Is there anything nondeterministic here? The results on different OSes and
browsers should be 100% identical except for things like random numbers,
input events, etc. (unless you are seeing a browser bug).
For debugging purposes you can build with -s DETERMINISTIC=1 which will
force random numbers and timer events to be identical as well. Also worth
building with ASSERTIONS and SAFE_HEAP, as an error like this might be a
stack overflow or a heap corruption.
On Tue, Apr 3, 2018 at 7:50 AM, Jeff Schindler <jas...@gmail.com> wrote:
> We have some audio processing C code that we've brought to JS via
> emscripten. We're seeing odd behavior with the heap under certain
> conditions. We have a boolean value that we are setting, which is later
> checked to determine the processing path. In the right context, this
> boolean, which resides in the HEAP32 array, somehow gets changed and
> processing proceeds incorrectly. We are seeing this within a certain
> context only (so far) on Windows machines (tested in latest Chrome and
> Firefox). On Mac Chrome and Firefox, the HEAP32 check comes back as
> expected. What's really odd, and probably because of my naiveté on how
> emscripten actually does its work, is that upon debugging on the Mac, I can
> see that the first (and only the first) time the code checks the boolean,
> it's looking at a different location than I would expect it to look (ie it
> doesn't check the location that actually gets set when the boolean is
> set). On Windows, when it doesn't work, it always uses the expected
> location and on that first check, it has the wrong value. To further add
> confusion, we have another JS client app where we're using the exact same
> code and it works fine with it on the same Windows machine. If anyone has
> any insight at all, it'd be greatly appreciated!
>
> If it's useful, here are snippets of the relevant asm.js code:
>
> // set the boolean, where $0 is a passed parameter
> $0 = $0 | 0;
> var label = 0,
> sp = 0;
> sp = STACKTOP;
> HEAP32[(169880) >> 2] = $0;
>
> // check the boolean, where $1 is a passed parameter
> // the $6 var has the incorrect value on windows
> // on the mac, $4 is 339904 on the first check, and then 169889 thereafter
> // on windows, $4 is always 169889 when it fails
> // note that on the mac, both heap locations have the correct value
> $4 = ((($1)) + 24 | 0);
> $5 = HEAP32[$4 >> 2] | 0;
> $6 = ($5 | 0) != (0);
> $7 = ($0 | 0) != (2);
> $or$cond = $7 | $6;
> if ($or$cond) {
> return;
> }
>
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