1.9 Breaking long lines

With the option ‘-ln’, or ‘--line-lengthn’, it is possible to specify the maximum length of a line of C code, not including possible comments that follow it.

When lines become longer than the specified line length, GNU indent tries to break the line at a logical place. This is new as of version 2.1 however and not very intelligent or flexible yet.

Currently there are two options that allow one to interfere with the algorithm that determines where to break a line.

The ‘-bbo’ option causes GNU indent to prefer to break long lines before the boolean operators && and ||. The ‘-nbbo’ option causes GNU indent not have that preference. For example, the default option ‘-bbo’ (together with ‘--line-length60’ and ‘--ignore-newlines’) makes code look like this:

  if (mask
      && ((mask[0] == '\0')
          || (mask[1] == '\0'
              && ((mask[0] == '0') || (mask[0] == '*')))))

Using the option ‘-nbbo’ will make it look like this:

  if (mask &&
      ((mask[0] == '\0') ||
       (mask[1] == '\0' &&
        ((mask[0] == '0') || (mask[0] == '*')))))

The default ‘-hnl’, however, honours newlines in the input file by giving them the highest possible priority to break lines at. For example, when the input file looks like this:

  if (mask
      && ((mask[0] == '\0')
      || (mask[1] == '\0' && ((mask[0] == '0') || (mask[0] == '*')))))

then using the option ‘-hnl’, or ‘--honour-newlines’, together with the previously mentioned ‘-nbbo’ and ‘--line-length60’, will cause the output not to be what is given in the last example but instead will prefer to break at the positions where the code was broken in the input file:

  if (mask
      && ((mask[0] == '\0')
          || (mask[1] == '\0' &&
              ((mask[0] == '0') || (mask[0] == '*')))))

The idea behind this option is that lines which are too long, but are already broken up, will not be touched by GNU indent. Really messy code should be run through indent at least once using the ‘--ignore-newlines’ option though.

This document was generated by david on December, 15 2008 using texi2html 1.78.