- Add a new macro to klist.h: kl_empty()
The whole point of abstract data structures is to avoid reimplementing
common actions. The emptiness test seems to be such an action.
- Add a new function attribute to func_attr.h: FUNC_ATTR_UNUSED
Some of the many functions created by the macros in klist.h may end up not
being used. Unused functions cause compilation errors as we compile with
-Werror. To mark those functions as possibly unused we can use the
FUNC_ATTR_UNUSED now.
- Pass `Event` by value
`Event` is such a small struct that I don't think we should allocate heap space
and pass it by reference. Let's use the stack and memory cache in our favor
passing it by value.
The attributes in question are:
- nonnull: specify whether a function argument cannot/may not be null
- returns_nonnull: specify whether a function will not return a null
pointer (example: xmalloc can't return null, so it should be annotated as
such). Only available from gcc 4.9 onwards.
Currently these attributes are only supported by gcc.
The attribute was removed in commit c047507 in the clang repository as it
was never properly implemented anyway. This fixes compiling with clang 3.5.
Fixes issue #429
