Add more explanations

diff --git a/cmake/configure/configure_2_boost.cmake b/cmake/configure/configure_2_boost.cmake
index aa78f31475c067520ede2e94b1273778657077e9..bb5640bfd8337e06c4845c518299a25001462012 100644 (file)
--- a/cmake/configure/configure_2_boost.cmake
+++ b/cmake/configure/configure_2_boost.cmake
@@ -63,8 +63,14 @@ MACRO(FEATURE_BOOST_CONFIGURE_COMMON)
   ELSE()
     ADD_FLAGS(CMAKE_REQUIRED_FLAGS "-Werror")
   ENDIF()
+  # The configure function is called only once. In case an externally provided
+  # boost library is detected, BOOST_INCLUDE_DIRS contains the include paths to
+  # be used and BOOST_BUNDLED_INCLUDE_DIRS is empty. For the bundled library, it
+  # is the other way around.
   LIST(APPEND CMAKE_REQUIRED_INCLUDES ${BOOST_INCLUDE_DIRS} ${BOOST_BUNDLED_INCLUDE_DIRS})
 
+  # In case, the boost library already sets BOOST_NO_AUTO_PTR we report
+  # DEAL_II_HAS_AUTO_PTR to be true to avoid redefining the macro.
   CHECK_CXX_SOURCE_COMPILES(
     "
     #include <memory>
@@ -104,6 +110,8 @@ MACRO(FEATURE_BOOST_CONFIGURE_BUNDLED)
     ENDIF()
   ENDIF()
 
+  # We need to set this path before calling the configure function
+  # to be able to use the include paths in the checks.
   SET(BOOST_BUNDLED_INCLUDE_DIRS ${BOOST_FOLDER}/include)
 
   FEATURE_BOOST_CONFIGURE_COMMON()