1 files changed, 49 insertions, 2 deletions
diff --git a/cmake/examples.cmake b/cmake/examples.cmake
index f7d4d601..5a2538e4 100644
--- a/cmake/examples.cmake
+++ b/cmake/examples.cmake
@@ -2,9 +2,56 @@ if(protobuf_VERBOSE)
   message(STATUS "Protocol Buffers Examples Configuring...")
 endif()
 
-# Add examples subproject
-add_subdirectory(../examples examples)
+get_filename_component(examples_dir "../examples" ABSOLUTE)
 
 if(protobuf_VERBOSE)
   message(STATUS "Protocol Buffers Examples Configuring done")
 endif()
+include(ExternalProject)
+
+# Internal utility function: Create a custom target representing a build of examples with custom options.
+function(add_examples_build NAME)
+  ExternalProject_Add(${NAME}
+    PREFIX ${NAME}
+    SOURCE_DIR "${examples_dir}"
+    BINARY_DIR ${NAME}
+    STAMP_DIR ${NAME}/logs
+    INSTALL_COMMAND "" #Skip
+    LOG_CONFIGURE 1
+    CMAKE_CACHE_ARGS "-Dprotobuf_MSVC_STATIC_RUNTIME:BOOL=${protobuf_MSVC_STATIC_RUNTIME}"
+                     "-DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}"
+                     "-Dprotobuf_VERBOSE:BOOL=${protobuf_VERBOSE}"
+                     ${ARGN}
+  )
+  set_property(TARGET ${NAME} PROPERTY FOLDER "Examples")
+  set_property(TARGET ${NAME} PROPERTY EXCLUDE_FROM_ALL TRUE)
+endfunction()
+
+# Add examples as an external project.
+# sub_directory cannot be used because the find_package(protobuf) call would cause failures with redefined targets.
+add_examples_build(examples "-Dprotobuf_DIR:PATH=${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_CMAKEDIR}")
+add_dependencies(examples libprotobuf protoc)
+
+option(protobuf_BUILD_EXAMPLES_MULTITEST "Build Examples in multiple configurations. Useful for testing." OFF)
+mark_as_advanced(protobuf_BUILD_EXAMPLES_MULTITEST)
+if(protobuf_BUILD_EXAMPLES_MULTITEST)
+  set_property(GLOBAL PROPERTY USE_FOLDERS ON)
+
+  #Build using the legacy compatiblity module.
+  add_examples_build(examples-legacy
+    "-Dprotobuf_DIR:PATH=${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_CMAKEDIR}"
+    "-Dprotobuf_MODULE_COMPATIBLE:BOOL=TRUE"
+  )
+  add_dependencies(examples-legacy libprotobuf protoc)
+
+  #Build using the installed library.
+  add_examples_build(examples-installed
+    "-Dprotobuf_DIR:PATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_CMAKEDIR}"
+  )
+
+  #Build using the installed library in legacy compatiblity mode.
+  add_examples_build(examples-installed-legacy
+    "-Dprotobuf_DIR:PATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_CMAKEDIR}"
+    "-Dprotobuf_MODULE_COMPATIBLE:BOOL=TRUE"
+  )
+endif()