Rounding error passing large integers

[jneb]

If you have a integer number of more than 53 bits (and less than 64 obviously) it will be rounded to float when passed from lua to python:

>>> lua.lua_version
(5, 4)
>>> lua.eval("1000000000*1000000000-1")
1000000000000000000
>>> lua.eval("1000000000*1000000000-1 .. ''")
'999999999999999999'

Here you can see that the calculation didn't overflow, proving that a 64 bit integer was produced by lua, but the number got lost in translation to python.
This is probably not noticed but many, but pretty annoying when you encounter it!

In the code I found the function py_from_lua that apparently is supposed to do this correctly for versions >= 5.3, but it doesn't work for me (on pydroid 3).

[jneb]

After trying to figure out what the code does, I guess the error is near line 1320 of _lupa.pyx
After having checked for the right version of lua and python, it does:
integer = lua.lua_tointeger(L, n)
This function tointeger is part of lua itself and doesn't do anything for integers, so I guess something else was intended here.

[scoder]

Which Lupa version are you using? Lupa 2.0 is still unreleased.

https://github.com/scoder/lupa/blob/master/CHANGES.rst

[jneb]

That's 1.14.1: the version pipy provided. Considering it is fixed, that means that the actual issue is that the pipy version needs updating:-)