@node Portability and Application Code
@section Portability and Application Code
-One of the goals of Gnulib is to make portable programming easy, on the
-basis of the standards relevant for Unix. The objective behind that is to
-avoid a fragmentation of the user community into disjoint user communities
-according to the operating system, and instead allow synergies between
-users on different operating systems.
+One of the goals of Gnulib is to make portable programming easy, on
+the basis of the standards relevant for GNU (and Unix). The objective
+behind that is to avoid a fragmentation of the user community into
+disjoint user communities according to the operating system, and
+instead allow synergies between users on different operating systems.
Another goal of Gnulib is to provide application code that can be shared
between several applications. Some people wonder: "What? glibc doesn't
There is no clear borderline between both areas.
For example, Gnulib has a facility for generating the name of backup
-files. While this task is an applicative one -- no standard specifies an
-API for it --, the na@"ive code has some portability problems because on
-some platforms the length of file name components is limited to 30
-characters or so. Gnulib handles that.
-
-Similarly, Gnulib has a facility for executing a command in a subprocess.
-It is at the same time a portability enhancement (it works on Unix and
-Windows, compared to the classical @code{fork()}/@code{exec()} 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.
+files. While this task is entirely at the application level --- no
+standard specifies an API for it --- the na@"{@dotless{i}}ve code has
+some portability problems because on some platforms the length of file
+name components is limited to 30 characters or so. Gnulib handles
+that.
+
+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
+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 Modules
@section Modules
Gnulib is divided into modules. Every module implements a single
-facility. Modules can depend on other modules.
+facility. Modules can depend on other modules.
A module consists of a number of files and a module description. The
files are copied by @code{gnulib-tool} into the package that will use it,
the @file{m4/} subdirectory. Build scripts reside in the
@file{build-aux/} subdirectory.
-The module description contains the list of files -- @code{gnulib-tool}
-copies these files. It contains the module's dependencies --
-@code{gnulib-tool} installs them as well. It also contains the autoconf
-macro invocation (usually a single line or nothing at all) --
-@code{gnulib-tool} ensures this is invoked from the package's
-@file{configure.ac} file. And also a @file{Makefile.am} snippet --
-@code{gnulib-tool} collects these into a @file{Makefile.am} for the
-tailored Gnulib part. The module description and include file
+The module description contains the list of files --- @code{gnulib-tool}
+copies these files. It contains the module's
+dependencies --- @code{gnulib-tool} installs them as well. It also
+contains the autoconf macro invocation (usually a single line or
+nothing at all) --- @code{gnulib-tool} ensures this is invoked from the
+package's @file{configure.ac} file. And also a @file{Makefile.am}
+snippet --- @code{gnulib-tool} collects these into a @file{Makefile.am}
+for the tailored Gnulib part. The module description and include file
specification are for documentation purposes; they are combined into
@file{MODULES.html}.
@item
It ensures consistency of the used autoconf macros and @file{Makefile.am}
rules with the source code. For example, source code which uses the
-@code{getopt_long} function -- this is a common way to implement parsing
-of command line options in a way that complies with the GNU standards --
+@code{getopt_long} function --- this is a common way to implement parsing
+of command line options in a way that complies with the GNU standards ---
needs the source code (@file{lib/getopt.c} and others), the autoconf macro
which detects whether the system's libc already has this function (in
@file{m4/getopt.m4}), and a few @file{Makefile.am} lines that create the
@subsection Enhancements of ISO C or POSIX functions
These are sometimes POSIX functions with GNU extensions also found in
-glibc -- examples: @samp{getopt}, @samp{fnmatch} --, and often new APIs
--- for example, for all functions that allocate memory in one way or the
-other, we have variants which also include the error checking against the
-out-of-memory condition.
+glibc --- examples: @samp{getopt}, @samp{fnmatch} --- and often new
+APIs --- for example, for all functions that allocate memory in one way
+or the other, we have variants which also include the error checking
+against the out-of-memory condition.
@subsection Portable general use facilities
-Examples are a module for copying a file -- the portability problems
-relate to the copying of the file's modification time, access rights, and
-extended attributes -- or a module for extracting the tail component of a
-file name -- here the portability to Woe32 requires a different API than
-the classical POSIX @code{basename} function.
+Examples are a module for copying a file --- the portability problems
+relate to the copying of the file's modification time, access rights,
+and extended attributes --- or a module for extracting the tail
+component of a file name --- here the portability to Woe32 requires a
+different API than the classical POSIX @code{basename} function.
@subsection Reusable application code
@node Copyright
@section Copyright
-Most modules are under the GPL. Some -- mostly modules which can
-reasonably be used in libraries -- are under LGPL. The source files
+Most modules are under the GPL. Some, mostly modules which can
+reasonably be used in libraries, are under LGPL. The source files
always say "GPL", but the real license specification is in the module
description file.
+More precisely, the license specification in the module description
+file applies to the files in @file{lib/} and @file{build-aux/}. Different
+licenses apply to files in special directories:
+
+@table @file
+@item modules/
+Module description files are under this copyright:
+
+@quotation
+Copyright @copyright{} 200X-200Y Free Software Foundation, Inc.@*
+Copying and distribution of this file, with or without modification,
+in any medium, are permitted without royalty provided the copyright
+notice and this notice are preserved.
+@end quotation
+
+@item m4/
+Autoconf macro files are under this copyright:
+
+@quotation
+Copyright @copyright{} 200X-200Y Free Software Foundation, Inc.@*
+This file is free software; the Free Software Foundation
+gives unlimited permission to copy and/or distribute it,
+with or without modifications, as long as this notice is preserved.
+@end quotation
+
+@item tests/
+If a license statement is not present in a test module, the test files are
+under GPL. Even if the corresponding source module is under LGPL, this is
+not a problem, since compiled tests are not installed by ``make install''.
+
+@item doc/
+Documentation files are under this copyright:
+
+@quotation
+Copyright @copyright{} 200X-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
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.
+@end quotation
+@end table
+
If you want to use some Gnulib modules under LGPL, you can do so by
-passing the option --lgpl to @code{gnulib-tool}. This will replace the
-GPL header with an LGPL header while copying the source files to your
-package.
+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.
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
projects / gnulib.git / blobdiff