Some systems such as Windows or musl-libc based ones do not have these
BSD extensions. In addition libbsd itself is making use of the warnx()
functions, so we better provide these interfaces in case they are
missing.
Do not depend on the system vwarn() and verr() functions to implement
the *c() variants, as the system might actually lack any of the <err.h>
BSD extensions.
These headers are not available on Windows. <bsd/sys/cdefs.h> ensures
that __has_include() and __has_include_next() are defined.
Signed-off-by: Guillem Jover <guillem@hadrons.org>
Glibc tends to include standard headers with special definitions
that make few declarations or macros visible, this stomps over the
overlay #include_next <> logic.
Based-on-patch-by: Robert Millan <rmh@debian.org>
This means that software being ported should not need to be modified in
the usual case, as the libbsd headers will take over the standard
namespace and fill the missing gaps, and include the system headers.
To use this the new libbsd-transparent.pc file can be used through
pkg-config, which should end up doing the right thing.
