CMake: Add a compatibility check for taskflow-3.0 onwards

diff --git a/cmake/configure/configure_1_taskflow.cmake b/cmake/configure/configure_1_taskflow.cmake
index d4ed1d561bed8cb67f74da7db27bc56fdcc3aebf..1951a41a326e9d0c0905349e6af2c77a5e4db0ba 100644 (file)
--- a/cmake/configure/configure_1_taskflow.cmake
+++ b/cmake/configure/configure_1_taskflow.cmake
@@ -42,6 +42,26 @@ MACRO(FEATURE_TASKFLOW_FIND_EXTERNAL var)
       )
     SET(${var} FALSE)
   ENDIF()
+
+
+  IF(NOT TASKFLOW_VERSION VERSION_LESS "3.0" AND NOT DEAL_II_HAVE_CXX17)
+    # Clear the previously determined version numbers to avoid confusion
+    SET(TASKFLOW_VERSION "bundled")
+    SET(TASKFLOW_VERSION_MAJOR "")
+    SET(TASKFLOW_VERSION_MINOR "")
+
+    MESSAGE(STATUS
+      "The externally provided Taskflow library (version 3.0 onwards)
+      requires C++17 support, which has not been configured."
+      )
+    SET(TASKFLOW_ADDITIONAL_ERROR_STRING
+      "The externally provided Taskflow library (version 3.0 onwards) "
+      "requires C++17 support, but no C++17 support had been detected "
+      "during configuration.\n"
+      "Try to set -DDEAL_II_CXX_FLAGS=\"-std=c++17\" by hand.\n"
+      )
+    SET(${var} FALSE)
+  ENDIF()
 ENDMACRO()