\input texinfo @c -*-texinfo-*-
-@comment $Id: gnulib.texi,v 1.5 2004-09-28 22:58:00 eggert Exp $
+@comment $Id: gnulib.texi,v 1.21 2006-04-30 13:38:54 karl Exp $
@comment %**start of header
@setfilename gnulib.info
@settitle GNU Gnulib
@syncodeindex pg cp
@comment %**end of header
-@set UPDATED $Date: 2004-09-28 22:58:00 $
+@set UPDATED $Date: 2006-04-30 13:38:54 $
@copying
This manual is for GNU Gnulib (updated @value{UPDATED}),
which is a library of common routines intended to be shared at the
source level.
-Copyright @copyright{} 2004 Free Software Foundation, Inc.
+Copyright @copyright{} 2004, 2005, 2006 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
@node Gnulib
@chapter Gnulib
-This is not a real manual. It's just a place to store random notes
-until someone (you?) gets around to actually writing a manual.
+This manual contains some bare-bones documentation, but not much more.
+It's mostly been a place to store notes until someone (you?)@ gets
+around to writing a coherent manual.
Getting started:
@menu
* Comments::
* Header files::
+* Quoting::
* ctime::
* inet_ntoa::
+* gcd::
* Out of memory handling::
+* Library version handling::
+* Regular expressions::
@end menu
+
@node Comments
@section Comments
any use. Thus, in theory, an application might not safely assume that
@code{_FOO_H} has not already been defined by a library. On the other
hand, using @code{FOO_H} will likely lead the higher risk of
-collisions with other symbols (e.g., @code{COFF_LONG_H} which is a CPP
-macro function). Your preference may depeend on whether you consider
+collisions with other symbols (e.g., @code{KEY_H}, @code{XK_H}, @code{BPF_H},
+which are CPP macro constants, or @code{COFF_LONG_H}, which is a CPP
+macro function). Your preference may depend on whether you consider
the header file under discussion as part of the application (which has
its own namespace for CPP symbols) or a supporting library (that
shouldn't interfere with the application's CPP symbol namespace).
your header file as something available for C programs only, or for C
and C++ programs alike.
-@node ctime
-@section ctime
-@findex ctime
+@subheading Include ordering
+
+When writing a gnulib module, or even in general, a good way to order
+the @samp{#include} directives is the following.
-The @code{ctime} function need not be reentrant, and consequently is
-not required to be thread safe. Implementations of @code{ctime}
-typically write the time stamp into static buffer. If two threads
-call @code{ctime} at roughly the same time, you might end up with the
-wrong date in one of the threads, or some undefined string. There is
-a re-entrant interface @code{ctime_r}, that take a pre-allocated
-buffer and length of the buffer, and return @code{NULL} on errors.
-The input buffer should be at least 26 bytes in size. The output
-string is locale-independent. However, years can have more than 4
-digits if @code{time_t} is sufficiently wide, so the length of the
-required output buffer is not easy to determine. Increasing the
-buffer size when @code{ctime_r} return @code{NULL} is not necessarily
-sufficient. The @code{NULL} return value could mean some other error
-condition, which will not go away by increasing the buffer size.
+@itemize
+@item First comes the #include "..." specifying the module being implemented.
+@item Then come all the #include <...> of system or system-replacement headers,
+in arbitrary order.
+@item Then come all the #include "..." of gnulib and private headers, in
+arbitrary order.
+@end itemize
-A more flexible function is @code{strftime}. However, note that it is
-locale dependent.
+@include quote.texi
-@node inet_ntoa
-@section inet_ntoa
-@findex inet_ntoa
+@include ctime.texi
-The @code{inet_ntoa} function need not be reentrant, and consequently
-is not required to be thread safe. Implementations of
-@code{inet_ntoa} typically write the time stamp into static buffer.
-If two threads call @code{inet_ntoa} at roughly the same time, you
-might end up with the wrong date in one of the threads, or some
-undefined string. Further, @code{inet_ntoa} is specific for
-@acronym{IPv4} addresses.
+@include gcd.texi
-A protocol independent function is @code{inet_ntop}.
+@include inet_ntoa.texi
@node Out of memory handling
fail.
-@node Invoking gnulib-tool
-@chapter Invoking gnulib-tool
-
-@pindex gnulib-tool
-@cindex invoking @command{gnulib-tool}
-
-Run @samp{gnulib-tool --help}, and use the source.
-@command{gnulib-tool} is the way to import Gnulib modules.
-
-@menu
-* Initial import:: First import of Gnulib modules.
-* Importing updated files:: Subsequent imports.
