Fix cmake requirements.

diff --git a/examples/step-86/CMakeLists.txt b/examples/step-86/CMakeLists.txt
index 209c9a0d5ef40b3535d5a47d5f2e24bee54bd99d..acf8b260fe61d6b8d3ce8e42a1e646cff53ae815 100644 (file)
--- a/examples/step-86/CMakeLists.txt
+++ b/examples/step-86/CMakeLists.txt
@@ -34,6 +34,21 @@ if(NOT ${deal.II_FOUND})
     )
 endif()
 
+#
+# Are all dependencies fulfilled?
+#
+if(NOT DEAL_II_WITH_PETSC OR DEAL_II_PETSC_WITH_COMPLEX) # keep in one line
+  message(FATAL_ERROR "
+Error! This tutorial requires a deal.II library that was configured with the following options:
+    DEAL_II_WITH_PETSC = ON
+    DEAL_II_PETSC_WITH_COMPLEX = OFF
+However, the deal.II library found at ${DEAL_II_PATH} was configured with these options:
+    DEAL_II_WITH_PETSC = ${DEAL_II_WITH_PETSC}
+    DEAL_II_PETSC_WITH_COMPLEX = ${DEAL_II_PETSC_WITH_COMPLEX}
+This conflicts with the requirements."
+    )
+endif()
+
 deal_ii_initialize_cached_variables()
 project(${TARGET})
 deal_ii_invoke_autopilot()