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Gnubs pres-foss-cdac-sem
1. Presentation
on
GNU Build System
for
(FOSS) From the Open Source Shelf
CDAC Monthly Seminar Series
Presented by
Sagun Baijal
Organised by
CDAC, Kharghar, Navi Mumbai
E-mail: course_kh@cdacmumbai.in
4. Background
• Typical Methods of installing a software in Unix-
like systems
• Installation by using a package manager
• Installtion from source code
• GNU standard method of installation
• Packages normally come as a tarball.
• Decompress the package.
• Run configure script e.g. ...:~$./configure
• Run make e.g. ...:~$make
• Run make install e.g. ...:~$sudo make install
5. Background contd...
• Issues while packaging the system for release
• Naming and Versioning of the package.
• Portability of system on a variety of platforms.
• Configuration script configure with standrad
configurations options.
• Makefile.inS required by configure script.
• Conformity of Makefile and directory layout as per
GNU standards.
• Necessary documentation files and tests.
• Bundling of the package into a tarball.
• Licensing of the system.
6. Why GNU Build System
• Creating a configuration script and Makefiles
from scratch is a tedious, time-consuming and
error-prone task.
• Some users may be left unsatisfied due to
unavailability of some desired features.
• It may be needed to upgrade the overall setup to
follow the changes to the GNU Coding Standards.
7. Contd...
• GNU Build System helps:
• simplify the development of portable programs.
• simplify the building of programs distributed as
source code.
• Any bux fixes and improvements can be made at
one place.
• Users don't require any utilities of build system
at their end.
8. Introduction to GNU Build System
• GNU Build System comprises:
• autoconf: For generating configuration script configure.
• automake: For generating makefile templates
Makfile.inS
• libtool: Helps creating the portable compiled libraries.
• Some other auxilary tools:
• Autoscan: For generating intial input file for autoconf.
• Autoheader: For generating template header for
configure.
• aclocal: For generating aclocal.m4.
9. Contd...
• Installation:
• To check, if installed in their most recent versions:
• ...:~$autoconf - -version
• ...:~$automake - -version
• ...:~$libtool - -version
• If not installed, then (on any debian-like system):
• ...:~$apt-cache search <tool-name> - searches for the
tool-name in available package list.
• ...:~$sudo apt-get install <tool-name> - installs the
<tool-name>.
10. Using GNU Build System
• Basic requirements:
Source and documentation files of the package.
•
• One configure.ac/.in as initial input file for
autoconf.
• One Makefile.am for each directory in the package.
• Source and Documentation files:
• Files containing source code and necessary
documentation to be distributed in the package.
• Ex.: .c, .cpp files, README etc..
11. Contd...
• What is configure.ac?
• Initial input file for autoconf to generate configure
script. Also used by automake, while creating
Makefile.amS.
• Contains macros needed to test the system features
required or used by the package.
• Using autoscan:
• autoscan scans source files and creates configure.scan.
• After making some adjustments, if required,
configure.scan can be renamed to configure.ac.
• Adjustments may be like adding some missing macros
or changing the order of some macros etc..
12. Contd...
• Common macros:
• AC_PREREQ: specifies the minimum version of autoconf that can
successfully compile a given configure.ac.
• AC_INIT: initializes autoconf.
• AM_INIT_AUTOMAKE: initializes automake.
• AC_PROG_CC: determines a C compiler to use and sets output
variable CC to its value.
• AC_PROG_CXX: determines a C++ compiler to use and sets output
variable CXX to its value.
• AC_CONFIG_HEADER: causes to create a config.h file gathering
‘#define’s defined by other macros in configure.ac.
• AC_CONFIG_FILES: declares the list of files to be created from their
*.in templates.
• AC_OUTPUT: generates and runs config.status, which in turn creates
the makefiles and any other files resulting from configuration.
14. Contd...
• What is Makefile.am?
• Initial input file for automake to generate
Makefile.in.
• One Makefile.am for each directory in package
including root directory.
• Normally contains a list of variable (and rule)
definitions required when make is invoked.
• Common Makefile targets:
• make all: Build programs, libraries, documentation,
etc.
• make install: Install what needs to be installed,
copying the files from the package's tree to system-
wide directories.
15. Contd...
• make uninstall: The opposite of make install: erase the
installed files.
• make clean: Erase from the build tree the files built by
make all.
• make distclean: Additionally erase anything
./configure created.
• make check: Run the test suite, if any.
• make installcheck: Check the installed programs or
libraries, if supported.
• make dist: Recreate package-version.tar.gz from all
the source files.
16. Contd...
• Common variables for Makefile.am:
• bin_PROGRAMS: specifies the <program> to be built
and installed on .../bin directory.
• <program>_SOURCES: lists one or more source files
compiled to build the <program>.
• SUBDIRS: lists all sub-directories to be built.
• dist_doc_DATA: lists documentation files to be
distributed and installed in ../doc directory.
• <program>_DEPENDENCIES: specifies dependencies,
if any.
• <program>_<FLAGS>: various compilation flags can
be set.
17. Contd...
• <program>_LDADD: specifies extra objects and
libraries to be added with <program>.
• <program>_LDFLAGS: specifies extra linker flags for
<program>.
• An example Makefile.am:
bin_PROGRAMS = hello
hello_SOURCES = hello.c
18. Contd...
• Some characteristics of GNU Build System:
• VPATH Builds: When source tree and build tree
are different, such builds are called VPATH builds.
• Cross-compilation: When a program is built on one
platform and run on another platform is called
cross-compilation.
• Renaming: GNU build system allows to
automatically rename executables etc. before
installation.
• Dependency tracking: GNU build system allows to
track dependencies automatically.
• Nested packages: Autoconfiscated packages can be
nested to arbitrary depth.
19. Contd...
• Applying tools to create the package:
• Ensure all necessary source, documentation and
Makefiel.amS files have been created.
• Run autoscan to create prelimanary configure.scan.
• ..:~/<pkg-dir>$autoscan
• If required, edit configure.scan to update package-
name, version, invocation to
AM_INIT_AUTOMAKE macro etc. and rename it
to configure.ac.
• Run aclocal to create aclocal.m4. This file contains
macro definitions not part of standard autoconf
macros.
• ..:~/<pkg-dir>$aclocal
20. Contd...
• Run autoheader to create config.h.in. This file is a
template header for configure.
• ..:~/<pkg-dir>$autoheader
• Run autoconf to create configure from configure.ac
and aclocal.m4.
• ..:~/<pkg-dir>$autoconf
• Run automake to create Makefile.inS from
Makefile.amS.
• ..:~/<pkg-dir>$automake
• Run configure to create Makefiles from
Makefile.inS, config.h from config.h.in and perform
various checks about the environment.
• ..:~/<pkg-dir>$./configure
21. Contd...
• Now run make to build the system.
• ..:~/<pkg-dir>$make
• If make executes successfully, run make distcheck to
create the package for distribution as a tarball.
• ..:~/<pkg-dir>$make distcheck
• Run make install to install the package.
• ..:~/<pkg-dir>$sudo make install
• Run make uninstall to uninstall the package.
• ..:~/<pkg-dir>$sudo make uninstall
22. Conclusion
• From User's point of view:
• provides a standard procedure for installation.
• procedure consists of only a small set of commands.
• From Developer's point of view:
• Creating portable distributions become easy.
• Updations or improvements, if any, can be done at
one place.
