1 files changed, 81 insertions, 12 deletions
diff --git a/cmake/external/protobuf.cmake b/cmake/external/protobuf.cmake
index 21cfac3..66d1426 100644
--- a/cmake/external/protobuf.cmake
+++ b/cmake/external/protobuf.cmake
@@ -14,28 +14,97 @@
 
 include(ExternalProject)
 
+# Protubuf has CMake support, but includes it in a `cmake` subdirectory, which
+# does not work with CMake's ExternalProject by default. CMake 3.7 added
+# SOURCE_SUBDIR as a means of supporting this but that's too new to require
+# yet.
+
+# Compose CMAKE_ARGS
+set(
+  cmake_args
+  -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
+  -DBUILD_SHARED_LIBS:BOOL=OFF
+  -Dprotobuf_BUILD_TESTS:BOOL=OFF
+  -Dprotobuf_WITH_ZLIB:BOOL=OFF
+  -Dprotobuf_MSVC_STATIC_RUNTIME:BOOL=ON
+)
+
+# For single-configuration generators, pass CONFIG at configure time
+if(NOT CMAKE_CONFIGURATION_TYPES)
+  list(APPEND cmake_args -DCMAKE_BUILD_TYPE=$<CONFIG>)
+endif()
+
+
+if(CMAKE_VERSION VERSION_LESS "3.7")
+  # Manually compose the commands required to invoke CMake in the external
+  # project.
+  #
+  # Compose CONFIGURE_COMMAND so as to preserve the outer CMake's generator
+  # configuration in the sub-build. Without this the builds can invoke
+  # different compilers or disagree about word size or other fundamental
+  # parameters making the output of the sub-build useless. This is based on
+  # _ep_extract_configure_command in ExternalProject.cmake.
+  set(configure "${CMAKE_COMMAND}")
+
+  if(CMAKE_EXTRA_GENERATOR)
+    list(APPEND configure "-G${CMAKE_EXTRA_GENERATOR} - ${CMAKE_GENERATOR}")
+  else()
+    list(APPEND configure "-G${CMAKE_GENERATOR}")
+  endif()
+
+  if(CMAKE_GENERATOR_PLATFORM)
+    list(APPEND configure "-A${CMAKE_GENERATOR_PLATFORM}")
+  endif()
+
+  if(CMAKE_GENERATOR_TOOLSET)
+    list(APPEND configure "-T${CMAKE_GENERATOR_TOOLSET}")
+  endif()
+
+  list(
+    APPEND configure
+    ${cmake_args}
+    "${PROJECT_BINARY_DIR}/external/protobuf/src/protobuf/cmake"
+  )
+
+  # Compose BUILD_COMMAND and INSTALL_COMMAND
+  set(build "${CMAKE_COMMAND}" --build .)
+
+  # For multi-configuration generators, pass CONFIG at build time.
+  if(CMAKE_CONFIGURATION_TYPES)
+    list(APPEND build --config $<CONFIG>)
+  endif()
+
+  set(install ${build} --target install)
+
+  set(
+    commands
+    CONFIGURE_COMMAND ${configure}
+    BUILD_COMMAND ${build}
+    INSTALL_COMMAND ${install}
+  )
+
+else()
+  # CMake 3.7 and above support this directly.
+  set(
+    commands
+    CMAKE_ARGS ${cmake_args}
+    SOURCE_SUBDIR cmake
+  )
+endif()
+
 ExternalProject_Add(
   protobuf
 
   DOWNLOAD_DIR ${FIREBASE_DOWNLOAD_DIR}
-  DOWNLOAD_NAME protobuf-v3.5.11.tar.gz
+  DOWNLOAD_NAME protobuf-v3.5.1.1.tar.gz
   URL https://github.com/google/protobuf/archive/v3.5.1.1.tar.gz
   URL_HASH SHA256=56b5d9e1ab2bf4f5736c4cfba9f4981fbc6976246721e7ded5602fbaee6d6869
 
   PREFIX ${PROJECT_BINARY_DIR}/external/protobuf
+  INSTALL_DIR ${FIREBASE_INSTALL_DIR}
 
-  # protobuf ships CMake files but not at the root of the repo, which confuses
-  # CMake by default. Unfortunately when you override CONFIGURE_COMMAND like
-  # this, CMake no longer automatically plumbs in CMAKE_ARGS and friends so
-  # those need to be manually passed in this command line.
-  CONFIGURE_COMMAND
-    ${CMAKE_COMMAND}
-      -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}
-      -DCMAKE_INSTALL_PREFIX:PATH=${FIREBASE_INSTALL_DIR}
-      -Dprotobuf_BUILD_TESTS=OFF
-      ${PROJECT_BINARY_DIR}/external/protobuf/src/protobuf/cmake
+  ${commands}
 
   UPDATE_COMMAND ""
   TEST_COMMAND ""
-  INSTALL_COMMAND ""
 )