-* Finishing touches:: Simplifying imports.
-@end menu
-
-
-@node Initial import
-@section Initial import
-@cindex initial import
-
-Gnulib assumes your project uses Autoconf and Automake. Invoking
-@samp{gnulib-tool --import} will copy source files, create a
-@file{Makefile.am} to build them, and generate a @file{gnulib.m4} with
-Autoconf M4 macro declarations used by @file{configure.ac}.
-
-Our example will be a library that uses Autoconf, Automake and
-Libtool. It calls @code{strdup}, and you wish to use gnulib to make
-the package portable to C89 (which doesn't have @code{strdup}).
-
-@example
-~/src/libfoo$ gnulib-tool --import strdup
-Module list with included dependencies:
- strdup
-File list:
- lib/strdup.c
- lib/strdup.h
- m4/onceonly_2_57.m4
- m4/strdup.m4
-Creating ./lib/Makefile.am...
-Creating ./m4/gnulib.m4...
-Finished.
-
-Don't forget to add "lib/Makefile"
-to AC_CONFIG_FILES in "./configure.ac" and to mention
-"lib" in SUBDIRS in some Makefile.am.
-~/src/libfoo$
-@end example
+@node Library version handling
+@section Library version handling
-By default, the source code is copied into @file{lib/} and the M4
-macros in @file{m4/}. You can override these paths by using
-@code{--source-base=DIRECTORY} and @code{--m4-base=DIRECTORY}, or by
-adding @samp{gl_SOURCE_BASE(DIRECTORY)} and
-@samp{gl_M4_BASE(DIRECTORY)} to your @file{configure.ac}.
-
-@code{gnulib-tool} will overwrite any pre-existing files, in
-particular @file{Makefile.am}. Unfortunately, separating the
-generated @file{Makefile.am} content (for building the gnulib library)
-into a separate file, say @file{gnulib.mk}, that could be included
-by your handwritten @file{Makefile.am} is not possible, due to how
-variable assignments are handled by Automake.
-
-Consequently, it can be a good idea to chose directories that are not
-already used by your projects, to separate gnulib imported files from
-your own files. This approach can also be useful if you want to avoid
-conflicts between other tools (e.g., @code{getextize} that also copy
-M4 files into your package. Simon Josefsson successfully uses a source
-base of @file{gl/}, and a M4 base of @file{gl/m4/}, in several
-packages.
-
-A few manual steps are required to finish the initial import.
-
-First, you need to make sure Autoconf can find the macro definitions
-in @file{gnulib.m4}. Use the @code{ACLOCAL_AMFLAGS} specifier in your
-top-level @file{Makefile.am} file, as in:
-
-@example
-ACLOCAL_AMFLAGS = -I m4
-@end example
-
-Naturally, replace @file{m4} with the value from @code{--m4-base} or
-@code{gl_M4_BASE}. If the M4 base is @file{gl/m4} you would use:
-
-@example
-ACLOCAL_AMFLAGS = -I gl/m4
-@end example
-
-You are now ready to call the M4 macros in @code{gnulib.m4} from
-@file{configure.ac}. The macro @code{gl_EARLY} must be called as soon
-as possible after verifying that the C compiler is working.
-Typically, this is immediately after @code{AC_PROG_CC}, as in:
+The module @samp{check-version} can be useful when your gnulib
+application is a system library. You will typically wrap the call to
+the @code{check_version} function through a library API, your library
+header file may contain:
@example
+#define STRINGPREP_VERSION "0.5.18"
...
-AC_PROG_CC
-gl_EARLY
-...
+ extern const char *stringprep_check_version (const char *req_version);
@end example
-The core part of the gnulib checks are done by the macro
-@code{gl_INIT}. Place it further down in the file, typically where
-you normally check for header files or functions. Or in a separate
-section with other gnulib statements, such as @code{gl_SOURCE_BASE}.
-For example:
+To avoid ELF symbol collisions with other libraries that use the
+@samp{check-version} module, add to @file{config.h} through a
+AC_DEFINE something like:
@example
-...
-# For gnulib.
-gl_INIT
-...
+AC_DEFINE(check_version, stringprep_check_version, [Rename check_version.])
@end example
-You must also make sure that the gnulib library is built. Add the
-@code{Makefile} in the gnulib source base directory to
-@code{AC_CONFIG_FILES}, as in:
+The @code{stringprep_check_version} function will thus be implemented
+by the @code{check_version} module.
-@example
-AC_CONFIG_FILES(... lib/Makefile ...)
