Printing to stderr

[Arve Knudsen]

Hello

Does one have to do anything in particular to have stderr output directed to the browser's console in the Emscripten-generated JS code?

Currently, with my ChucK port, I do not see anything being printed to stderr (nor stdout).

Thanks,

Arve

[Floh]

Did you test with the default shell html page? I think all output goes to user-defined functions Module.print or Module.printErr, see here:

https://github.com/kripken/emscripten/blob/33c92f65f9641fac702fe219e35aeb9b62cb748f/src/shell.html#L1223

For an example of a (very simple) self-rolled shell html page look here (emsc.html and emsc.js):

https://github.com/floooh/oryol/tree/master/web

Cheers,

-Floh.

[Arve Knudsen]

Thanks, I'll have to try. But for now I have a flight to catch...

Arve

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[Arve Knudsen]

I've tried generating a shell HTML page, and yes it does print stderr to the console. Also, if I include an a.out.js file (generated by em++ without options) in a hand-written HTML page, stderr gets printed to the console as well. So, stderr printing should work, the question is why it's not working in the ChucK case.

Does anyone have any hints as to debugging why Module.printErr doesn't get called for printing to stderr? I've deduced that Module.printErr does in fact write to the console, because Emscripten generates one (successfull) call to it (to inform of 'pre-main prep time'). As such, it seems to me that the code generated from ChucK ends up not calling Module.printErr for printing to stderr.

Arve

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[Arve Knudsen]

OK, I found out why nothing was being printed. I had forgot to write newlines, so output was only buffered, and it turns out fflush doesn't work either: https://github.com/kripken/emscripten/issues/2770.

Arve