From 4a510960c68aafcb0ea448593cbf2a53de76fbc5 Mon Sep 17 00:00:00 2001
From: Jan Tattermusch <jtattermusch@google.com>
Date: Thu, 29 Mar 2018 14:07:20 +0200
Subject: add distribtest for grpc being added with cmake add_subdirectory

---
 examples/cpp/helloworld/CMakeLists.txt | 63 ++++++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 15 deletions(-)

(limited to 'examples/cpp')

diff --git a/examples/cpp/helloworld/CMakeLists.txt b/examples/cpp/helloworld/CMakeLists.txt
index 4f7d3fdddb..d0f705f6d9 100644
--- a/examples/cpp/helloworld/CMakeLists.txt
+++ b/examples/cpp/helloworld/CMakeLists.txt
@@ -27,22 +27,55 @@ else()
   add_definitions(-D_WIN32_WINNT=0x600)
 endif()
 
-# Find Protobuf installation
-# Looks for protobuf-config.cmake file installed by Protobuf's cmake installation.
-set(protobuf_MODULE_COMPATIBLE TRUE)
-find_package(Protobuf CONFIG REQUIRED)
-message(STATUS "Using protobuf ${protobuf_VERSION}")
+if(GRPC_AS_SUBMODULE)
+  # One way to build a projects that uses gRPC is to just include the
+  # entire gRPC project tree via "add_subdirectory".
+  # This approach is very simple to use, but the are some potential
+  # disadvantages:
+  # * it includes gRPC's CMakeLists.txt directly into your build script
+  #   without and that can make gRPC's internal setting interfere with your
+  #   own build.
+  # * depending on what's installed on your system, the contents of submodules
+  #   in gRPC's third_party/* might need to be available (and there might be
+  #   additional prerequisites required to build them). Consider using
+  #   the gRPC_*_PROVIDER options to fine-tune the expected behavior.
+  #
+  # A more robust approach to add dependency on gRPC is using
+  # cmake's ExternalProject_Add (see cmake_externalproject/CMakeLists.txt).
+  
+  # Include the gRPC's cmake build (normally grpc source code would live
+  # in a git submodule called "third_party/grpc", but this example lives in
+  # the same repository as gRPC sources, so we just look a few directories up)
+  add_subdirectory(../../.. ${CMAKE_CURRENT_BINARY_DIR}/grpc EXCLUDE_FROM_ALL)
+  message(STATUS "Using gRPC via add_subdirectory.")
+  
+  # After using add_subdirectory, we can now use the grpc targets directly from
+  # this build.
+  set(_PROTOBUF_LIBPROTOBUF libprotobuf)
+  set(_PROTOBUF_PROTOC $<TARGET_FILE:protoc>)
+  set(_GRPC_GRPCPP_UNSECURE grpc++_unsecure)
+  set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:grpc_cpp_plugin>)
+else()
+  # This branch assumes that gRPC and all its dependencies are already installed
+  # on this system, so they can be located by find_package().
+
+  # Find Protobuf installation
+  # Looks for protobuf-config.cmake file installed by Protobuf's cmake installation.
+  set(protobuf_MODULE_COMPATIBLE TRUE)
+  find_package(Protobuf CONFIG REQUIRED)
+  message(STATUS "Using protobuf ${protobuf_VERSION}")
 
-set(_PROTOBUF_LIBPROTOBUF protobuf::libprotobuf)
-set(_PROTOBUF_PROTOC $<TARGET_FILE:protobuf::protoc>)
+  set(_PROTOBUF_LIBPROTOBUF protobuf::libprotobuf)
+  set(_PROTOBUF_PROTOC $<TARGET_FILE:protobuf::protoc>)
 
-# Find gRPC installation
-# Looks for gRPCConfig.cmake file installed by gRPC's cmake installation.
-find_package(gRPC CONFIG REQUIRED)
-message(STATUS "Using gRPC ${gRPC_VERSION}")
+  # Find gRPC installation
+  # Looks for gRPCConfig.cmake file installed by gRPC's cmake installation.
+  find_package(gRPC CONFIG REQUIRED)
+  message(STATUS "Using gRPC ${gRPC_VERSION}")
 
-# gRPC C++ plugin
-set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:gRPC::grpc_cpp_plugin>)
+  set(_GRPC_GRPCPP_UNSECURE gRPC::grpc++_unsecure)
+  set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:gRPC::grpc_cpp_plugin>)
+endif()
 
 # Proto file
 get_filename_component(hw_proto "../../protos/helloworld.proto" ABSOLUTE)
@@ -74,6 +107,6 @@ foreach(_target
     ${hw_proto_srcs}
     ${hw_grpc_srcs})
   target_link_libraries(${_target}
-    ${_PROTOBUF_LIBPROTOBUF}
-    gRPC::grpc++_unsecure)
+    ${_GRPC_GRPCPP_UNSECURE}
+    ${_PROTOBUF_LIBPROTOBUF})
 endforeach()
-- 
cgit v1.2.3