-@node Library vs. Reusable Code
+@node Benefits
+@section Benefits of using Gnulib
+
+Gnulib is useful to enhance various aspects of a package:
+
+@itemize @bullet
+@item
+Portability: With Gnulib, a package maintainer can program against the
+POSIX and GNU libc APIs and nevertheless expect good portability to
+platforms that don't implement POSIX.
+
+@item
+Maintainability: When a package uses modules from Gnulib instead of code
+written specifically for that package, the maintainer has less code to
+maintain.
+
+@item
+Security: Gnulib provides functions that are immune against vulnerabilities
+that plague the uses of the corresponding commonplace functions. For
+example, @code{asprintf}, @code{canonicalize_file_name} are not affected
+by buffer sizing problems that affect @code{sprintf}, @code{realpath}.
+@code{openat} does not have the race conditions that @code{open} has. Etc.
+
+@item
+Reliability: Gnulib provides functions that combine a call to a system
+function with a check of the result. Examples are @code{xalloc},
+@code{xprintf}, @code{xstrtod}, @code{xgetcwd}.
+
+@item
+Structure: Gnulib offers a way to structure code into modules, typically
+one include file, one source code file, and one autoconf macro for each
+functionality. Modularity helps maintainability.
+@end itemize
+
+@node Library vs Reusable Code
@section Library vs. Reusable Code
Classical libraries are installed as binary object code. Gnulib is
Similarly, Gnulib has a facility for executing a command in a
subprocess. It is at the same time a portability enhancement (it
works on GNU, Unix, and Windows, compared to the classical
-@code{fork()}/@code{exec()} which is not portable to Windows), as well
+@code{fork}/@code{exec} idiom which is not portable to Windows), as well
as an application aid: it takes care of redirecting stdin and/or
stdout if desired, and emits an error message if the subprocess
failed.
+@node Target Platforms
+@section Target Platforms
+
+Gnulib supports a number of platforms that we call the ``reasonable
+portability targets''. This class consists of widespread operating systems,
+for three years after their last availability, or --- for proprietary
+operating systems --- as long as the vendor provides commercial support for
+it. Already existing Gnulib code for older operating systems is usually
+left in place for longer than these three years. So it comes that programs
+that use Gnulib run pretty well also on these older operating systems.
+
+Some operating systems are not very widespread, but are Free Software and
+are actively developed. Such platforms are also supported by Gnulib, if
+that OS's developers community keeps in touch with the Gnulib developers,
+by providing bug reports, analyses, or patches. For such platforms, Gnulib
+supports only the versions of the last year or the last few months,
+depending on the maturity of said OS project, the number of its users, and
+how often these users upgrade.
+
+Niche operating systems are generally unsupported by Gnulib, unless some
+of their developers or users contribute support to Gnulib.
+
+The degree of support Gnulib guarantees for a platform depends on the
+amount of testing it gets from volunteers. Platforms on which Gnulib
+is frequently tested are the best supported. Then come platforms with
+occasional testing, then platforms which are rarely tested. Usually,
+we fix bugs when they are reported. Except that some rarely tested
+platforms are also low priority; bug fixes for these platforms can
+take longer.
+
+As of 2011, the list of supported platforms is the following:
+
+@itemize
+@item
+glibc systems. With glibc 2.8 or newer, they are frequently tested. With
+glibc 2.3 or newer, they are occasionally tested.
+@item
+MacOS X. In versions 10.5 and 10.6, it's frequently tested. In version
+10.4, it's rarely tested.
+@item
+FreeBSD 6.0 or newer is occasionally tested. FreeBSD 5.x is rarely tested.
+@item
+NetBSD 5.0 or newer is occasionally tested. NetBSD 3.0 or newer is rarely
+tested.
+@item
+OpenBSD 4.0 or newer is occasionally tested. OpenBSD 3.8 or newer is rarely
+tested.
+@item
+AIX 6.1 or newer is occasionally tested. AIX 5.1 or newer is rarely tested.
+@item
+HP-UX 11.11 or newer is occasionally tested. HP-UX 11.00 is rarely tested.
+HP-UX 10.20 is rarely tested and low priority.
+@item
+IRIX 6.5 is occasionally tested. IRIX 5.3 is rarely tested and low priority.
+@item
+OSF/1 5.1 is occasionally tested. OSF/1 4.0 is rarely tested and low
+priority.
+@item
+Solaris 8 and newer are occasionally tested. Solaris 7 is rarely tested.
+Solaris 2.6 and older are rarely tested and low priority.
+@item
+Cygwin 1.7.x is frequently tested. Cygwin 1.5.x is occasionally tested.
