CMake: fix compilation with bundled boost and modern clang

std::unary_function has been removed in C++17. Fix compilation with
clang and other compiles that enforce strict standard compliance by
exporting BOOST_NO_CXX98_FUNCTION_BASE,

https://github.com/boostorg/config/pull/430

diff --git a/bundled/setup_bundled.cmake b/bundled/setup_bundled.cmake
index 944ebd8d94aee29f2115679f46a1efc0d8edbea0..0027cde4f1cc46c2ec7c578f555a24758face57b 100644 (file)
--- a/bundled/setup_bundled.cmake
+++ b/bundled/setup_bundled.cmake
@@ -57,6 +57,16 @@ macro(feature_boost_configure_bundled)
     list(APPEND DEAL_II_DEFINITIONS "BOOST_ALL_NO_LIB")
   endif()
 
+  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    #
+    # std::unary_function has been removed in C++17. Fix compilation with
+    # clang (that enforces strict standard compliance) by exporting
+    # BOOST_NO_CXX98_FUNCTION_BASE,
+    # https://github.com/boostorg/config/pull/430
+    #
+    list(APPEND DEAL_II_DEFINITIONS "BOOST_NO_CXX98_FUNCTION_BASE")
+  endif()
+
   enable_if_supported(DEAL_II_WARNING_FLAGS "-Wno-unused-local-typedefs")
   enable_if_supported(DEAL_II_WARNING_FLAGS "-Wno-parentheses")