[ubsan] Fix some UBSAN warnings

Passing nullptr to memset/memcpy is UB, even if the size passed in is 0.
Avoid making such calls when we don't yet have a buffer to write into.

Avoid possible signed integer overflow.

This is basically a cherry-pick of
https://github.com/protocolbuffers/protobuf/commit/d14cacd791ac553b5dfba5f303fc631b42f6e662
and
https://github.com/protocolbuffers/protobuf/commit/0f8e6d1402fc021e02b9def83df9a9683ba6ea76

Change-Id: I286e90dd247c25cf4757cbf4bc92ab578b5d7bdb
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/protobuf/+/426575
Reviewed-by: Roland McGrath <mcgrathr@google.com>
3 files changed
tree: 75aa7d408308e74aa6a6338af95ee2c7adf57f13
  1. benchmarks/
  2. cmake/
  3. conformance/
  4. csharp/
  5. docs/
  6. editors/
  7. examples/
  8. java/
  9. javanano/
  10. jenkins/
  11. js/
  12. kokoro/
  13. m4/
  14. more_tests/
  15. objectivec/
  16. php/
  17. protoc-artifacts/
  18. python/
  19. ruby/
  20. src/
  21. test/
  22. third_party/
  23. util/
  24. .gitignore
  25. .gitmodules
  26. .travis.yml
  27. appveyor.bat
  28. appveyor.yml
  29. autogen.sh
  30. BUILD
  31. BUILD.gn
  32. CHANGES.txt
  33. composer.json
  34. configure.ac
  35. CONTRIBUTORS.txt
  36. generate_changelog.py
  37. generate_descriptor_proto.sh
  38. gmock.BUILD
  39. LICENSE
  40. Makefile.am
  41. post_process_dist.sh
  42. proto_library.gni
  43. protobuf-lite.pc.in
  44. protobuf.bzl
  45. protobuf.pc.in
  46. Protobuf.podspec
  47. protoc_wrapper.py
  48. README.fuchsia
  49. README.md
  50. six.BUILD
  51. tests.sh
  52. update_file_lists.sh
  53. WORKSPACE
README.md

Protocol Buffers - Google's data interchange format

Build Status Build status Build Status Build Status Build Status

Copyright 2008 Google Inc.

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

Overview

Protocol Buffers (a.k.a., protobuf) are Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data. You can find protobuf's documentation on the Google Developers site.

This README file contains protobuf installation instructions. To install protobuf, you need to install the protocol compiler (used to compile .proto files) and the protobuf runtime for your chosen programming language.

Protocol Compiler Installation

The protocol compiler is written in C++. If you are using C++, please follow the C++ Installation Instructions to install protoc along with the C++ runtime.

For non-C++ users, the simplest way to install the protocol compiler is to download a pre-built binary from our release page:

https://github.com/google/protobuf/releases

In the downloads section of each release, you can find pre-built binaries in zip packages: protoc-$VERSION-$PLATFORM.zip. It contains the protoc binary as well as a set of standard .proto files distributed along with protobuf.

If you are looking for an old version that is not available in the release page, check out the maven repo here:

https://repo1.maven.org/maven2/com/google/protobuf/protoc/

These pre-built binaries are only provided for released versions. If you want to use the github master version at HEAD, or you need to modify protobuf code, or you are using C++, it's recommended to build your own protoc binary from source.

If you would like to build protoc binary from source, see the C++ Installation Instructions.

Protobuf Runtime Installation

Protobuf supports several different programming languages. For each programming language, you can find instructions in the corresponding source directory about how to install protobuf runtime for that specific language:

LanguageSource
C++ (include C++ runtime and protoc)src
Javajava
Pythonpython
Objective-Cobjectivec
C#csharp
JavaNanojavanano
JavaScriptjs
Rubyruby
Gogolang/protobuf
PHPphp
Dartdart-lang/protobuf

Quick Start

The best way to learn how to use protobuf is to follow the tutorials in our developer guide:

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

If you want to learn from code examples, take a look at the examples in the examples directory.

Documentation

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

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