math.cos reveals OS
part1: background / obsolete code?
I can't find the old ticket, but it's probably relevant- it was about the implementation of higher math functions
see: https://ghacksuserjs.github.io/TorZillaPrint/TorZillaPrint.html#math also see: https://fpcentral.tbb.torproject.org/fp
However (unless I made a mistake), I see no difference in these returned values in a vanilla ESR60, or FF60 thru to 66 as compared to Tor Browser. So I am not sure if the old patch is still required, or has even been rebased.
asinh(1) 0.8813735870195429
acosh(1e300) Infinity
atanh(0.5) 0.5493061443340548
expm1(1) 1.7182818284590455
cbrt(100) 4.641588833612778
log1p(10) 2.3978952727983707
sinh(1) 1.1752011936438016
cosh(10) 11013.232920103324
tanh(1) 0.7615941559557649
part2: math.cos Windows: FF vs TB
results: see attachment test: https://thorin-oakenpants.github.io/testing/ (for as long as I leave it there)
I do not know if that ticket/patch causes this, but there is a difference between TB vs FF for no discernible reason (e.g Linux doesn't differ between FF and TB)
Look at the first result. FF: minus 0.374... vs TB plus 0.840...
part3: math.cos reveals platform
finally, to the meat and potatoes. See attachment. I'm using math.cos because it always returns a value between -1 and 1 (i.e no NaN or Infinity). The following tests show that, so far, the last four values can be used to detect windows or Linux, and so far one Android major version (v5.*). I am fully expecting the first four value to betray other Android and macOS/macOS X. My testing is incomplete, but enough to prove os FP'ing