-@end example
-
-If your gnulib source base is @file{gl}, you would use:
+There are two uses of the interface. The first is a way to provide
+for applications to find out the version number of the library it
+uses. The application may contain diagnostic code such as:
@example
-AC_CONFIG_FILES(... gl/Makefile ...)
+ printf ("Stringprep version: header %s library %s",
+ STRINGPREP_VERSION,
+ stringprep_check_version (NULL));
@end example
-You must also make sure that @code{make} work in the gnulib directory.
-Add the gnulib source base directory to a @code{SUBDIRS} Makefile.am
-statement, as in:
+Separating the library and header file version can be useful when
+searching for version mismatch related problems.
-@example
-SUBDIRS = lib
-@end example
-
-or if you, more likely, already have a few entries in @code{SUBDIRS},
-you can add something like:
-
-@example
-SUBDIRS += lib
-@end example
-
-If you are using a gnulib source base of @code{gl}, you would use:
-
-@example
-SUBDIRS += gl
-@end example
-
-Finally, you have add C flags and LD flags, so that you can make use
-of the gnulib library. For example:
-
-@example
-...
-AM_CPPFLAGS = -I$(top_srcdir)/lib
-...
-LIBADD = lib/libgnu.la
-...
-@end example
-
-Don't forget to @code{#include} the various header files. In this
-example, you would need to make sure that @samp{#include <strdup.h>}
-is evaluated when compiling all source code files, that want to make
-use of @code{strdup}.
-
-
-@node Importing updated files
-@section Importing updated files
+The second uses is as a rudimentary test of proper library version, by
+making sure the application get a library version that is the same, or
+newer, than the header file used when building the application. This
+doesn't catch all problems, libraries may change backwards incompatibly
+in later versions, but enable applications to require a certain
+minimum version before it may proceed.
-From time to time, you may want to invoke @samp{gnulib-tool --import}
-to update the files in your package. Once you have set up your
-package for gnulib, this step is quite simple. For example:
+Typical uses look like:
@example
-~/src/libfoo$ gnulib-tool --import --source-base gl --m4-base gl/m4 strdup
-Module list with included dependencies:
- strdup
-File list:
- lib/strdup.c
- lib/strdup.h
- m4/onceonly_2_57.m4
- m4/strdup.m4
-Creating ./lib/Makefile.am...
-Creating ./m4/gnulib.m4...
-Finished.
-
-Don't forget to add "lib/Makefile"
-to AC_CONFIG_FILES in "./configure.ac" and to mention
-"lib" in SUBDIRS in some Makefile.am.
-~/src/libfoo$
+ /* Check version of libgcrypt. */
+ if (!gcry_check_version (GCRYPT_VERSION))
+ die ("version mismatch\n");
@end example
-If you don't recall how you invoked the tool last time, the commands
-used (and the operations it resulted in) are placed in comments within
-the generated @file{Makefile.am} and @file{gnulib.m4}, as in:
-@example
-...
-# Invoked as: gnulib-tool --import strdup
-# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --libtool strdup
-...
-@end example
+@node Regular expressions
+@section Regular expressions
+Gnulib supports many different types of regular expressions; although
+the underlying features are the same or identical, the syntax used
+varies. The descriptions given here for the different types are
+generated automatically.
-@node Finishing touches
-@section Finishing touches
-
-Invoking @samp{gnulib-tool --import} with the proper parameters (e.g.,
-@samp{--m4-base gl/m4}) and list of modules (e.g., @samp{strdup
-snprintf getline minmax}) can be tedious. To simplify this procedure,
-you may put the command line parameters in your @file{configure.ac}.
-For example:
-
-@example
-...
-AC_PROG_CC
-gl_EARLY
-...
-# For gnulib.
-gl_SOURCE_BASE(gl)
-gl_M4_BASE(gl/m4)
-gl_LIB(libgl)
-gl_MODULES(getopt progname strdup dummy exit error getpass-gnu getaddrinfo)
-gl_INIT
-...
-@end example
+@include regexprops-generic.texi
-This illustrate all macros defined in @file{gnulib.m4}. With the
-above, importing new files are as simple as running @samp{gnulib-tool
---import} with no additional parameters.
-The macros @code{gl_EARLY}, @code{gl_INIT}, @code{gl_SOURCE_BASE}, and
-@code{gl_M4_BASE} have been discussed earlier. The @code{gl_LIB}
-macro can be used if you wish to change the library name (by default
-@file{libgnu.a} or @file{libgnu.la} if you use libtool). The
-@code{gl_MODULES} macro is used to specify which modules to import.
+@include gnulib-tool.texi
@node Copying This Manual
projects / gnulib.git / blobdiff