xref: /aosp_15_r20/external/protobuf/src/README.md (revision 1b3f573f81763fcece89efc2b6a5209149e44ab8)

Protocol Buffers - Google's data interchange format
===================================================

Copyright 2008 Google Inc.

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

C++ Installation - Unix
-----------------------

To build protobuf from source, the following tools are needed:

  * autoconf
  * automake
  * libtool
  * make
  * g++
  * unzip

On Ubuntu/Debian, you can install them with:

    sudo apt-get install autoconf automake libtool curl make g++ unzip

On other platforms, please use the corresponding package managing tool to
install them before proceeding.

To get the source, download one of the release .tar.gz or .zip packages in the
release page:

    https://github.com/protocolbuffers/protobuf/releases/latest

For example: if you only need C++, download `protobuf-cpp-[VERSION].tar.gz`; if
you need C++ and Java, download `protobuf-java-[VERSION].tar.gz` (every package
contains C++ source already); if you need C++ and multiple other languages,
download `protobuf-all-[VERSION].tar.gz`.

You can also get the source by "git clone" our git repository. Make sure you
have also cloned the submodules and generated the configure script (skip this
if you are using a release .tar.gz or .zip package):

    git clone https://github.com/protocolbuffers/protobuf.git
    cd protobuf
    git submodule update --init --recursive
    ./autogen.sh

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


     ./configure
     make -j$(nproc) # $(nproc) ensures it uses all cores for compilation
     make check
     sudo make install
     sudo ldconfig # refresh shared library cache.

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.

For advanced usage information on configure and make, please refer to the
autoconf documentation:

    http://www.gnu.org/software/autoconf/manual/autoconf.html#Running-configure-Scripts

**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 Mac users**

For a Mac system, Unix tools are not available by default. You will first need
to install Xcode from the Mac AppStore and then run the following command from
a terminal:

    sudo xcode-select --install

To install Unix tools, you can install "port" following the instructions at
https://www.macports.org . This will reside in /opt/local/bin/port for most
Mac installations.

    sudo /opt/local/bin/port install autoconf automake libtool

Alternative for Homebrew users:

    brew install autoconf automake libtool

Then follow the Unix instructions above.

**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.

**Note for AIX users**

Compile using the IBM xlC C++ compiler as follows:

    ./configure CXX=xlC

Also, you will need to use GNU `make` (`gmake`) instead of AIX `make`.

C++ Installation - Windows
--------------------------

If you only need the protoc binary, you can download it from the release
page:

    https://github.com/protocolbuffers/protobuf/releases/latest

In the downloads section, download the zip file protoc-$VERSION-win32.zip.
It contains the protoc binary as well as public proto files of protobuf
library.

Protobuf and its dependencies can be installed directly by using `vcpkg`:

    >vcpkg install protobuf protobuf:x64-windows

If zlib support is desired, you'll also need to install the zlib feature:

    >vcpkg install protobuf[zlib] protobuf[zlib]:x64-windows

See https://github.com/Microsoft/vcpkg for more information.

To build from source using Microsoft Visual C++, see [cmake/README.md](../cmake/README.md).

To build from source 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

Usage
-----

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

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