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16. Using the library

This chapter explains some practical considerations, regarding the installation and compiler options that are needed in order to use this library.

16.1 Installation

Before you can use the library, it must be installed. First, you have to make sure all dependencies are installed. They are listed in the file ‘DEPENDENCIES’.

Then you can proceed to build and install the library, as described in the file ‘INSTALL’. For installation on Windows systems, please refer to the file ‘README.windows’.

16.2 Compiler options

Let's denote as LIBUNISTRING_PREFIX the value of the ‘--prefix’ option that you passed to configure while installing this package. If you didn't pass any ‘--prefix’ option, then the package is installed in ‘/usr/local’.

Let's denote as LIBUNISTRING_INCLUDEDIR the directory where the include files were installed. This is usually the same as ${LIBUNISTRING_PREFIX}/include. Except that if you passed an ‘--includedir’ option to configure, it is the value of that option.

Let's further denote as LIBUNISTRING_LIBDIR the directory where the library itself was installed. This is the value that you passed with the ‘--libdir’ option to configure, or otherwise the same as ${LIBUNISTRING_PREFIX}/lib. Recall that when building in 64-bit mode on a 64-bit GNU/Linux system that supports executables in either 64-bit mode or 32-bit mode, you should have used the option --libdir=${LIBUNISTRING_PREFIX}/lib64.

So that the compiler finds the include files, you have to pass it the option -I${LIBUNISTRING_INCLUDEDIR}.

So that the compiler finds the library during its linking pass, you have to pass it the options -L${LIBUNISTRING_LIBDIR} -lunistring. On some systems, in some configurations, you also have to pass options needed for linking with libiconv. The autoconf macro gl_LIBUNISTRING (see Autoconf macro) deals with this particularity.

16.3 Include files

Most of the include files have been presented in the introduction, see Introduction, and subsequent detailed chapters.

Another include file is <unistring/version.h>. It contains the version number of the libunistring library.


This constant contains the version of libunistring that is being used at compile time. It encodes the major and minor parts of the version number only. These parts are encoded in the form (major<<8) + minor.

Constant: int _libunistring_version

This constant contains the version of libunistring that is being used at run time. It encodes the major and minor parts of the version number only. These parts are encoded in the form (major<<8) + minor.

It is possible that _libunistring_version is greater than _LIBUNISTRING_VERSION. This can happen when you use libunistring as a shared library, and a newer, binary backward-compatible version has been installed after your program that uses libunistring was installed.

16.4 Autoconf macro

GNU Gnulib provides an autoconf macro that tests for the availability of libunistring. It is contained in the Gnulib module ‘libunistring’, see http://www.gnu.org/software/gnulib/MODULES.html#module=libunistring.

The macro is called gl_LIBUNISTRING. It searches for an installed libunistring. If found, it sets and AC_SUBSTs HAVE_LIBUNISTRING=yes and the LIBUNISTRING and LTLIBUNISTRING variables and augments the CPPFLAGS variable, and defines the C macro HAVE_LIBUNISTRING to 1. Otherwise, it sets and AC_SUBSTs HAVE_LIBUNISTRING=no and LIBUNISTRING and LTLIBUNISTRING to empty.

The complexities that gl_LIBUNISTRING deals with are the following:

16.5 Reporting problems

If you encounter any problem, please don't hesitate to send a detailed bug report to the bug-libunistring@gnu.org mailing list. You can alternatively also use the bug tracker at the project page https://savannah.gnu.org/projects/libunistring.

Please always include the version number of this library, and a short description of your operating system and compilation environment with corresponding version numbers.

For problems that appear while building and installing libunistring, for which you don't find the remedy in the ‘INSTALL’ file, please include a description of the options that you passed to the ‘configure’ script.

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