Merge pull request #1136 from junghans/cmake_out_source

cmake: prevent in-source build

cmake/CMakeLists.txt

@@ -69,6 +69,8 @@ get_lammps_version(${LAMMPS_SOURCE_DIR}/version.h LAMMPS_VERSION)
 # Cmake modules/macros are in a subdirectory to keep this file cleaner
 set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/Modules)
 
+include(PreventInSourceBuilds)
+
 if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CXX_FLAGS)
   #release comes with -O3 by default
   set(CMAKE_BUILD_TYPE Release CACHE STRING "Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel." FORCE)

cmake/Modules/PreventInSourceBuilds.cmake

+# - Prevent in-source builds.
+# https://stackoverflow.com/questions/1208681/with-cmake-how-would-you-disable-in-source-builds/
+
+function(prevent_in_source_builds)
+  # make sure the user doesn't play dirty with symlinks
+  get_filename_component(srcdir "${CMAKE_SOURCE_DIR}" REALPATH)
+  get_filename_component(srcdir2 "${CMAKE_SOURCE_DIR}/.." REALPATH)
+  get_filename_component(bindir "${CMAKE_BINARY_DIR}" REALPATH)
+
+  # disallow in-source builds
+  if("${srcdir}" STREQUAL "${bindir}" OR "${srcdir2}" STREQUAL "${bindir}")
+    message(FATAL_ERROR "\
+
+CMake must not to be run in the source directory. \
+Rather create a dedicated build directory and run CMake there. \
+To clean up after this aborted in-place compilation:
+  rm -r CMakeCache.txt CMakeFiles
+")
+  endif()
+endfunction()
+
+prevent_in_source_builds()