Spot on Alon :) It works if I hardwire just the C library (with the EM_JS functions) to the wasm32-emscripten triple.
The Zig code needs to be compiled either with wasm32-wasi or wasm32-freestanding, when using wasm32-emscripten, parts of the Zig stdlib won't compile. Also, when I tried to use wasm32-freestanding with the C code, then wasm-ld complained about some missing stack-check functions (don't have the exact symbol at hand currently). ...I think I have enough to build a little 'proof-of-concept', even though it's a bit hacky :) Thanks! -Floh. On Saturday, 29 January 2022 at 18:58:53 UTC+1 [email protected] wrote: > Sam can confirm, but I would guess perhaps the emscripten triple is > necessary. That is, clang and/or wasm-ld might do something for EM_JS code > but only in emscripten mode. > > If we can confirm that then we should definitely get a bug filed on Zig - > hopefully it would be easy to add support for the emscripten triple there > and open up a bunch of use cases... > > On Sat, Jan 29, 2022 at 9:12 AM Floh <[email protected]> wrote: > >> I'm currently tinkering with bringing one of my toy Zig projects to the >> web via >> Alon's nice gist here which uses emcc only for the linker step: >> >> https://gist.github.com/kripken/58c0e640227fe5bac9e7b30100a2a1d3 >> >> ...and it *nearly* works except for code that uses EM_JS() macros. >> >> The project (https://github.com/floooh/pacman.zig) consists of some C >> code (my cross-platform 'sokol headers') which uses EM_JS() quite >> extensively (very handy for STB-style single-file libraries), and at the >> top, the "game code" is written in Zig. >> >> I'm compiling all code with Zig with the wasm32-wasi target >> (wasm32-emscripten exists, but currently doesn't seem to be supported by >> the Zig compiler), and then use emcc for linking. >> >> Long story short, it works except for the one problem that emcc cannot >> resolve any functions which have been defined with EM_JS(). If I compile >> the same library with emcc instead of Zig it works. >> >> So my question is: does emcc also do some "EM_JS() magic" when compiling >> the source code which contains EM_JS macros? Maybe I'm missing some Clang >> command line options which emcc inserts? >> >> The errors look like this: >> >> error: undefined symbol: sapp_js_add_clipboard_listener (referenced by >> top-level compiled C/C++ code) >> >> Followed by: >> >> warning: _sapp_js_add_clipboard_listener may need to be added to >> EXPORTED_FUNCTIONS if it arrives from a system library >> ...there's also a single warning about malloc: >> >> ...if I compile with "-s ERROR_ON_UNDEFINED_SYMBOLS=0", then the code >> breaks at runtime failing to resolve those EM_JS() functions, e.g.: >> >> "missing function: sapp_js_pointer_init" >> >> Compiling the same static link library with emcc, it magically works. >> >> If I look at both libraries with nm I don't see much of a difference, >> e.g. here's the relevant parts from the emcc-compiled library, every EM_JS >> symbol has an "D __em_js..." entry, and a matching "U sapp_js..." entry, >> e.g.: >> >> 0000185f D __em_js__sapp_js_add_beforeunload_listener >> ... >> U sapp_js_add_beforeunload_listener >> ... >> >> The Zig-compiled library has the same entries: >> >> 00001841 D __em_js__sapp_js_add_beforeunload_listener >> ... >> U sapp_js_add_beforeunload_listener >> ... >> >> ...yet one library (the zig-compiled) produces linker errors for those >> symbols, and the other (emcc-compiled) works. >> >> Clearly I'm missing something. I was expecting that all the EM_JS() magic >> is in the linker (by extracting the __em_js_* Javascript source code >> strings, and then "somehow" providing the C function import). Any ideas >> what I'm missing? >> >> Thanks! >> -Floh. >> >> >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "emscripten-discuss" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/emscripten-discuss/15129292-2f07-44d9-99a9-a27ac4721a0cn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/emscripten-discuss/15129292-2f07-44d9-99a9-a27ac4721a0cn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/emscripten-discuss/ad13a6a8-0248-406d-ba91-591bcec62e54n%40googlegroups.com.