+@item
+mingw is frequently tested. But note that some modules are currently
+unsupported on mingw: @code{mgetgroups}, @code{getugroups}, @code{idcache},
+@code{userspec}, @code{openpty}, @code{login_tty}, @code{forkpty},
+@code{pt_chown}, @code{grantpt}, @code{pty}, @code{savewd},
+@code{mkancesdirs}, @code{mkdir-p}, @code{euidaccess}, @code{faccessat}.
+The versions of Windows that are supported are Windows XP and newer.
+@item
+Native Windows, with MSVC as compiler, is not tested and low priority.
+@item
+mingw in 64-bit mode is not tested and low priority so far.
+@item
+Interix 6.1 is rarely tested, and requires the @code{suacomp} library
+(@url{http://sourceforge.net/projects/suacomp/}) in version 0.6.8 or newer.
+Interix 3.5 is not tested.
+@item
+Haiku is rarely tested, BeOS is not tested and low priority.
+@item
+uClibc on Linux is rarely tested.
+@item
+QNX is not tested and low priority.
+@end itemize
+
+Gnulib supports these operating systems only in an unvirtualized environment.
+When you run an OS inside a virtual machine, you have to be aware that the
+virtual machine can bring in bugs of its own. For example, floating-point
+operations on Solaris can behave slightly differently in QEMU than on real
+hardware. And Haiku's @command{bash} program misbehaves in VirtualBox 3,
+whereas it behaves fine in VirtualBox 4.
+
+Similarly, running native Windows binaries on GNU/Linux under WINE is
+rarely tested and low priority: WINE has a set of behaviours and bugs that
+is slightly different from native Windows.
+
+The following platforms are not supported by Gnulib. The cost of
+supporting them would exceed the benefit because they are rarely used, or
+poorly documented, or have been supplanted by other platforms, or diverge
+too much from POSIX, or some combination of these and other factors.
+Please don't bother sending us patches for them.
+
+@itemize
+@item
+Windows 95/98/ME.
+@item
+DJGPP and EMX (the 32-bit operating systems running in DOS).
+@item
+MSDOS (the 16-bit operating system).
+@item
+Windows Mobile, Symbian OS, iOS.
+@end itemize
+
@node Modules
@section Modules
For header files, such as @code{stdbool.h} or @code{stdint.h}, we provide
the substitute only if the system doesn't provide a correct one. The
template of this replacement is distributed in a slightly different name,
-with an added underscore, so that on systems which do provide a correct
+with @samp{.in} inserted before the @samp{.h} extension, so that on
+systems which do provide a correct
header file the system's one is used.
@subsection Enhancements of ISO C or POSIX functions
@subsection Interfaces to external libraries
Examples are the @samp{iconv} module, which interfaces to the
-@code{iconv()} facility, regardless whether it is contained in libc or in
+@code{iconv} facility, regardless whether it is contained in libc or in
an external @code{libiconv}. Or the @samp{readline} module, which
interfaces to the GNU readline library.
Documentation files are under this copyright:
@quotation
-Copyright @copyright{} 200X-200Y Free Software Foundation, Inc.@*
+Copyright @copyright{} 2004-200Y Free Software Foundation, Inc.@*
Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1 or
+under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
-Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
-Texts.
+Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
+copy of the license is included in the section entitled ``GNU Free
+Documentation License''.
@end quotation
@end table
If you want to use some Gnulib modules under LGPL, you can do so by
passing the option @samp{--lgpl} to @code{gnulib-tool}. This will
replace the GPL header with an LGPL header while copying the source
-files to your package.
+files to your package. Similarly, if you want some Gnulib modules
+under LGPLv2+ (Lesser GPL version 2.1 or newer), you can do so by
+passing the option @samp{--lgpl=2} to @code{gnulib-tool}.
Keep in mind that when you submit patches to files in Gnulib, you should
license them under a compatible license. This means that sometimes the
Gnulib modules are continually adapted, to match new practices, to be
consistent with newly added modules, or simply as a response to build
-failure reports. We don't make releases, but instead recommend to use the
-newest version of Gnulib from the Git repository, except in periods of major
-changes. The source tree can also be fetched from a read-only CVS that
-mirrors the Git repository.
+failure reports. Gnulib is available in two qualities:
+
+@itemize
+@item
+There is the newest version of Gnulib from the Git repository. The
+source tree can also be fetched from a read-only CVS that mirrors the Git
+repository.
+
+@item
+We also make stable releases every two months, at
+@url{http://erislabs.net/ianb/projects/gnulib/}.
+@end itemize
+
+If you are willing to report an occasional regression, we recommend to
+use the newest version always, except in periods of major changes. Most
+Gnulib users do this. If you prefer stable releases, please use the
+newest stable release.
@node Openness
@section Openness
@code{gnulib-tool}.
@end enumerate
-This is achieved by the @samp{--local-dir} option of @code{gnulib-tool}.
-
+This is achieved by the @samp{--local-dir} option of @code{gnulib-tool}
+(@pxref{Extending Gnulib}).
projects / gnulib.git / blobdiff