Update third_party protobuf to v3.6.1

Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/16251

Reviewed By: ezyang

Differential Revision: D13781444

Pulled By: bddppq

fbshipit-source-id: b713a021033d214f30a49ee02b95edf8633bcc50

cmake/ProtoBuf.cmake

@@ -63,7 +63,12 @@ macro(custom_protobuf_find)
   if (NOT TARGET protobuf::libprotobuf)
     add_library(protobuf::libprotobuf ALIAS libprotobuf)
     add_library(protobuf::libprotobuf-lite ALIAS libprotobuf-lite)
-    add_executable(protobuf::protoc ALIAS protoc)
+    # There is link error when cross compiling protoc on mobile:
+    # https://github.com/protocolbuffers/protobuf/issues/2719
+    # And protoc is very unlikely needed for mobile builds.
+    if (NOT (ANDROID OR IOS))
+      add_executable(protobuf::protoc ALIAS protoc)
+    endif()
   endif()
 endmacro()
 
@@ -78,17 +83,13 @@ if (ANDROID OR IOS)
         "change in the future, and you will need to specify "
         "-DBUILD_CUSTOM_PROTOBUF=ON explicitly.")
   endif()
+  # There is link error when cross compiling protoc on mobile:
+  # https://github.com/protocolbuffers/protobuf/issues/2719
+  # And protoc is very unlikely needed for mobile builds.
+  set(__caffe2_protobuf_BUILD_PROTOC_BINARIES ${protobuf_BUILD_PROTOC_BINARIES})
+  set(protobuf_BUILD_PROTOC_BINARIES OFF CACHE BOOL "" FORCE)
   custom_protobuf_find()
-  # Unfortunately, new protobuf does not support libprotoc and protoc
-  # cross-compilation so we will need to exclude it.
-  # The problem of using EXCLUDE_FROM_ALL is that one is not going to be able
-  # to run cmake install. A proper solution has to be implemented by protobuf
-  # since we derive our cmake files from there.
-  # TODO(jiayq): change this once https://github.com/google/protobuf/pull/3878
-  # merges.
-  set_target_properties(
-      libprotoc protoc PROPERTIES
-      EXCLUDE_FROM_ALL 1 EXCLUDE_FROM_DEFAULT_BUILD 1)
+  set(protobuf_BUILD_PROTOC_BINARIES ${__caffe2_protobuf_BUILD_PROTOC_BINARIES} CACHE BOOL "" FORCE)
 elseif (BUILD_CUSTOM_PROTOBUF)
   message(STATUS "Building using own protobuf under third_party per request.")
   custom_protobuf_find()

cmake/ProtoBufPatch.cmake

@@ -18,6 +18,16 @@ string(
   content
   "${content}")
 
+# https://github.com/protocolbuffers/protobuf/commit/0400cca3236de1ca303af38bf81eab332d042b7c
+# changes PROTOBUF_CONSTEXPR to constexpr, which breaks windows
+# build.
+string(
+  REPLACE
+  "static constexpr int kIndexInFileMessages ="
+  "static int const kIndexInFileMessages ="
+  content
+  "${content}")
+
 foreach(ns ${NAMESPACES})
   # Insert "const ::std::string& GetEmptyStringAlreadyInited();" within
   # the namespace and make sure we only do it once in the file. Unfortunately