Protobuf vendoring and generated code

Protocol Buffers (protobuf) source is available at:

https://github.com/protocolbuffers/protobuf

This code is covered under the BSD license (see LICENSE). Documentation is available at https://developers.google.com/protocol-buffers/.

The tree's current version of the protobuf library is 35.0.

We do not include the protobuf tests or the protoc compiler.

Upgrading the protobuf library

WARNING: The vendoring process may download and execute untrusted code from the protobuf repository. Only vendor releases from trusted sources and review the vendored content carefully.

Decide the protobuf release version you want to vendor (for example, v35.0).
From the Gecko top source directory, use the standard moz.yaml vendoring workflow to re-vendor protobuf. Options are documented in toolkit/components/protobuf/moz.yaml. See also the Firefox build docs for common vendoring operations: [Common vendoring operations] (https://firefox-source-docs.mozilla.org/mozbuild/vendor/index.html#common-vendoring-operations)

Run:

mach vendor toolkit/components/protobuf/moz.yaml -r v35.0 --patch-mode none

and then apply local patches:

mach vendor toolkit/components/protobuf/moz.yaml --patch-mode only

Where -r v35.0 specifies the protobuf version.

Vendoring automatically regenerates all .pb.cc and .pb.h files specified in scripts/generate_files.py.

Update the moz.build to export the new set of headers and add any new .cc files to the unified sources and remove old ones. Note that we only need:
- files contained in the libprotobuf_lite_srcs target (file_lists.cmake)
- the header files they need
- gzip streams (for devtools)

Adding or updating generated C++ files

When a .proto source file is added, moved, or otherwise changed, update scripts/generate_files.py so the generated C++ files are produced in the correct location with the right include paths.

Edit scripts/generate_files.py and add or adjust a run_protoc(...) entry for the affected .proto file(s). Set cpp_out to the directory where the generated files should live, and includes to directories that contain the .proto sources (paths are relative to the top source dir).
Regenerate the files using:

   mach python toolkit/components/protobuf/scripts/generate_files.py

If new generated files appear in a directory that is not already listing them, update the corresponding moz.build in that directory to include the new files.