Generic error if FS.createPreloadedFile parent doesn't exist

[curiousdannii]

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.59 (0e4c5994eb5b8defd38367a416d0703fd506ad81)
clang version 19.0.0git (https:/github.com/llvm/llvm-project df762a1643bb5b0b3c907611d118c82d4b68a39d)

I'm trying to preload some files (in a pre-js file):

Module.preRun = () => {
    FS.createPreloadedFile('/data', 'journey-r83-s890706.z6', 'journey-r83-s890706.z6', true, false)
    FS.createPreloadedFile('/data', 'Journey.blb', 'Journey.blb', true, false)
}

Since I forgot to create the /data folder first I'm getting a console errors, but they're very generic and unhelpful. Enabling -sASSERTIONS doesn't make a difference.

sfrotz.js:3406 Uncaught <generic error, no stack>
sfrotz.html:195 [post-exception status] Exception thrown, see JavaScript console
sfrotz.js:3406 Uncaught <generic error, no stack>

[sbc100]

I tried to reproduce this in node that is did show a reasonable error:

$ emcc --pre-js=pre.js test/hello_world.c -sFORCE_FILESYSTEM
$ node a.out.js 

/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:134
      throw ex;
      ^
Loading data file "journey-r83-s890706.z6" failed.
(Use `node --trace-uncaught ...` to show where the exception was thrown)

In the browser I see Uncaught Loading data file "journey-r83-s890706.z6" failed. including a full stack trace.

Perhaps I'm misunderstanding something?

[curiousdannii]

Huh. I was doing it in the browser. But even in an O0 build with ASSERTIONS on I never saw a specific error like that.

[sbc100]

Can you share the full set of link flags you are using?

Are you saying you don't see any kind of stack trace in devtools?

[curiousdannii]

There is a stack trace, it's just the main error message that's generic:

sfrotz.js:3593 Uncaught <generic error, no stack>
	(anonymous)	@	sfrotz.js:3593
	staticInit	@	sfrotz.js:3592
	(anonymous)	@	sfrotz.js:9677
	load (async)		
	readAsync	@	sfrotz.js:135
	asyncLoad	@	sfrotz.js:1729
	FS_createPreloadedFile	@	sfrotz.js:1787
	Module.preRun	@	sfrotz.js:41

Line 3593 is from here:

  staticInit() {
        // Some errors may happen quite a bit, to avoid overhead we reuse them (and suffer a lack of stack info)
        [44].forEach((code) => {
          FS.genericErrors[code] = new FS.ErrnoError(code);
          FS.genericErrors[code].stack = '<generic error, no stack>';
        });
  
        FS.nameTable = new Array(4096);
  
        FS.mount(MEMFS, {}, '/');
  
        FS.createDefaultDirectories();
        FS.createDefaultDevices();
        FS.createSpecialDirectories();
  
        FS.filesystems = {
          'MEMFS': MEMFS,
          'IDBFS': IDBFS,
        };
      },

/emsdk/upstream/emscripten/emcc src/common/frotz_common.a src/sdl/frotz_sdl.a src/blorb/blorblib.a 
src/common/frotz_common.a -o sfrotz.js --use-port=freetype --use-port=libjpeg --use-port=libpng
--use-port=sdl2 --use-port=sdl2_mixer --use-port=zlib -lidbfs.js --js-library ../src/frotz-library.js
--pre-js ../src/preamble.js --profiling-funcs -sALLOW_MEMORY_GROWTH -sASYNCIFY
-sENVIRONMENT=web -lm

Maybe ASNCIFY or ENVIRONMENT=web muddles things?