em++ silently fails if function name contains a template

[MartinFillon]

Hi, I am currently experimenting with em++ and found out that when a function (see following code) name contains a template the compilation will succeed but you cannot access the function. Javascript will say that the symbol doesn't exists. Embind will generate the right types but the function is unreachable. Is it intended that it is not reachable ? Is it intended to fail silently ?

The relevant code:

        emscripten::register_type<Component>("Component", "{name: string, [key: string]: any}");
        emscripten::register_type<ComponentNames>(
            "ComponentNames<T extends Component[]>", "T extends [infer First, ...infer Rest] ? First[\"name\"] | ComponentNames<Rest> : never"
        );
        emscripten::register_type<ComponentForName>(
            "ComponentForName<T extends Component[], N extends string>",
            "T extends [infer First, ...infer Rest] ? First[\"name\"] extends N ? First : ComponentForName<Rest, N> : never;"
        );

        emscripten::register_type<ZZ>(
            "ZipperResult<T extends Component[]>", "{ [K in ComponentNames<T>]: ComponentForName<T, K extends string ? K : never>; };"
        );

        emscripten::register_type<ZipperOutput>("ZipperResult<T>");

// Class definition...
            .function("getZipper<T extends Component[]>", &Registry::get_zipper)

The same thing happens with a function such as:

int add(int a, int b) {
 return a + b;
}
// yes this doesn't make sens but this is an example
emscripten::function("add<N>", &add);

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.19 (08e2de1031913e4ba7963b1c56f35f036a7d4d56)
clang version 22.0.0git (https:/github.com/llvm/llvm-project 12f392cff10fcc70b4ec4f01ab386922742e9136)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /home/fexkoser/dev/emsdk/upstream/bin

Full link command and output with -v appended:

em++ wasm/SparseArray.o wasm/Entity.o wasm/Utils.o wasm/Registry.o -O3 --no-entry --bind -sNO_DISABLE_EXCEPTION_CATCHING -sEXPORT_EXCEPTION_HANDLING_HELPERS -v -s MODULARIZE=1 -s EXPORT_ES6=1 -s ENVIRONMENT=web --emit-tsd libecs.d.ts -o lib/libecs.js
 /home/fexkoser/dev/emsdk/upstream/bin/clang --version
 /home/fexkoser/dev/emsdk/upstream/bin/wasm-ld -o lib/libecs.wasm wasm/SparseArray.o wasm/Entity.o wasm/Utils.o wasm/Registry.o -lembind-rtti -L/home/fexkoser/dev/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -L/home/fexkoser/dev/emsdk/upstream/emscripten/src/lib -lGL-getprocaddr -lal -lhtml5 -lstubs -lnoexit -lc -ldlmalloc -lcompiler_rt -lc++ -lc++abi -lsockets -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr /tmp/tmpbhxqv5tplibemscripten_js_symbols.so --strip-debug --export=_emscripten_stack_alloc --export=__getTypeName --export=__cxa_can_catch --export=__cxa_increment_exception_refcount --export=__cxa_decrement_exception_refcount --export=setThrew --export=__cxa_free_exception --export=__wasm_call_ctors --export=emscripten_stack_get_current --export=_emscripten_stack_restore --export=__get_exception_message --export=free --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-table -z stack-size=65536 --no-growable-memory --initial-heap=16777216 --no-entry --table-base=1 --global-base=1024
 /home/fexkoser/dev/emsdk/upstream/bin/llvm-objcopy lib/libecs.wasm lib/libecs.wasm '--remove-section=.debug*' --remove-section=producers --remove-section=name
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/compiler.mjs -
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/compiler.mjs -
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /tmp/emscripten_temp_x1yssint/tsgen.js /tmp/emscripten_temp_x1yssint/embind_generated_output.js
 /home/fexkoser/dev/emsdk/upstream/bin/wasm-opt --strip-target-features --post-emscripten -O3 --low-memory-unused --zero-filled-memory --pass-arg=directize-initial-contents-immutable --no-stack-ir lib/libecs.wasm -o lib/libecs.wasm --mvp-features --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
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /tmp/emscripten_temp_x1yssint/libecs.js AJSDCE --minify-whitespace --export-es6 -o /tmp/emscripten_temp_x1yssint/libecs.jso1.js
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /tmp/emcc_acorn_info_dga6tfir.js emitDCEGraph --no-print --export-es6
 /home/fexkoser/dev/emsdk/upstream/bin/wasm-metadce --graph-file=/tmp/emcc_dce_graph_vs_5wk_8.json lib/libecs.wasm -o lib/libecs.wasm --mvp-features --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
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /tmp/emcc_acorn_info_2rq8jhen.js applyDCEGraphRemovals --minify-whitespace --export-es6 -o /tmp/emscripten_temp_x1yssint/libecs.jso2.js
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /tmp/emscripten_temp_x1yssint/libecs.jso2.js AJSDCE --minify-whitespace --export-es6 -o /tmp/emscripten_temp_x1yssint/libecs.jso3.js
 /home/fexkoser/dev/emsdk/upstream/bin/wasm-opt --minify-imports-and-exports-and-modules --optimize-level=3 --shrink-level=0 --optimize-stack-ir lib/libecs.wasm -o lib/libecs.wasm --mvp-features --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
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /tmp/emcc_acorn_info_gkis97g3.js applyImportAndExportNameChanges --minify-whitespace --export-es6 -o /tmp/emscripten_temp_x1yssint/libecs.jso4.js
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/preprocessor.mjs - modularize.js --expand-macros
 /home/fexkoser/dev/emsdk/node/22.16.0_64bit/bin/node /home/fexkoser/dev/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /tmp/tmpe20c6_10.js --minify-whitespace --export-es6 -o /tmp/tmpe20c6_10.jso5.js

[sbc100]

The emscripten::function calls need to be placed inside and EMSCRIPTEN_BINDINGS block. In your small example I don't see that so wanted to check that you are indeed doing that.

[MartinFillon]

I indeed have it, I omitted it for clarity sake.

[brendandahl]

emscripten::function is not meant to have TS in the name. The TS definition generated in the add case above is wrong, it should really be something like 'add<N>'(_0: number, _1: number): number;. The function is reachable from JS e.g. console.log(Module['add<N>']);