Index: head/science/vipster/Makefile
===================================================================
--- head/science/vipster/Makefile	(revision 522471)
+++ head/science/vipster/Makefile	(revision 522472)
@@ -1,38 +1,45 @@
 # $FreeBSD$
 
 PORTNAME=	vipster
 DISTVERSIONPREFIX=	v
 DISTVERSION=	1.18b-75
 DISTVERSIONSUFFIX=	-gfa5853f
+PORTREVISION=	1
 CATEGORIES=	science
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	Crystalline and molecular structure visualisation program
 
 LICENSE=	GPLv3
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
-USES=		cmake compiler:c++17-lang
+USES=		cmake
 USE_GITHUB=	yes
 GH_ACCOUNT=	sgsaenger
 USE_LDCONFIG=	yes
 
 OPTIONS_DEFINE=		DESKTOP PYTHON
 OPTIONS_DEFAULT=	DESKTOP
 OPTIONS_SUB=		yes
 
 DESKTOP_DESC=		Build QT-based desktop app
 DESKTOP_CMAKE_BOOL=	DESKTOP
 DESKTOP_USES=		qt:5
 DESKTOP_USE=		QT=core,gui,widgets,buildtools_build,qmake_build
 
 PYTHON_CMAKE_BOOL=	PYTHON
 PYTHON_BROKEN=		Bundles pybind11: https://github.com/sgsaenger/vipster/issues/23
+
+# use clang from ports because older clang (clang-6) lacks the c++17 feature std::mmap::extract
+BUILD_DEPENDS+=	clang${LLVM_DEFAULT}:devel/llvm${LLVM_DEFAULT}
+CPP=		clang-cpp${LLVM_DEFAULT}
+CC=		clang${LLVM_DEFAULT}
+CXX=		clang++${LLVM_DEFAULT}
 
 do-test:
 	@cd ${BUILD_WRKSRC} && \
 		${SETENV} ${CONFIGURE_ENV} ${CMAKE_BIN} ${CMAKE_ARGS} -DTESTS:BOOL=ON ${CMAKE_SOURCE_PATH} && \
 		${SETENV} ${MAKE_ENV} ${MAKE_CMD} ${MAKE_ARGS} ${ALL_TARGET} && \
 		${SETENV} ${MAKE_ENV} ${MAKE_CMD} ${MAKE_ARGS} test
 
 .include <bsd.port.mk>