Merge pull request #189 from thelfer/187-add-a-message-stating-that-the-dependency-to-tbb-can-be-removed-if-parallel-stl-is-disabled-when-compiling-with-libstdc

Fix Issue #187

Author: thelfer

cmake/modules/clang.cmake

@@ -83,7 +83,10 @@ if(enable-parallel-stl-algorithms)
  # This is a poor test to check of libstc++ is used
  if(UNIX AND NOT APPLE)
    if(NOT enable-libcxx)
-     find_package(TBB REQUIRED)
+     find_package(TBB)
+     if(NOT TBB_FOUND)
+       message(FATAL_ERROR "Intel Threading Building Blocks library (TBB) is required by libstdc++ to support parallel STL algorithms. You may want to disable support for those parallel algorithms by passing -Denable-parallel-stl-algorithms=OFF to cmake")
+     endif(NOT TBB_FOUND)
      list(APPEND MGIS_REQUIRED_ADDITIONAL_PACKAGES "TBB")
      list(APPEND MGIS_ADDITIONAL_LIBRARIES "TBB::tbb")
    endif(NOT enable-libcxx)

cmake/modules/gcc.cmake

@@ -111,7 +111,10 @@ endif(enable-sanitize-options)
 set(COMPILER_C_WARNINGS "-Wall -W -pedantic")
 
 if(enable-parallel-stl-algorithms)
-  find_package(TBB REQUIRED)
+  find_package(TBB)
+  if(NOT TBB_FOUND)
+     message(FATAL_ERROR "Intel Threading Building Blocks library (TBB) is required by libstdc++ to support parallel STL algorithms. You may want to disable support for those parallel algorithms by passing -Denable-parallel-stl-algorithms=OFF to cmake")
+  endif(NOT TBB_FOUND)
   list(APPEND MGIS_REQUIRED_ADDITIONAL_PACKAGES "TBB")
   list(APPEND MGIS_ADDITIONAL_LIBRARIES "TBB::tbb")
 endif(enable-parallel-stl-algorithms)