util: MAX_FROM_BITS() should be unsigned

MAX_FROM_BITS() computes the maximum value representable in a number of
bits.  The expression for that is an unsigned value, but we explicitly cast
it to a signed int.  It looks like this is because one of the main users is
for FD_REF_MAX, which is used to bound fd values, typically stored as a
signed int.

The value MAX_FROM_BITS() is calculating is naturally non-negative, though,
so it makes more sense for it to be unsigned, and to move the case to the
definition of FD_REF_MAX.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/util.h b/util.h
index 86f1a7e..53bb54b 100644
--- a/util.h
+++ b/util.h
@@ -43,7 +43,7 @@
 #define ROUND_DOWN(x, y)	((x) & ~((y) - 1))
 #define ROUND_UP(x, y)		(((x) + (y) - 1) & ~((y) - 1))
 
-#define MAX_FROM_BITS(n)	((int)((1U << (n)) - 1))
+#define MAX_FROM_BITS(n)	(((1U << (n)) - 1))
 
 #define BIT(n)			(1UL << (n))
 #define BITMAP_BIT(n)		(BIT((n) % (sizeof(long) * 8)))