Code Style Guide

All of the C++ code in the project is styled. You should run any changes you make through astyle before pushing a pull request.

We are using astyle version 3.1. Other versions of astyle produce different formatting and should not be used.

Blocks of code can be passed through astyle to ensure that their formatting is correct:

astyle --style=1tbs --attach-inlines --indent=spaces=4 --align-pointer=name --max-code-length=100 --break-after-logical --indent-classes --indent-preprocessor --indent-switches --indent-col1-comments --min-conditional-indent=0 --pad-oper --unpad-paren --pad-paren-in --add-brackets --convert-tabs --exclude=src/third-party --ignore-exclude-errors-x

These options are mirrored in .astylerc, Cataclysm-DDA.sublime-project and doc/CODE_STYLE.txt

For example, from vi, set marks a and b around the block, then:

:'a,'b ! astyle  --style=1tbs --attach-inlines --indent=spaces=4 --align-pointer=name --max-code-length=100 --break-after-logical --indent-classes --indent-preprocessor --indent-switches --indent-col1-comments --min-conditional-indent=0 --pad-oper --unpad-paren --pad-paren-in --add-brackets --convert-tabs --exclude=src/third-party --ignore-exclude-errors-x

See DEVELOPER_TOOLING.md for other environments.

Code Example

Here’s an example that illustrates the most common points of style:

int foo( int arg1, int *arg2 )
{
    if( arg1 < 5 ) {
        switch( *arg2 ) {
            case 0:
                return arg1 + 5;
                break;
            case 1:
                return arg1 + 7;
                break;
            default:
                return 0;
                break;
        }
    } else if( arg1 > 17 ) {
        int i = 0;
        while( i < arg1 ) {
            printf( _( "Really long message that's pointless except for the number %d and for its "
                       "length as it's illustrative of how to break strings properly.\n" ), i );
        }
    }
    return 0;
}

Code Guidelines

These are less generic guidelines and more pain points we’ve stumbled across over time.

  1. Use int for everything.
    1. long in particular is problematic since it is not a larger type than int on platforms we care about.
      1. If you need an integral value larger than 32 bits, you don’t. But if you do, use int64_t.
    2. Uint is also a problem: it has poor behavior when overflowing and should be avoided for general purpose programming.
      1. If you need binary data, unsigned int or unsigned char are fine, but you should probably use std::bitset instead.
    3. float is to be avoided, but it has valid uses.
  2. Almost Always Avoid Auto. Auto has two uses; others should be avoided.
    1. Aliasing for extremely long iterator or functional declarations.
    2. Generic code support (but decltype is better).
  3. Avoid using declaration for standard namespaces.
  4. Keep lambda small or avoid them. There should be no substantial logic in lambdas.
    1. If you need code reuse, hoist the code to a helper function or method.
    2. Avoid implicit capture ( [&] or [=] ).