On non-glibc based systems we cannot unconditionally use the
__GLIBC_PREREQ macro as it gets expanded before evaluation. Instead,
if it is undefined, define it to 0.
We should also always declare these functions on non-glibc based
systems. And on systems with a new enough glibc, which provides these
functions, we should still provide the declarations if _GNU_SOURCE
is *not* defined.
Reported-by: Jörg Krause <joerg.krause@embedded.rocks>
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 makes sure the “standard” inclusion protectors are in place, as at
least some FreeBSD kernel headers expect these to be defined to do some
sanity checks.
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.
