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The AM_GNU_GETTEXT
macro tests for the presence of the GNU gettext
function family in either the C library or a separate libintl
library (shared or static libraries are both supported). It also invokes
AM_PO_SUBDIRS
, thus preparing the po/ directories of the
package for building.
AM_GNU_GETTEXT
accepts up to two optional arguments. The general
syntax is
AM_GNU_GETTEXT([intlsymbol], [needsymbol])
intlsymbol should always be ‘external’.
If needsymbol is specified and is ‘need-ngettext’, then GNU
gettext implementations (in libc or libintl) without the ngettext()
function will be ignored. If needsymbol is specified and is
‘need-formatstring-macros’, then GNU gettext implementations that don’t
support the ISO C 99 <inttypes.h> formatstring macros will be ignored.
Only one needsymbol can be specified. These requirements can also be
specified by using the macro AM_GNU_GETTEXT_NEED
elsewhere. To specify
more than one requirement, just specify the strongest one among them, or
invoke the AM_GNU_GETTEXT_NEED
macro several times. The hierarchy
among the various alternatives is as follows: ‘need-formatstring-macros’
implies ‘need-ngettext’.
The AM_GNU_GETTEXT
macro determines whether GNU gettext is
available and should be used. If so, it sets the USE_NLS
variable
to ‘yes’; it defines ENABLE_NLS
to 1 in the autoconf
generated configuration file (usually called config.h); it sets
the variables LIBINTL
and LTLIBINTL
to the linker options
for use in a Makefile (LIBINTL
for use without libtool,
LTLIBINTL
for use with libtool); it adds an ‘-I’ option to
CPPFLAGS
if necessary. In the negative case, it sets
USE_NLS
to ‘no’; it sets LIBINTL
and LTLIBINTL
to empty and doesn’t change CPPFLAGS
.
The complexities that AM_GNU_GETTEXT
deals with are the following:
gettext
in the C library, for example
glibc. Some have it in a separate library libintl
. GNU libintl
might have been installed as part of the GNU gettext
package.
libintl
, if installed, is not necessarily already in the search
path (CPPFLAGS
for the include file search path, LDFLAGS
for
the library search path).
gettext
cannot exploit the GNU mo files, doesn’t have the
necessary locale dependency features, and cannot convert messages from
the catalog’s text encoding to the user’s locale encoding.
libintl
, if installed, is not necessarily already in the
run time library search path. To avoid the need for setting an environment
variable like LD_LIBRARY_PATH
, the macro adds the appropriate
run time search path options to the LIBINTL
and LTLIBINTL
variables. This works on most systems, but not on some operating systems
with limited shared library support, like SCO.
libintl
relies on POSIX/XSI iconv
. The macro checks for
linker options needed to use iconv and appends them to the LIBINTL
and LTLIBINTL
variables.
Additionally, the AM_GNU_GETTEXT
macro sets two variables, for
convenience. Both are derived from the --localedir
configure
option. They are correct even on native Windows, where directories
frequently contain backslashes.
localedir_c
This is the value of localedir
, in C syntax. This variable is
meant to be substituted into C or C++ code through
AC_CONFIG_FILES
.
localedir_c_make
This is the value of localedir
, in C syntax, escaped for use in
a Makefile
. This variable is meant to be used in Makefiles,
for example for defining a C macro named LOCALEDIR
:
AM_CPPFLAGS = ... -DLOCALEDIR=$(localedir_c_make) ...