Overview

This is protobuf-c, a C implementation of the Google Protocol Buffers data serialization format. It includes libprotobuf-c, a pure C library that implements protobuf encoding and decoding, and protoc-c, a code generator that converts Protocol Buffer .proto files to C descriptor code, based on the original protoc. protobuf-c formerly included an RPC implementation; that code has been split out into the protobuf-c-rpc project.

protobuf-c was originally written by Dave Benson and maintained by him through version 0.15 but is now being maintained by a new team. Thanks, Dave!

Mailing list

protobuf-c's mailing list is hosted on a Google Groups forum. Subscribe by sending an email to protobuf-c+subscribe@googlegroups.com.

Building

protobuf-c requires a C compiler, a C++ compiler, protobuf, and pkg-config to be installed.

./configure && make && make install

If building from a git checkout, the autotools (autoconf, automake, libtool) must also be installed, and the build system must be generated by running the autogen.sh script.

./autogen.sh && ./configure && make && make install

Synopsis

Use the protoc-c command to generate .pb-c.c and .pb-c.h output files from your .proto input file.

protoc-c --c_out=. example.proto

Include the .pb-c.h file from your C source code.

#include "example.pb-c.h"

Compile your C source code together with the .pb-c.c file. Add the output of the following command to your compile flags.

pkg-config --cflags 'libprotobuf-c >= 1.0.0'

Link against the libprotobuf-c support library. Add the output of the following command to your link flags.

pkg-config --libs 'libprotobuf-c >= 1.0.0'

If using autotools, the PKG_CHECK_MODULES macro can be used to detect the presence of libprotobuf-c. Add the following line to your configure.ac file:

PKG_CHECK_MODULES([PROTOBUF_C], [libprotobuf-c >= 1.0.0])

This will place compiler flags in the PROTOBUF_C_CFLAGS variable and linker flags in the PROTOBUF_C_LDFLAGS variable. Read more information here about the PKG_CHECK_MODULES macro.

Versioning

protobuf-c follows the Semantic Versioning Specification as of version 1.0.0.

Note that as of version of 1.0.0, the header files generated by the protoc-c compiler contain version guards to prevent incompatibilities due to version skew between the .pb-c.h files generated by protoc-c and the public protobuf-c.h include file supplied by the libprotobuf-c support library. While we will try not to make changes to protobuf-c that will require triggering the version guard often, such as releasing a new major version of protobuf-c, this cannot be guaranteed. Thus, it's a good idea to recompile your .pb-c.c and .pb-c.h files from their source .proto files with protoc-c as part of your build system, with proper source file dependency tracking, rather than shipping potentially stale .pb-c.c and .pb-c.h files that may not be compatible with the libprotobuf-c headers installed on the system in project artifacts like repositories and release tarballs. (Note that the output of the protoc-c code generator is not standalone, as the output of some other tools that generate C code is, such as flex and bison.)

Major API/ABI changes may occur between major version releases, by definition. It is not recommended to export the symbols in the code generated by protoc-c in a stable library interface, as this will embed the protobuf-c ABI into your library's ABI. Nor is it recommended to install generated .pb-c.h files into a public header file include path as part of a library API, as this will tie clients of your library's API to particular versions of libprotobuf-c.

Contributing

Please send patches to the protobuf-c mailing list or by opening a GitHub pull request.

Copyright to all contributions are retained by the original author, but must be licensed under the terms of the BSD-2-Clause license. Please add a Signed-off-by header to your commit message (git commit -s) to indicate that you are licensing your contribution under these terms.