Fix mask calculation to avoid incorrect 0 values caused by compiler optimization

[bdutro]

Problem

On my machine, iio-sensor-proxy was returning all 0's for my accelerometer sensor values. It turns out that the bits_used for this sensor is 32, which makes the mask calculation:

*mask = (1 << 32) - 1;

If the compiler interprets the 1 literals as 32-bit ints, it generates undefined behavior depending on compiler version and optimization level. In my case, it optimizes out the shift, so the mask value becomes

*mask = (1) - 1;

With a mask value of 0, iio-sensor-proxy will always return 0 for every axis.

Fix

Explicitly mark the 1 literals as unsigned 64-bit ints so that we never encounter the undefined behavior case.

[hadess]

I've made some changes to the patch itself and to the commit message in https://github.com/hadess/iio-sensor-proxy/pull/272 Could you please double-check that it still works for you?

Thanks for the patch!

[bdutro]

Yep, that version works for me.

[hadess]

Thanks!