commit b6160e034f66588dae324311d7e46426cff839da
Author: Mikolaj Golub <trociny@freebsd.org>
Date:   Sat Jan 25 20:05:06 2014 +0200

    Make dtrace(1) generate header files so that the same sources can be
    built either with or without dtrace probes, depending on if
    WITH_DTRACE is defined.

diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_program.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_program.c
index a325c42..b413077 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_program.c
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_program.c
@@ -560,7 +560,8 @@ dt_header_provider(dtrace_hdl_t *dtp, dt_provider_t *pvp, FILE *out)
 	dt_header_fmt_func(info.dthi_pfname, pvp->pv_desc.dtvd_name);
 
 #ifdef __FreeBSD__
-	if (fprintf(out, "#include <sys/sdt.h>\n\n") < 0)
+	if (fprintf(out,
+	    "#ifdef WITH_DTRACE\n#include <sys/sdt.h>\n#endif\n\n") < 0)
 		return (dt_set_errno(dtp, errno));
 #endif
 	if (fprintf(out, "#if _DTRACE_VERSION\n\n") < 0)

commit 4606de45452f4bfed72d6afe4f24906e77dde69a
Author: Mikolaj Golub <trociny@freebsd.org>
Date:   Sun Jul 14 20:47:05 2013 +0300

    Improvements to bsd.dtrace.mk:
    
    - Make makefiles that include bsd.dtrace.mk work when WITH_DTRACE
      is not defined.
    - Make it work with DTRACEOBJS containing any number of files.
    - Make it work when OBJDIR is not current directory.
    - Force removing old dtrace objects before generating new ones, as
      dtrace(1) refuses to rewrite them.
    - Make possible to specify additional dtrace(1) options (e.g.
      directory paths) via DTRACEFLAGS.

diff --git a/share/mk/bsd.dtrace.mk b/share/mk/bsd.dtrace.mk
index 518de30f..4c5469d 100644
--- a/share/mk/bsd.dtrace.mk
+++ b/share/mk/bsd.dtrace.mk
@@ -32,29 +32,34 @@
 # You must include this file before bsd.lib.mk or bsd.prog.mk.
 #
 
-.if defined(WITH_DTRACE)
+DTRACEHEADERS=	${DTRACEOBJS:S/o$/h/}
+DTRACESRCS=	${DTRACEOBJS:S/o$/d/}
+CLEANFILES+=	${DTRACEHEADERS}
 
-CFLAGS+=-DWITH_DTRACE
-DTRACEHEADERS=${DTRACEOBJS:S/o$/h/}
-DTRACESRCS=${DTRACEOBJS:S/o$/d/}
-CLEANFILES+=${DTRACEOBJS} ${DTRACEHEADERS}
+.for _DH in ${DTRACEHEADERS}
+${_DH}: ${_DH:R}.d
+	${DTRACE} ${DTRACEFLAGS} -C -h -s ${.ALLSRC}
+.endfor
 
-DPADD+=${LIBELF}
-LDADD+=-lelf
+beforedepend: ${DTRACEHEADERS}
 
-.if defined(PROG)
-_DTRACELINKING=${OBJS}
-OBJS+=${DTRACEOBJS}
-.else
-_DTRACELINKING=${SOBJS}
-SOBJS+=${DTRACEOBJS}
-.endif
+CFLAGS+=	-I${.OBJDIR}
+
+.if defined(WITH_DTRACE)
+
+CFLAGS+=	-DWITH_DTRACE
+CLEANFILES+=	${DTRACEOBJS}
+
+DPADD+=	${LIBELF}
+LDADD+=	-lelf
 
 ${DTRACEOBJS}:
 
-beforedepend:
-	${DTRACE} -C -h -s ${DTRACESRCS}
-beforelinking:
-	${DTRACE} -G -s ${DTRACESRCS} ${_DTRACELINKING:S/${DTRACEOBJS}//}
+beforelinking: ${DTRACESRCS}
+.if !empty(DTRACESRCS)
+	@rm -f ${DTRACEOBJS}
+	${DTRACE} ${DTRACEFLAGS} -G ${.ALLSRC:M*.d:S/^/-s /} \
+	    ${.ALLSRC:N*.d:tW:S/${DTRACEOBJS}//}
+.endif
 
 .endif