File: gettext.info,  Node: AM_GNU_GETTEXT,  Next: AM_GNU_GETTEXT_VERSION,  Up: autoconf macros

14.5.1 AM_GNU_GETTEXT in ‘gettext.m4’
-------------------------------------

   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 ‘’ 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:

   • Some operating systems have ‘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.

   • GNU ‘libintl’, if installed, is not necessarily already in the
     search path (‘CPPFLAGS’ for the include file search path, ‘LDFLAGS’
     for the library search path).

   • Except for glibc and the Solaris 11 libc, the operating system's
     native ‘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.

   • GNU ‘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.

   • GNU ‘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) ...