wasm-ld --export-all does not work with wasm-bindgen

[jkelleyrtp]

Describe the Bug

I've implemented WASM hot patching for Rust.

DioxusLabs/dioxus#3797 (comment)

432065352-b81f1a60-b6b2-422d-a536-d9e0bcd75221.mp4

Part of this working properly requires every symbol from the dependency rlibs to make it into the final executable. All other platforms (mac/win/linux/android/ios) have facilities to force all symbols (--no-gc-sections, --whole-archive). Unfortunately, wasm-bindgen is the one tool that always runs GC and doesn't give an option to not run GC.

This means I need to prevent symbols from being dissolved by the wasm-bindgen GC pass, but relying on markers is fraught with issues and will likely break in the future. I hacked together something that barely works today but I can't expect it to work tomorrow:

    // We're going to add *all* the imports that start with __wbindgen to a function that's exported
    // This prevents them from being dissovlved
    for (imp, f) in imports {
        let name = &module.imports.get(imp).name;
        if name.starts_with("__wbindgen") && !name.starts_with("__wbindgen_describe") {
            module.exports.add(name, f);
            module.exports.add(&format!("{name}_subsecond"), f);
            tracing::info!("Hoisting import -> {name}");
            already_exported.insert(name.clone());
            make_indirect.push(f);
        }
    }

    for (name, index) in symbols.code_symbol_map.iter() {
        let func = module.funcs.get(ids[*index]);

        if let FunctionKind::Local(_) = &func.kind {
            if !already_exported.contains(*name) && !name_is_bindgen_symbol(name) {
                module.exports.add(name, func.id());
                already_exported.insert(name.to_string());
            }

            if !name_is_bindgen_symbol(name) {
                if !ifuncs.contains(&func.id()) {
                    make_indirect.push(func.id());
                }
            }
        }
    }

fn name_is_bindgen_symbol(name: &str) -> bool {
    name.contains("__wbindgen_describe")
        || name.contains("wasm_bindgen..describe..WasmDescribe")
        || name.contains("wasm_bindgen..closure..WasmClosure$GT$8describe")
        || name.contains("wasm_bindgen7closure16Closure$LT$T$GT$4wrap8describe")
        || name.contains("__wbindgen_describe_closure")
        || name.contains("__wbindgen_externref_xform")
}

If I force the wasm-bindgen intrinsics into an export, then the wasm-bindgen pass deletes them. If I put them in the ifunc table, the generated JS is invalid.

These imports:

12:20:22 [dev] Hoisting import -> __wbindgen_function_table
12:20:22 [dev] Hoisting import -> __wbindgen_number_new
12:20:22 [dev] Hoisting import -> __wbindgen_neg
12:20:22 [dev] Hoisting import -> __wbindgen_string_get
12:20:22 [dev] Hoisting import -> __wbindgen_throw
12:20:22 [dev] Hoisting import -> __wbindgen_bigint_from_i64
12:20:22 [dev] Hoisting import -> __wbindgen_in
12:20:22 [dev] Hoisting import -> __wbindgen_boolean_get
12:20:22 [dev] Hoisting import -> __wbindgen_externref_table_grow
12:20:22 [dev] Hoisting import -> __wbindgen_string_new
12:20:22 [dev] Hoisting import -> __wbindgen_error_new
12:20:22 [dev] Hoisting import -> __wbindgen_is_bigint
12:20:22 [dev] Hoisting import -> __wbindgen_debug_string
12:20:22 [dev] Hoisting import -> __wbindgen_exports
12:20:22 [dev] Hoisting import -> __wbindgen_array_push
12:20:22 [dev] Hoisting import -> __wbindgen_bigint_from_u64
12:20:22 [dev] Hoisting import -> __wbindgen_jsval_eq
12:20:22 [dev] Hoisting import -> __wbindgen_memory
12:20:22 [dev] Hoisting import -> __wbindgen_biguint64_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_is_object
12:20:22 [dev] Hoisting import -> __wbindgen_symbol_named_new
12:20:22 [dev] Hoisting import -> __wbindgen_object_drop_ref
12:20:22 [dev] Hoisting import -> __wbindgen_is_string
12:20:22 [dev] Hoisting import -> __wbindgen_object_clone_ref
12:20:22 [dev] Hoisting import -> __wbindgen_cb_drop
12:20:22 [dev] Hoisting import -> __wbindgen_is_undefined
12:20:22 [dev] Hoisting import -> __wbindgen_bigint_from_u128
12:20:22 [dev] Hoisting import -> __wbindgen_symbol_anonymous_new
12:20:22 [dev] Hoisting import -> __wbindgen_externref_table_set_null
12:20:22 [dev] Hoisting import -> __wbindgen_number_get
12:20:22 [dev] Hoisting import -> __wbindgen_externref_heap_live_count
12:20:22 [dev] Hoisting import -> __wbindgen_rethrow
12:20:22 [dev] Hoisting import -> __wbindgen_uint16_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_float32_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_as_number
12:20:22 [dev] Hoisting import -> __wbindgen_lt
12:20:22 [dev] Hoisting import -> __wbindgen_uint32_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_int32_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_int8_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_bigint_get_as_i64
12:20:22 [dev] Hoisting import -> __wbindgen_uint8_clamped_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_bigint64_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_uint8_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_float64_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_bigint_from_i128
12:20:22 [dev] Hoisting import -> __wbindgen_checked_div
12:20:22 [dev] Hoisting import -> __wbindgen_module
12:20:22 [dev] Hoisting import -> __wbindgen_is_function
12:20:22 [dev] Hoisting import -> __wbindgen_int16_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_array_new
12:20:22 [dev] Hoisting import -> __wbindgen_jsval_loose_eq

Will end up leaving the __wbindgen_externref_xform__ import in the generated JS bindings:

import * as __wbg_star5 from '__wbindgen_externref_xform__';

If I hoist every symbol (ie with --export-all) then the describe functions stick around and aren't valid JS.

// ...
// these imports still remain
import * as __wbg_star5 from '__wbindgen_externref_xform__';
import * as __wbg_star6 from '__wbindgen_placeholder__';

// ...
// this is not valid JS
function __wbg_adapter_102(arg0, arg1) {
    _assertNum(arg0);
    _assertNum(arg1);
    wasm._ZN132_$LT$dyn$u20$core..ops..function..FnMut$LT$$LP$$RP$$GT$$u2b$Output$u20$$u3d$$u20$R$u20$as$u20$wasm_bindgen..closure..WasmClosure$GT$8describe6invoke17h4336be12b5d12f09E(arg0, arg1);
}

Ideally, I can pass --export-all, get every interface properly wasm-bindgen-ed, and then load subsequent patches that don't require any bindgen at all. Currently it's not clear if I can even load the patches without running wasm-bindgen on them (due to the transform passes), and if I have to, then I can't use dynamic linking because of #4493.

Steps to Reproduce

Running rustc with the export-all flag will trigger the issues:

cargo rustc --package app --target wasm32-unknown-unknown -Clinker-arg=-Wl,--export-all

Expected Behavior

You can export all symbols from a wasm module.

Actual Behavior

The generated JS is invalid.

Additional Context

Add any other context about the problem here.