Provided by: gnustep-common_2.6.6-3_amd64 
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 different 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.