# Protocol Buffers - Google's data interchange format

Copyright 2008 Google Inc.

https://developers.google.com/protocol-buffers/

## C++ Installation - Unix

If you get the source from github, you need to generate the configure script first:

    $ ./autogen.sh

This will download gtest source (which is used for C++ Protocol Buffer unit-tests) to the current directory and run automake, autoconf, etc. to generate the configure script and various template makefiles.

You can skip this step if you are using a release package (which already contains gtest and the configure script).

To build and install the C++ Protocol Buffer runtime and the Protocol Buffer compiler (protoc) execute the following:

    $ ./configure
    $ make
    $ make check
    $ make install

If "make check" fails, you can still install, but it is likely that some features of this library will not work correctly on your system. Proceed at your own risk.

"make install" may require superuser privileges.

For advanced usage information on configure and make, see INSTALL.txt.

Hint on install location

By default, the package will be installed to /usr/local. However, on many platforms, /usr/local/lib is not part of LD_LIBRARY_PATH. You can add it, but it may be easier to just install to /usr instead. To do this, invoke configure as follows:

    ./configure --prefix=/usr

If you already built the package with a different prefix, make sure to run "make clean" before building again.

Compiling dependent packages

To compile a package that uses Protocol Buffers, you need to pass various flags to your compiler and linker. As of version 2.2.0, Protocol Buffers integrates with pkg-config to manage this. If you have pkg-config installed, then you can invoke it to get a list of flags like so:

    pkg-config --cflags protobuf         # print compiler flags
    pkg-config --libs protobuf           # print linker flags
    pkg-config --cflags --libs protobuf  # print both

For example:

    c++ my_program.cc my_proto.pb.cc `pkg-config --cflags --libs protobuf`

Note that packages written prior to the 2.2.0 release of Protocol Buffers may not yet integrate with pkg-config to get flags, and may not pass the correct set of flags to correctly link against libprotobuf. If the package in question uses autoconf, you can often fix the problem by invoking its configure script like:

    configure CXXFLAGS="$(pkg-config --cflags protobuf)" \
              LIBS="$(pkg-config --libs protobuf)"

This will force it to use the correct flags.

If you are writing an autoconf-based package that uses Protocol Buffers, you should probably use the PKG_CHECK_MODULES macro in your configure script like:

    PKG_CHECK_MODULES([protobuf], [protobuf])

See the pkg-config man page for more info.

If you only want protobuf-lite, substitute "protobuf-lite" in place of "protobuf" in these examples.

Note for cross-compiling

The makefiles normally invoke the protoc executable that they just built in order to build tests. When cross-compiling, the protoc executable may not be executable on the host machine. In this case, you must build a copy of protoc for the host machine first, then use the --with-protoc option to tell configure to use it instead. For example:

    ./configure --with-protoc=protoc

This will use the installed protoc (found in your $PATH) instead of trying to execute the one built during the build process. You can also use an executable that hasn't been installed. For example, if you built the protobuf package for your host machine in ../host, you might do:

    ./configure --with-protoc=../host/src/protoc

Either way, you must make sure that the protoc executable you use has the same version as the protobuf source code you are trying to use it with.

Note for Solaris users

Solaris 10 x86 has a bug that will make linking fail, complaining about libstdc++.la being invalid. We have included a work-around in this package. To use the work-around, run configure as follows:

    ./configure LDFLAGS=-L$PWD/src/solaris

See src/solaris/libstdc++.la for more info on this bug.

Note for HP C++ Tru64 users

To compile invoke configure as follows:

    ./configure CXXFLAGS="-O -std ansi -ieee -D__USE_STD_IOSTREAM"

Also, you will need to use gmake instead of make.

## C++ Installation - Windows

If you are using Microsoft Visual C++, see vsprojects/readme.txt.

If you are using Cygwin or MinGW, follow the Unix installation instructions, above.

## Binary Compatibility Warning

Due to the nature of C++, it is unlikely that any two versions of the Protocol Buffers C++ runtime libraries will have compatible ABIs. That is, if you linked an executable against an older version of libprotobuf, it is unlikely to work with a newer version without re-compiling. This problem, when it occurs, will normally be detected immediately on startup of your app. Still, you may want to consider using static linkage. You can configure this package to install static libraries only using:

    ./configure --disable-shared

## Java and Python Installation

The Java and Python runtime libraries for Protocol Buffers are located in the java and python directories. See the README file in each directory for more information on how to compile and install them. Note that both of them require you to first install the Protocol Buffer compiler (protoc), which is part of the C++ package.

## Usage

The complete documentation for Protocol Buffers is available via the web at:

    https://developers.google.com/protocol-buffers/