Re: package dependencies

[ludo@gnu.org (Ludovic Courtès)]

Hello!

I’ve rephrased the doc in “package Reference” in a way that is hopefully
clearer:

     ‘inputs’ (default: ‘'()’)
     ‘native-inputs’ (default: ‘'()’)
     ‘propagated-inputs’ (default: ‘'()’)
          These fields list dependencies of the package.  Each one is a
          list of tuples, where each tuple has a label for the input (a
          string) as its first element, a package, origin, or derivation
          as its second element, and optionally the name of the output
          thereof that should be used, which defaults to ‘"out"’ (*note
          Packages with Multiple Outputs::, for more on package
          outputs).  For example, the list below specifies 3 inputs:

               `(("libffi" ,libffi)
                 ("libunistring" ,libunistring)
                 ("glib:bin" ,glib "bin"))  ;the "bin" output of Glib

          The distinction between ‘native-inputs’ and ‘inputs’ is
          necessary when considering cross-compilation.  When
          cross-compiling, dependencies listed in ‘inputs’ are built for
          the _target_ architecture; conversely, dependencies listed in
          ‘native-inputs’ are built for the architecture of the _build_
          machine.

          ‘native-inputs’ is typically where you would list tools needed
          at build time but not at run time, such as Autoconf, Automake,
          pkg-config, Gettext, or Bison.  ‘guix lint’ can report likely
          mistakes in this area (*note Invoking guix lint::).

          Lastly, ‘propagated-inputs’ is similar to ‘inputs’, but the
          specified packages will be force-installed alongside the
          package they belong to (*note ‘guix package’:
          package-cmd-propagated-inputs, for information on how ‘guix
          package’ deals with propagated inputs.)

          For example this is necessary when a library needs headers of
          another library to compile, or needs another shared library to
          be linked alongside itself when a program wants to link to it.

HTH!

Ludo’.