Below is a diff that updates devel/acpica to 20170929. I don't have much experience with this software but iasl -d seems to work properly.
Thanks, Caspar Schutijser Index: Makefile =================================================================== RCS file: /cvs/ports/devel/acpica/Makefile,v retrieving revision 1.21 diff -u -p -r1.21 Makefile --- Makefile 18 Mar 2017 21:37:55 -0000 1.21 +++ Makefile 15 Oct 2017 08:14:35 -0000 @@ -3,7 +3,7 @@ ONLY_FOR_ARCHS = amd64 i386 COMMENT = reference implementation of ACPI tools -DISTNAME = acpica-unix-20170303 +DISTNAME = acpica-unix-20170929 PKGNAME = ${DISTNAME:S/-unix//} CATEGORIES = devel Index: distinfo =================================================================== RCS file: /cvs/ports/devel/acpica/distinfo,v retrieving revision 1.11 diff -u -p -r1.11 distinfo --- distinfo 18 Mar 2017 21:37:55 -0000 1.11 +++ distinfo 15 Oct 2017 08:14:35 -0000 @@ -1,2 +1,2 @@ -SHA256 (acpica-unix-20170303.tar.gz) = wJPJ6r0fjFHXk2TYKZdcUzXIAoxIFqeoDfuFkPMYibU= -SIZE (acpica-unix-20170303.tar.gz) = 1710577 +SHA256 (acpica-unix-20170929.tar.gz) = x4aGiubHpMe8oZpcpmv7FnQMrVwcAbIWQpMvLw3qnMg= +SIZE (acpica-unix-20170929.tar.gz) = 1763050 Index: patches/patch-generate_unix_Makefile_config =================================================================== RCS file: /cvs/ports/devel/acpica/patches/patch-generate_unix_Makefile_config,v retrieving revision 1.6 diff -u -p -r1.6 patch-generate_unix_Makefile_config --- patches/patch-generate_unix_Makefile_config 18 Mar 2017 21:37:55 -0000 1.6 +++ patches/patch-generate_unix_Makefile_config 15 Oct 2017 08:14:35 -0000 @@ -1,7 +1,8 @@ $OpenBSD: patch-generate_unix_Makefile_config,v 1.6 2017/03/18 21:37:55 sthen Exp $ ---- generate/unix/Makefile.config.orig Fri Mar 3 17:25:48 2017 -+++ generate/unix/Makefile.config Sat Mar 18 21:30:14 2017 -@@ -194,7 +194,6 @@ CWARNINGFLAGS = \ +Index: generate/unix/Makefile.config +--- generate/unix/Makefile.config.orig ++++ generate/unix/Makefile.config +@@ -196,7 +196,6 @@ CWARNINGFLAGS = \ -Wall\ -Wbad-function-cast\ -Wdeclaration-after-statement\ @@ -9,7 +10,7 @@ $OpenBSD: patch-generate_unix_Makefile_c -Wformat=2\ -Wmissing-declarations\ -Wmissing-prototypes\ -@@ -216,24 +215,7 @@ CWARNINGFLAGS += \ +@@ -218,24 +217,7 @@ CWARNINGFLAGS += \ -Wmissing-field-initializers\ -Wnested-externs\ -Wold-style-definition\ Index: patches/patch-generate_unix_acpiexec_Makefile =================================================================== RCS file: /cvs/ports/devel/acpica/patches/patch-generate_unix_acpiexec_Makefile,v retrieving revision 1.10 diff -u -p -r1.10 patch-generate_unix_acpiexec_Makefile --- patches/patch-generate_unix_acpiexec_Makefile 18 Mar 2017 21:37:55 -0000 1.10 +++ patches/patch-generate_unix_acpiexec_Makefile 15 Oct 2017 08:14:35 -0000 @@ -1,7 +1,8 @@ $OpenBSD: patch-generate_unix_acpiexec_Makefile,v 1.10 2017/03/18 21:37:55 sthen Exp $ ---- generate/unix/acpiexec/Makefile.orig Fri Mar 3 17:25:48 2017 -+++ generate/unix/acpiexec/Makefile Sat Mar 18 21:30:14 2017 -@@ -251,12 +251,6 @@ ifneq ($(HOST),_QNX) +Index: generate/unix/acpiexec/Makefile +--- generate/unix/acpiexec/Makefile.orig ++++ generate/unix/acpiexec/Makefile +@@ -256,12 +256,6 @@ ifneq ($(HOST),_QNX) LDFLAGS += -lpthread endif