lz4

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LZ4 CODING STYLE
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================
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When contributing code and patches to the `LZ4` project, the following rules are expected to be followed for a successful merge.
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Library
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-------
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The library's source code in `lib/` directory has a BSD 2-clause license.
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It's designed to be integrated into 3rd party applications.
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It adheres relatively strictly to vanilla `C90`, with the following exceptions:
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- `long long` type is required, in order to support 64-bit values
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- Variadic Macros are used for debug mode (but not required in release mode)
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Beyond that, all other rules and limitations of C90 must be respected, including `/* ... */` comment style only, and variable declaration at top of block only. The automated CI test suite will check for these rules.
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The code is allowed to use more modern variants (C99 / C11 / C23) when useful
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as long as it provides a clean C90 backup for older compilers.
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For example, C99+ compilers will employ the `restrict` keyword, while `C90` ones will ignore it, thanks to conditional macros.
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This ensures maximum portability across a wide range of systems.
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Moreover, in the interest of safety, the code has to respect a fairly strigent list of additional restrictions, provided through warning flags, the list of which is maintained within `Makefile`.
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Among the less common ones, we want the source to be compatible with `-Wc++-compat`, which ensures that the code can be compiled "as is", with no modification, as C++ code. It makes it possible to copy-paste the code into other C++ source files, or the source files are just dropped into a C++ environment which then compiles them as C++ source files.
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Command Line Interface
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The CLI executable's source code in `programs/` directory has a GPLv2+ license.
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While it's designed to be portable and freely distributable, it's not meant to be integrated into 3rd party applications.
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The license difference is meant to reflect that choice.
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Similar to the library, the CLI adheres relatively strictly to vanilla `C90`, and features the same exceptions:
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- `long long` requirement for 64-bit values
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- Variadic Macros for console messages (now used all the time, not just debug mode)
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The code can also use system-specific libraries and symbols (such as `posix` ones)
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as long as it provides a backup for plain `C90` platforms.
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It's even allowed to lose capabilities, as long as the CLI can be cleanly compiled on `C90`.
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For example, systems without `<pthread>` support nor Completion Ports will just not feature multi-threading support, and run single threaded.
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In the interest of build familiarity, the CLI source code also respects the same set of advanced warning flags as the library.
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That being said, this last part is debatable and could deviate in the future.
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For example, there are less reasons to support `-Wc++-compat` on the CLI side, since it's not meant to be integrated into 3rd party applications.
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Others
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The repository includes other directories with their own set of compilable projects, such as `tests/`, `examples/` and `contrib/`.
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These repositories do not have to respect the same set of restrictions, and can employ a larger array of different languages.
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For example, some tests employ `sh`, and others employ `python`.
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These directories may nonetheless include several targets employing the same coding convention as the `lz4` library. This is in a no way a rule, more like a side effect of build familiarity.
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