Wladimir J. van der Laan e5d47ed8fd
Merge #18167: Fix a violation of C++ standard rules where unions are used for type-punning
0653939ac130eddffe40c53ac418bea305d3bf82 Add static_asserts to ser_X_to_Y() methods (Samer Afach)
be94096dfb0c4862e2314cbae4120d7360b08ef2 Fix a violation of C++ standard rules that unions cannot be switched. (Samer Afach)

Pull request description:

  Type punning in C++ is not like C. As per the C++ standard, one cannot use unions to convert the bit type. A discussion about this can be found [here](https://stackoverflow.com/questions/25664848/unions-and-type-punning). In C++, a union is supposed to only hold one type at a time. It's intended to be used only as `std::variant`. Switching types is undefined behavior.

  In fact, C++20 has a special casting function, called [`bit_cast`](https://en.cppreference.com/w/cpp/numeric/bit_cast) that solved this problem.

  Why has it been working so far? Because some compilers tolerate using unions and switching types, like gcc. More information [here](https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Type-punning).

  One important thing to mention is that performance is generally not affected by that memcpy. Compilers are smart enough to convert that to a memory cast when possible. But we have to do it the right way, otherwise, it's jut undefined behavior that depends on the compiler.

ACKs for top commit:
  practicalswift:
    ACK 0653939ac130eddffe40c53ac418bea305d3bf82
  elichai:
    ACK 0653939ac130eddffe40c53ac418bea305d3bf82
  laanwj:
    Code review ACK 0653939ac130eddffe40c53ac418bea305d3bf82
  kristapsk:
    ACK 0653939ac130eddffe40c53ac418bea305d3bf82

Tree-SHA512: f6e89de39fc964750429139bab6b5a1346f7060334b7afa020e315bdad8f8c195bce2b8a9e343f06e7fff175e2dfb1cdabfcb6fe405bea0febe4962f0cc62557
2020-02-26 19:00:24 +01:00
2019-09-02 13:40:01 +02:00
2019-11-18 08:56:48 -05:00
2019-12-26 23:11:21 +01:00
2019-11-04 04:22:53 -05:00

Bitcoin Core integration/staging tree

https://bitcoincore.org

What is Bitcoin?

Bitcoin is an experimental digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: managing transactions and issuing money are carried out collectively by the network. Bitcoin Core is the name of open source software which enables the use of this currency.

For more information, as well as an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/, or read the original whitepaper.

License

Bitcoin Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/licenses/MIT.

Development Process

The master branch is regularly built and tested, but is not guaranteed to be completely stable. Tags are created regularly to indicate new official, stable release versions of Bitcoin Core.

The contribution workflow is described in CONTRIBUTING.md and useful hints for developers can be found in doc/developer-notes.md.

Testing

Testing and code review is the bottleneck for development; we get more pull requests than we can review and test on short notice. Please be patient and help out by testing other people's pull requests, and remember this is a security-critical project where any mistake might cost people lots of money.

Automated Testing

Developers are strongly encouraged to write unit tests for new code, and to submit new unit tests for old code. Unit tests can be compiled and run (assuming they weren't disabled in configure) with: make check. Further details on running and extending unit tests can be found in /src/test/README.md.

There are also regression and integration tests, written in Python, that are run automatically on the build server. These tests can be run (if the test dependencies are installed) with: test/functional/test_runner.py

The Travis CI system makes sure that every pull request is built for Windows, Linux, and macOS, and that unit/sanity tests are run automatically.

Manual Quality Assurance (QA) Testing

Changes should be tested by somebody other than the developer who wrote the code. This is especially important for large or high-risk changes. It is useful to add a test plan to the pull request description if testing the changes is not straightforward.

Translations

Changes to translations as well as new translations can be submitted to Bitcoin Core's Transifex page.

Translations are periodically pulled from Transifex and merged into the git repository. See the translation process for details on how this works.

Important: We do not accept translation changes as GitHub pull requests because the next pull from Transifex would automatically overwrite them again.

Translators should also subscribe to the mailing list.

Description
No description provided
Readme 223 MiB
Languages
C++ 61.6%
Python 15.9%
C 11.9%
Assembly 6.2%
M4 1.6%
Other 2.7%