Updating binaries other than the Linux 64-bit and MinGW ones

1. Go to http://search.maven.org/
2. Search for g:“com.google.protobuf”
3. Download the “jar” link from protobuf-java and put them in <Bazel tree>/third_party/protobuf/<version>
4. Download all binaries from “protoc” and put them in <Bazel tree>/third_party/protobuf/<version>
5. Set executable bit: chmod +x *.exe

Updating the Linux 64-bit proto compiler

The 64-bit Linux version of the proto compiler is linked statically. To update it, do the following steps on an x86_64 machine:

1. git clone http://github.com/google/protobuf.git
2. git checkout <tag or commithash> (e.g. v3.0.0 or e8ae137)
3. ./autogen.sh
4. LDFLAGS=-static ./configure
5. Change LDFLAGS = -static to LDFLAGS = -all-static in src/Makefile.
6. make
7. cp src/protoc <Bazel tree>/third_party/protobuf/<version>/protoc-<version>-linux-x86_64.exe .

Updating the MinGW proto compiler (64-bit)

Do this from a MinGW shell ([https://sourceforge.net/projects/msys2/files/]) on a Windows machine.

1. Clone the protobuf repo and check out the right commit

   git clone http://github.com/google/protobuf.git
   git checkout <tag or commithash>   # e.g. `v3.0.0` or `e8ae137`
   

2. Close all other MSYS/MinGW/Cygwin windows. Kill all running background jobs. This step is optional, but if you have other terminal windows open the next step may print some error messages (though it still seems to work).

3. Install necessary MinGW packages

   pacman -Syuu autoconf automake libtool curl make gcc unzip
   

4. Configure for static linking and build like you would for Unix

   ./autogen.sh
   ./configure --disable-shared   # takes about 2 minutes
   ./make                         # takes about 11 minutes
   

5. Copy resulting binary

   cp src/protoc.exe <bazel tree>/third_party/protobuf/protoc-mingw.exe
   

Updating the Linux s390x 64-bit proto compiler

To add 64-bit Linux s390x version of the statically linked proto compiler, use below steps:

1. Build Protobuf compiler (v3.0.0-beta-2) from https://github.com/google/protobuf.
2. cp src/protoc <Bazel tree>/third_party/protobuf/protoc-linux-s390x_64.exe
3. cp src/protoc <Bazel tree>/third_party/protobuf/<version>/protoc-linux-s390x_64.exe

Updating protobuf.bzl and the src/ directory:

1. git clone http://github.com/google/protobuf.git
2. git checkout <tag or commithash> (e.g. v3.0.0 or e8ae137)
3. mkdir -p third_party/protobuf/<version>/src/google in the root of the Bazel tree.
4. cp -R <root of protobuf tree>/src/google/protobuf third_party/protobuf/src/google
5. Update the rules in third_party/protobuf/BUILD with the rules in the protobuf repository.

Finally, update the rules:

1. Add a BUILD file to third_party/protobuf/<version>/. Use the BUILD file for the previous version as a template. Update the cc_library rules to match the rules in the BUILD file in the protobuf repository. Also copy protobuf.bzl from the protobuf repository into third_party/protobuf/<version>/.
2. Modify third_party/protobuf/BUILD to point to the new rules.
3. Delete the old version of protobuf.

Updating anything else in the directory

Follow usual procedure as described on https://www.bazel.build/contributing.html