library-combo(7)					       GNUstep System Manual						  library-combo(7)

NAME

       library-combo - GNUstep Make support for cross-compilation.

DESCRIPTION

       This  manual  page  is  about  cross-compilation and fat binaries. Fat binaries are packages that you can supply which contain more the one
       binary of your program (e.g. your application). So you can support multiple platforms with a single package.

       To support this your system has to be built in a non-flattened way. Meaning that during the installation of gnustep-make  you  should  have
       selected  --disable-flattened  and  the	types  of  library combinations you want to support, through the --with-library-combo option. With
       library combinations we mean the Objective-C runtime, the Foundation library and the Application library. For more details about  this  see
       the LIBRARY-COMBO section.

       If  you	installed  your  GNUstep  system  in  a  non-flattened	way  all  system  dependend  binaries are installed in subdirectories with
       cpu/os/library-combo   information.   That   means   for   instance   that   the   gnustep-base	  library    will    be    installed	in
       Library/Libraries/ix86/linux/gnu-gnu-gnu/  when	you are on an Intel x86 system, running linux with the GNU runtime for Objective-C and you
       installed GNUstep.

       For each and every library-combo that you want to support you should create the environment through gnustep-make,  because  it  installs  a
       different config.make to support its own CC, OPTFLAGS, etc. flags.

   LIBRARY-COMBO
       An important issue is to let to a package the ability to deal with various libraries and configurations available now:

       Objective-C runtimes
	      In  the  Objective-C  world  there  are three major runtimes: the NeXT runtime, the Apple runtime and the GNU runtime (both with and
	      without garbage collection enabled). They are different in several respects and a program or library that works at the runtime level
	      should be aware of them.

       Foundation libraries
	      There  are  several  Foundation  libraries  an  application  or tool can be written on top of: NeXT Foundation library which runs on
	      NeXTStep/OPENSTEP systems, gnustep-base, libFoundation and Apple Cocoa system.

       Graphical interfaces
	      Until now three libraries provide or try to provide OpenStep compliant systems: the AppKit from NeXT,  gnustep-gui  and  Cocoa  from
	      Apple.

       If  a program wants to work with all the possible combinations it will have to provide different binaries for each combination because it's
       not possible to have a tool compiled for NeXT Foundation that runs with gnustep-base or vice-versa. To summarize, a program can be compiled
       for these combinations:

       Objective-C runtime
	      nx (for NeXT), gnu (for GNU without garbage collection), gnugc (for GNU with garbage collection), apple (for Apple)

       Foundation library
	      nx (for NeXT), gnu (for gnustep-base), fd (for libFoundation), apple (for Apple Cocoa)

       GUI library
	      nx (for NeXT), gnu (for gnustep-gui), apple (for Apple Cocoa)

       We'll denote the fact that an application was compiled for a certain combination of the above values by using the abbreviations of the dif-
       ferent subsystems and placing dashes between them. For example an application compiled for NeXT Foundation using NeXT AppKit will have  the
       compile	attribute  nx-nx-nx. An application compiled for Apple Cocoa with the GNU compiler for Objective-C gnu-apple-apple and another one
       compiled for gnustep-base using gnustep-gui under Unix will be denoted by gnu-gnu-gnu. Here is a list of some of the possible combinations:

	  Runtime     Foundation     GUI
	    nx		  nx	     nx
	    nx		  fd	     gnu
	    gnu 	  gnu	     gnu
	    gnu 	  fd	     gnu
	   gnugc	  gnu	     gnu
	   gnugc	  fd	     gnu
	   apple	 apple	     apple
	   apple	  gnu	     gnu

       Note that one can choose his/her own packages to build; it is not required to have all the packages installed on the system. Not having all
       of them installed limits only the ability to build and distribute binaries for those missing combinations.

