This macro is a variant on CONTAINER_OF that takes an object pointer
instead of a type name as its second argument. In the following commit
this will simplify many users of CONTAINER_OF.
On sparc, GCC would issue the following warning for every use of
CONTAINER_OF:
warning: cast increases required alignment of target type
This is a false positive: assuming that the data structure that it is
applied to was allocated properly, the use of CONTAINER_OF to reach it is
valid. And if it was not allocated properly, then code that accesses it
other ways will have trouble too.
Some systems complain when certain functions' return values are not
checked. This commit fixes those warnings.
Creating ignore() function suggested by Ben Pfaff.
ROUND_UP rounds up to a multiple of a given value. That means that
bitmap_allocate() was allocating one byte for each bit in the bitmap,
which is clearly excessive.
Instead, just allocate one bit for every bit in the bitmap.
