doc/ref/libguile-parallel.texi

   1 @c -*-texinfo-*-
   2 @c This is part of the GNU Guile Reference Manual.
   3 @c Copyright (C)  1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, 2011, 2013
   4 @c   Free Software Foundation, Inc.
   5 @c See the file guile.texi for copying conditions.
   6
   7 @node Parallel Installations
   8 @section Parallel Installations
   9
  10 @cindex pkg-config
  11 @cindex effective version
  12
  13 Guile provides strong API and ABI stability guarantees during stable
  14 series, so that if a user writes a program against Guile version 2.2.3,
  15 it will be compatible with some future version 2.2.7.  We say in this
  16 case that 2.2 is the @dfn{effective version}, composed of the major and
  17 minor versions, in this case 2 and 2.
  18
  19 Users may install multiple effective versions of Guile, with each
  20 version's headers, libraries, and Scheme files under their own
  21 directories.  This provides the necessary stability guarantee for users,
  22 while also allowing Guile developers to evolve the language and its
  23 implementation.
  24
  25 However, parallel installability does have a down-side, in that users
  26 need to know which version of Guile to ask for, when they build against
  27 Guile.  Guile solves this problem by installing a file to be read by the
  28 @code{pkg-config} utility, a tool to query installed packages by name.
  29 Guile encodes the version into its pkg-config name, so that users can
  30 ask for @code{guile-2.0} or @code{guile-2.2}, as appropriate.
  31
  32 For effective version @value{EFFECTIVE-VERSION}, for example, you would
  33 invoke @code{pkg-config --cflags --libs guile-@value{EFFECTIVE-VERSION}}
  34 to get the compilation and linking flags necessary to link to version
  35 @value{EFFECTIVE-VERSION} of Guile.  You would typically run
  36 @code{pkg-config} during the configuration phase of your program and use
  37 the obtained information in the Makefile.
  38
  39 Guile's @code{pkg-config} file,
  40 @file{guile-@value{EFFECTIVE-VERSION}.pc}, defines additional useful
  41 variables:
  42
  43 @table @code
  44 @item sitedir
  45 @cindex @code{sitedir}
  46 The default directory where Guile looks for Scheme source and compiled
  47 files (@pxref{Installing Site Packages, %site-dir}).  Run
  48 @command{pkg-config guile-@value{EFFECTIVE-VERSION} --variable=sitedir}
  49 to see its value.  @xref{Autoconf Macros, GUILE_SITE_DIR}, for more on
  50 how to use it from Autoconf.
  51
  52 @item extensiondir
  53 @cindex @code{extensiondir}
  54 The default directory where Guile looks for extensions---i.e., shared
  55 libraries providing additional features (@pxref{Modules and
  56 Extensions}).  Run @command{pkg-config guile-@value{EFFECTIVE-VERSION}
  57 --variable=extensiondir} to see its value.
  58 @end table
  59
  60 @noindent
  61 See the @code{pkg-config} man page, for more information, or its web
  62 site, @url{http://pkg-config.freedesktop.org/}.
  63 @xref{Autoconf Support}, for more on checking for Guile from within a
  64 @code{configure.ac} file.
  65
  66
  67 @c Local Variables:
  68 @c TeX-master: "guile.texi"
  69 @c End: