iio: Fix possible incorrect mask calculation

On some machines, iio-sensor-proxy was returning all 0's for IIO 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.
On my system, 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.

Avoid incorrect 0 values caused by compiler optimization.

Closes: #270
This commit is contained in:
Brett Dutro
2019-05-18 21:39:58 -05:00
committed by hadess
parent b320a3207b
commit 9615ceac7c

View File

@@ -136,9 +136,9 @@ iioutils_get_type (unsigned *is_signed,
*be = (endianchar == 'b'); *be = (endianchar == 'b');
*bytes = padint / 8; *bytes = padint / 8;
if (*bits_used == 64) if (*bits_used == 64)
*mask = ~0; *mask = ~G_GUINT64_CONSTANT(0);
else else
*mask = (1 << *bits_used) - 1; *mask = (G_GUINT64_CONSTANT(1) << *bits_used) - G_GUINT64_CONSTANT(1);
*is_signed = (signchar == 's'); *is_signed = (signchar == 's');
g_debug ("Got type for %s: is signed: %d, bytes: %d, bits_used: %d, shift: %d, mask: 0x%" G_GUINT64_FORMAT ", be: %d", g_debug ("Got type for %s: is signed: %d, bytes: %d, bits_used: %d, shift: %d, mask: 0x%" G_GUINT64_FORMAT ", be: %d",