in pkgtools/libnbcompat/files/nbcompat/queue.h, there appears:
#define SLIST_EMPTY(head) ((head)->slh_first == NULL)
which leads to
clang -O2 -I/usr/pkg/include -DHAVE_NBCOMPAT_H=1 -I/usr/pkgsrc/pkgtools/pkgin/work/libnbcompat -I/usr/pkg/include -DPKGIN_VERSION=\""0.9.3 for Darwin-13.4.0 x86_64"\" -DHAVE_NBCOMPAT_H=1 -I/usr/pkgsrc/pkgtools/pkgin/work/libnbcompat -I/usr/pkg/include -g -DLOCALBASE=\"/usr/pkg\" -DPKG_SYSCONFDIR=\"/usr/pkg/etc\" -DPKG_DBDIR="\"/var/db/pkg\"" -DDEF_LOG_DIR="\"/var/db/pkg\"" -DPKGIN_DB=\"/var/db/pkgin\" -DPKGTOOLS=\"/usr/pkg/sbin\" -DHAVE_CONFIG_H -D_LARGEFILE_SOURCE -D_LARGE_FILES -DCHECK_MACHINE_ARCH=\"x86_64\" -Iexternal -I. -I/usr/pkg/include -c depends.c
depends.c:124:33: warning: equality comparison with extraneous parentheses [-Wparentheses-equality]
if (((&r_plisthead)->slh_first == ((void*)0))) {
~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
On one hand, the parentheses-equality warning is reasonable, but with
parens around a macro expansion to ensure that what looks like a
function behaves like a function, it isn't reasonable.