examples/cpp/helloworld/cmake_externalproject/CMakeLists.txt

# Copyright 2018 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# cmake "superbuild" file for C++ helloworld example.
# This build file demonstrates how to build the helloworld project
# and all its dependencies in a single cmake build (hence "superbuild")
# that is easy to build and maintain.
# cmake's ExternalProject_Add() is used to import all the sub-projects,
# including the "helloworld" project itself.
# See https://blog.kitware.com/cmake-superbuilds-git-submodules/

cmake_minimum_required(VERSION 2.8)

# Project
project(HelloWorld-SuperBuild C CXX)

include(ExternalProject)

# Builds c-ares project from the git submodule.
# Note: For all external projects, instead of using checked-out code, one could
# specify GIT_REPOSITORY and GIT_TAG to have cmake download the dependency directly,
# without needing to add a submodule to your project.
ExternalProject_Add(c-ares
  PREFIX c-ares
  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../../../third_party/cares/cares"
  CMAKE_CACHE_ARGS
        -DCARES_SHARED:BOOL=OFF
        -DCARES_STATIC:BOOL=ON
        -DCARES_STATIC_PIC:BOOL=ON
        -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_CURRENT_BINARY_DIR}/c-ares
)

# Builds protobuf project from the git submodule.
ExternalProject_Add(protobuf
  PREFIX protobuf
  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../../../third_party/protobuf/cmake"
  CMAKE_CACHE_ARGS
        -Dprotobuf_BUILD_TESTS:BOOL=OFF
        -Dprotobuf_WITH_ZLIB:BOOL=OFF
        -Dprotobuf_MSVC_STATIC_RUNTIME:BOOL=OFF
        -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_CURRENT_BINARY_DIR}/protobuf
)

# Builds zlib project from the git submodule.
ExternalProject_Add(zlib
  PREFIX zlib
  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../../../third_party/zlib"
  CMAKE_CACHE_ARGS
        -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_CURRENT_BINARY_DIR}/zlib
)

# the location where protobuf-config.cmake will be installed varies by platform
if (WIN32)
  set(_FINDPACKAGE_PROTOBUF_CONFIG_DIR "${CMAKE_CURRENT_BINARY_DIR}/protobuf/cmake")
else()
  set(_FINDPACKAGE_PROTOBUF_CONFIG_DIR "${CMAKE_CURRENT_BINARY_DIR}/protobuf/lib/cmake/protobuf")
endif()

# if OPENSSL_ROOT_DIR is set, propagate that hint path to the external projects with OpenSSL dependency.
set(_CMAKE_ARGS_OPENSSL_ROOT_DIR "")
if (OPENSSL_ROOT_DIR)
  set(_CMAKE_ARGS_OPENSSL_ROOT_DIR "-DOPENSSL_ROOT_DIR:PATH=${OPENSSL_ROOT_DIR}")
endif()

# Builds gRPC based on locally checked-out sources and set arguments so that all the dependencies
# are correctly located.
ExternalProject_Add(grpc
  PREFIX grpc
  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../../.."
  CMAKE_CACHE_ARGS
        -DgRPC_INSTALL:BOOL=ON
        -DgRPC_BUILD_TESTS:BOOL=OFF
        -DgRPC_PROTOBUF_PROVIDER:STRING=package
        -DgRPC_PROTOBUF_PACKAGE_TYPE:STRING=CONFIG
        -DProtobuf_DIR:PATH=${_FINDPACKAGE_PROTOBUF_CONFIG_DIR}
        -DgRPC_ZLIB_PROVIDER:STRING=package
        -DZLIB_ROOT:STRING=${CMAKE_CURRENT_BINARY_DIR}/zlib
        -DgRPC_CARES_PROVIDER:STRING=package
        -Dc-ares_DIR:PATH=${CMAKE_CURRENT_BINARY_DIR}/c-ares/lib/cmake/c-ares
        -DgRPC_SSL_PROVIDER:STRING=package
        ${_CMAKE_ARGS_OPENSSL_ROOT_DIR}
        -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_CURRENT_BINARY_DIR}/grpc
  DEPENDS c-ares protobuf zlib
)

# Build the helloworld projects itself using a CMakeLists.txt that assumes all the dependencies
# have already been installed.
# Even though helloworld is not really an "external project" from perspective of this build,
# we are still importing it using ExternalProject_Add because that allows us to use find_package()
# to locate all the dependencies (if we were building helloworld directly in this build we,
# we would have needed to manually import the libraries as opposed to reusing targets exported by
# gRPC and protobuf).
ExternalProject_Add(helloworld
  PREFIX helloworld
  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/.."
  BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/helloworld"
  INSTALL_COMMAND ""
  CMAKE_CACHE_ARGS
        -DProtobuf_DIR:PATH=${_FINDPACKAGE_PROTOBUF_CONFIG_DIR}
        -Dc-ares_DIR:PATH=${CMAKE_CURRENT_BINARY_DIR}/c-ares/lib/cmake/c-ares
        -DZLIB_ROOT:STRING=${CMAKE_CURRENT_BINARY_DIR}/zlib
        ${_CMAKE_ARGS_OPENSSL_ROOT_DIR}
        -DgRPC_DIR:PATH=${CMAKE_CURRENT_BINARY_DIR}/grpc/lib/cmake/grpc
  DEPENDS protobuf grpc
)