\input texinfo @c -*-texinfo-*-
-@comment $Id: gnulib.texi,v 1.8 2005-05-19 13:17:34 karl Exp $
+@comment $Id: gnulib.texi,v 1.14 2005-07-27 00:16:01 karl Exp $
@comment %**start of header
@setfilename gnulib.info
@settitle GNU Gnulib
@syncodeindex pg cp
@comment %**end of header
-@set UPDATED $Date: 2005-05-19 13:17:34 $
+@set UPDATED $Date: 2005-07-27 00:16:01 $
@copying
This manual is for GNU Gnulib (updated @value{UPDATED}),
@chapter Gnulib
This manual contains some bare-bones documentation, but not much more.
-It's mostly been a place to store notes until someone (you?) gets
+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::
* Out of memory handling::
+* Library version handling::
+* Regular expressions::
@end menu
+
@node Comments
@section Comments
your header file as something available for C programs only, or for C
and C++ programs alike.
+@subheading Include ordering
+
+When writing a gnulib module, or even in general, a good way to order
+the @samp{#include} directives is the following.
+
+@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
+
+
+@node Quoting
+@section Quoting
+
+@cindex Quoting
+@findex quote
+@findex quotearg
+
+Gnulib provides @samp{quote} and @samp{quotearg} modules to help with
+quoting text, such as file names, in messages to the user. Here's an
+example of using @samp{quote}:
+
+@example
+#include <quote.h>
+ ...
+ error (0, errno, _("cannot change owner of %s"), quote (fname));
+@end example
+
+This differs from
+
+@example
+ error (0, errno, _("cannot change owner of `%s'"), fname);
+@end example
+
+@noindent in that @code{quote} escapes unusual characters in
+@code{fname}, e.g., @samp{'} and control characters like @samp{\n}.
+
+@findex quote_n
+However, a caveat: @code{quote} reuses the storage that it returns.
+Hence if you need more than one thing quoted at the same time, you
+need to use @code{quote_n}.
+
+@findex quotearg_alloc
+Also, the quote module is not suited for multithreaded applications.
+In that case, you have to use @code{quotearg_alloc}, defined in the
+@samp{quotearg} module, which is decidedly less convenient.
+
+
@node ctime
@section ctime
@findex ctime
fail.
+@node Library version handling
+@section Library version handling
+
+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"
+...
+ extern const char *stringprep_check_version (const char *req_version);
+@end 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
+AC_DEFINE(check_version, stringprep_check_version, [Rename check_version.])
+@end example
+
+The @code{stringprep_check_version} function will thus be implemented
+by the @code{check_version} module.
+
+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
+ printf ("Stringprep version: header %s library %s",
+ STRINGPREP_VERSION,
+ stringprep_check_version (NULL));
+@end example
+
+Separating the library and header file version can be useful when
+searching for version mismatch related problems.
+
+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.
+
+Typical uses look like:
+
+@example
+ /* Check version of libgcrypt. */
+ if (!gcry_check_version (GCRYPT_VERSION))
+ die ("version mismatch\n");
+@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.
+
+@include regexprops-generic.texi
+
+
@node Invoking gnulib-tool
@chapter Invoking gnulib-tool
...
@end example
+@code{gl_INIT} will in turn call the macros related with the
+gnulib functions, be it specific gnulib macros, like @code{gl_FUNC_ALLOCA}
+or autoconf or automake macro like @code{AC_FUNC_ALLOCA} or
+@code{AM_FUNC_GETLINE} so there is no need to call those macros yourself
+when you use the corresponding gnulib modules.
+
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:
@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>}
+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}.
-
+use of @code{strdup}.
+
+When an include file is provided by the gnulib
+you shouldn't try to include the corresponding system header files
+yourself but let the gnulib header file do it as the ordering
+of the definition for some symbols may be significant.
+
+For example, to use the @code{time_r} gnulib module you should
+use include header file provided by the gnulib, and so
+@samp{#include "time_r.h"}, but you shouldn't explicitely
+@samp{#include <time.h>} as it is already done in @file{time_r.h}
+before the redefinition of some symbols.
@node Importing updated files
@section Importing updated files
projects / gnulib.git / blobdiff