I'm moving right along with my experiments of getting the messaging stack of my wireless LED control system running in Node.js via Web Assembly (WA...
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I would be careful not to use "-s ERROR_ON_UNDEFINED_SYMBOLS=0" for too long, for this may turn build-time errors into run-time ones! The --js-library flag can be used for the JS glue code. You are certainly aware of this, but I think beginners should understand the risk :)
Good point about the dangers of
-s ERROR_ON_UNDEFINED_SYMBOLS=0, thanks!I'll confess, I haven't explored using the --js-library flag yet. A quick read suggested it wouldn't do what I needed it to do, but I also may just not have read deeply into it enough.
The thing is:
if, in your C++ code, you define something as:
extern int GetFoo();
Then, if you build the code, you'll get an undefined symbol error, UNLESS this function can be "seen" by emscripten. It can only see it if you put it in a js file that it knows of. That is, a file that is passed to the --js-library flag.
What I usually do is something like:
C++: extern "C" void SomeFunction();
JS (in library.js) : SomeFunction : function() { _SomeFunction() }
And _SomeFunction is declared in the JavaScript project where I load the wasm module in.
You can find more details here:
emscripten.org/docs/porting/connec...
HTH
I added a note in the text itself warning folks to be careful about undefined symbols. Thanks again!
Great article. Minor typo - should be strlen(str) rather than strlen(s).
Nice catch, and thanks for letting me know. It's fixed now.