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
GNUstep runtime, the Apple runtime and the GNU runtime. 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 different Foundation libraries an application or tool
can be written on top of: 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
ng (for GNUstep Next Generation), gnu (for GNU , or for GNUstep
without latest language features), apple (for Apple), nx (for
NeXT)
Foundation library
gnu (for gnustep-base), fd (for libFoundation), apple (for Apple
Cocoa), nx (for NeXT Foundation)
GUI library
gnu (for gnustep-gui), apple (for Apple Cocoa), nx (for NeXT
GUI)
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
ng 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.
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