my Rust version, but I'm not sure how to determine which version of Rust I need. I might also need some other version of emcc, but I also don't know how to figure out which one is required.

I also tried disable multi-threading support, but the error still persists for the release version.

[Bromeon]

This came up on Discord.
Can you try if using emsdk v3.1.74 would also work for you?

[SoftHardcore]

Thx, this worked with v3.1.74. Can you tell me how to find out in the future what emsdk version is required?

[Bromeon]

We should update the book.

It's a bit annoying because this keeps changing all the time. The Godot-Wasm-Rust ecosystem is extremely brittle, which is also why our Wasm support is still experimental.

Maybe we can leave this issue open until the book is updated 🤔