bitset: introduce helpers to allocate a bitset at runtime

[royger]

Summary

Introduce some new helpers to declare and allocate a dynamic bitset, whose
size is not a constant.

Sponsored by: Citrix Systems R&D

[jhb]

I would only put BITSET_DEFINE_VAR in _bitset.h (unfortunate to have to split it, but the idea is that _foo.h is the minimum to let you define types so it can be used as a nested include).

I think you don't need BITSET_FREE(). It's not unusual for APIs to return data that the caller knows has to be freed with free() (e.g. strdup() in userland).

[royger]

Remove BITSET_FREE, and move BITSET_ALLOC to bitset.h

[kib]

sys/sys/bitset.h

195 ↗

(On Diff #15964)

Why _s, while you use non-prefixed names for other arguments ?

I suggest to put () around flags mf in the malloc.

[kib]

sys/sys/bitset.h

195 ↗

(On Diff #15964)

Hm, and why do you need p argument at all ? Why not leave it to the user

p = BITSET_ALLOC(1000, M_TMP, M_WAITOK);

[royger]

sys/sys/bitset.h

195 ↗

(On Diff #15964)

_s is used to keep the consistency between other macros in the file, where _s is also used to describe the size.

195 ↗

(On Diff #15964)

This is a remaining of a previous implementation, I will remove p and use an assignment, thanks.