add tests whether simple examples for coupling to the LAMMPS library can run

examples/COUPLE/simple/CMakeLists.txt

@@ -1,17 +1,44 @@
 cmake_minimum_required(VERSION 3.10)
-project(simple CXX)
 
-set(LAMMPS_SRC_DIRECTORY "" CACHE PATH "Path for lammps source")
-if(NOT LAMMPS_SRC_DIRECTORY STREQUAL "" AND EXISTS ${LAMMPS_SRC_DIRECTORY}/cmake/CMakeLists.txt)
-  option(BUILD_LIB "Build LAMMPS library" ON)
-  add_subdirectory(${LAMMPS_SRC_DIRECTORY}/cmake lammps)
-else()
+# enforce out-of-source build
+if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
+  message(FATAL_ERROR "In-source builds are not allowed. You must create and use a build directory. "
+    "Please remove CMakeCache.txt and CMakeFiles first.")
+endif()
+
+project(couple-simple VERSION 1.0 LANGUAGES C CXX)
+
+# by default, install into $HOME/.local (not /usr/local),
+# so that no root access (and sudo) is needed
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+   set(CMAKE_INSTALL_PREFIX "$ENV{HOME}/.local" CACHE PATH "Default install path" FORCE)
+endif()
+
+# ugly hacks for MSVC which by default always reports an old C++ standard in the __cplusplus macro
+# and prints lots of pointless warnings about "unsafe" functions
+if(MSVC)
+  if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+    if(LAMMPS_EXCEPTIONS)
+      add_compile_options(/EHsc)
+    endif()
+  endif()
+  add_compile_definitions(_CRT_SECURE_NO_WARNINGS)
+endif()
+
+find_package(MPI QUIET)
+# do not include the (obsolete) MPI C++ bindings which makes
+# for leaner object files and avoids namespace conflicts
+set(MPI_CXX_SKIP_MPICXX TRUE)
+
+##########################
+
+# build within LAMMPS build system
+if(NOT LAMMPS_SOURCE_DIR)
   find_package(LAMMPS REQUIRED)
 endif()
 
 add_executable(simpleCC simple.cpp)
 target_link_libraries(simpleCC LAMMPS::lammps)
 
-enable_language(C)
 add_executable(simpleC simple.c)
 target_link_libraries(simpleC LAMMPS::lammps)