   DIRECTORY STRUCTURE
       For cross-compilation in a non-flattened directory structure is recommended, so that you can store on the same directory structure binaries
       for different machines.	The standard GNUstep filesystem layout is normally used when a non-flattened directory structure  is  being  used;
       this  is  obtained  with  the  --with-layout=gnustep option when configuring gnustep-make.  The entire GNUstep installation is then created
       inside /usr/GNUstep (or another directory if you use the --prefix=...  option when configuring  gnustep-make).	Directories  that  contain
       binaries (such as the Libraries directory) inside /usr/GNUstep are then set up to support fat binaries as follows:

       Libraries/
	 ix86/
	   linux-gnu/
	     gnu-gnu-gnu/
		 libgnustep-base.so
		 libgnustep-gui.so
	     gnu-fd-gnu/
		 libFoundation.so
		 libgnustep-gui.so

       To  allow the right libraries to be found, you need to source GNUstep.sh before using GNUstep, and you need to start up your application by
       using openapp, which will locate the right binary for your library combo.

   BUILDING FOR A LIBRARY-COMBO
       The makefile package will allow the user to choose between different library combinations. To specify a combination you want to compile for
       just type:

	 $ make library_combo=library-combo

       For  instance if you want to choose to compile using the GNUstep's Foundation implementation and use the GNUstep GUI library on a GNU/Linux
       machine you can do like this:

	 $ make library_combo=gnu-gnu-gnu

       If your project requires running configure before compiling there are two issues you have to keep in mind. 'configure' is used to determine
       the  existence  of  particular header files and/or of some specific functionality in the system header files. This thing is usually done by
       creating a config.h file which contains a couple of defines like HAVE_... which say if the checked functionality is present or not.

       Another usage of configure is to determine some specific libraries to link against to and/or some specific tools. A typical GNUstep program
       is  not	required to check for additional libraries because this step is done by the time the makefile package is installed. If the project
       still needs to check for additional libraries and/or tools, the recommended way is to output a config.mak file which  is  included  by  the
       main GNUmakefile, instead of using Makefile.in files which are modified by configure.  The reason for not doing this is to avoid having the
       makefiles contain target dependencies like above, this way keeping only one makefile instead of several for each target machine.

       The makefile package is written for GNU make because it provides some very powerful features that save time both in writing the package but
       also at runtime, when you compile a project.

   BUILDING FOR AN ARCHITECTURE
       In  order  to  build  a project for multiple architectures you'll need the development environment for the target machine installed on your
       machine. This includes a cross-compiler together with all the additional tools like the assembler and linker, the target header	files  and
       all the libraries you need.

       The GNUstep makefile package should be able to compile and link an application for another machine just by typing

	 $ make target=target-triplet

       where target-triplet is the canonical system name as reported by config.guess.

   USING A LIBRARY-COMBO
       When  you use library-combos, you must always source GNUstep.sh.  That allows you to switch library paths on the fly. If you want to switch
       to a different library-combo in your shell, and if you are using bash, it's common to first source  GNUstep-reset.sh  to  reset	all  shell
       variables,  then  to  source  GNUstep.sh  again.  Let's	assume	we  use  gnu-gnu-gnu as our current LIBRARY_COMBO and we want to switch to
       gnugc-gnu-gnu, then we would use:

	 . /usr/GNUstep/System/Library/Makefiles/GNUstep-reset.sh
	 export LIBRARY_COMBO=gnugc-gnu-gnu
	 . /usr/GNUstep/System/Library/Makefiles/GNUstep.sh

SEE ALSO

       debugapp(1), GNUstep(7), gnustep-config(1), openapp(1)

HISTORY

       Work on gnustep-make started in 1997 by Scott Christley <scottc@net-community.com>.

       Version 2.0.0 of gnustep-make introduced many changes with previous releases, which was mainly the work of Nicola  Pero	<nicola.pero@meta-
       innovation.com>

AUTHORS

       This man-page was written by Dennis Leeuw <dleeuw@made-it.com> based on the DESIGN document from the gnustep-make source tree.

CREDITS

       The DESIGN document was written by Ovidiu Predescu.

       This work could only be as is due to the notes and corrects from Nicola Pero <nicola.pero@meta-innovation.com>.

COPYRIGHT

       Copyright (C) 2007 Free Software Foundation, Inc.

       Copying	and  distribution  of  this file, with or without modification, are permitted in any medium without royalty provided the copyright
       notice and this notice are preserved.

gnustep-make							    20/12/2007							  library-combo(7)