This file documents the installation of Octave.

   Octave is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation.

   *Note*: This file is automatically generated from
'doc/interpreter/install.txi' in the Octave sources.  To update the
documentation make changes to the .txi source file rather than this
derived file.

1 Installing Octave
*******************

The procedure for installing Octave from source on a Unix-like system is
described next.  Building on other platforms will follow similar steps.
Note that this description applies to Octave releases.  Building the
development sources from the Mercurial archive requires additional steps
as described in the development source itself.

1.1 Build Dependencies
======================

Octave is a fairly large program with many build dependencies.  You may
be able to find pre-packaged versions of the dependencies distributed as
part of your system, or you may have to build some or all of them
yourself.

1.1.1 Obtaining the Dependencies Automatically
----------------------------------------------

On some systems you can obtain many of Octave's build dependencies
automatically.  The commands for doing this vary by system.  Similarly,
the names of pre-compiled packages vary by system and do not always
match exactly the names listed in *note Build Tools:: and *note External
Packages::.

   You will usually need the development version of an external
dependency so that you get the libraries and header files for building
software, not just for running already compiled programs.  These
packages typically have names that end with the suffix '-dev' or
'-devel'.

   On systems with 'apt-get' (Debian, Ubuntu, etc.), you may be able to
install most of the tools and external packages using a command similar
to

     apt-get build-dep octave

The specific package name may be 'octave3.2' or 'octave3.4'.  The set of
required tools and external dependencies does not change frequently, so
it is not important that the version match exactly, but you should use
the most recent one available.

   On systems with 'yum' (Fedora, Red Hat, etc.), you may be able to
install most of the tools and external packages using a command similar
to

     yum-builddep octave

The 'yum-builddep' utility is part of the 'yum-utils' package.

   For either type of system, the package name may include a version
number.  The set of required tools and external dependencies does not
change frequently, so it is not important that the version exactly match
the version you are installing, but you should use the most recent one
available.

1.1.2 Build Tools
-----------------

The following tools are required:

C++, C, and Fortran compilers
     The Octave sources are primarily written in C++, but some portions
     are also written in C and Fortran.  The Octave sources are intended
     to be portable.  Recent versions of the GNU compiler collection
     (GCC) should work (<https://gcc.gnu.org>).  If you use GCC, you
     should avoid mixing versions.  For example, be sure that you are
     not using the obsolete 'g77' Fortran compiler with modern versions
     of 'gcc' and 'g++'.

GNU Make
     Tool for building software (<https://www.gnu.org/software/make>).
     Octave's build system requires GNU Make.  Other versions of Make
     will not work.  Fortunately, GNU Make is highly portable and easy
     to install.

AWK, sed, and other Unix utilities
     Basic Unix system utilities are required for building Octave.  All
     will be available with any modern Unix system and also on Windows
     with either Cygwin or MinGW and MSYS.

   Additionally, the following tools may be needed:

Bison
     Parser generator (<https://www.gnu.org/software/bison>).  You will
     need Bison if you modify the 'oct-parse.yy' source file or if you
     delete the files that are generated from it.

Flex
     Lexer analyzer (<https://www.gnu.org/software/flex>).  You will
     need Flex if you modify the 'lex.ll' source file or if you delete
     the files that are generated from it.

Autoconf
     Package for software configuration
     (<https://www.gnu.org/software/autoconf>).  Autoconf is required if
     you modify Octave's 'configure.ac' file or other files that it
     requires.

Automake
     Package for Makefile generation
     (<https://www.gnu.org/software/automake>).  Automake is required if
     you modify Octave's 'Makefile.am' files or other files that they
     depend on.

Libtool
     Package for building software libraries
     (<https://www.gnu.org/software/libtool>).  Libtool is required by
     Automake.

gperf
     Perfect hash function generator
     (<https://www.gnu.org/software/gperf>).  You will need gperf if you
     modify the 'octave.gperf' file or if you delete the file that is
     generated from it.

Texinfo
     Package for generating online and print documentation
     (<https://www.gnu.org/software/texinfo>).  You will need Texinfo to
     build Octave's documentation or if you modify the documentation
     source files or the docstring of any Octave function.

1.1.3 External Packages
-----------------------

The following external packages are required:

BLAS
     Basic Linear Algebra Subroutine library.  Accelerated BLAS
     libraries such as OpenBLAS (<https://www.openblas.net/>) or ATLAS
     (<http://math-atlas.sourceforge.net>) are recommended for best
     performance.  The reference implementation
     (<http://www.netlib.org/blas>) is slow, unmaintained, and suffers
     from certain bugs in corner case inputs.

LAPACK
     Linear Algebra Package (<http://www.netlib.org/lapack>).

PCRE
     The Perl Compatible Regular Expression library
     (<https://www.pcre.org>).

   The following external package is optional but strongly recommended:

GNU Readline
     Command-line editing library (<https://www.gnu.org/s/readline>).

   If you wish to build Octave without GNU readline installed, you must
use the '--disable-readline' option when running the configure script.

   The following external software packages are optional but
recommended:

ARPACK
     Library for the solution of large-scale eigenvalue problems
     (<https://forge.scilab.org/index.php/p/arpack-ng>).  ARPACK is
     required to provide the functions 'eigs' and 'svds'.

cURL
     Library for transferring data with URL syntax
     (<https://curl.haxx.se>).  cURL is required to provide the
     'urlread' and 'urlwrite' functions and the 'ftp' class.

FFTW3
     Library for computing discrete Fourier transforms
     (<http://www.fftw.org>).  FFTW3 is used to provide better
     performance for functions that compute discrete Fourier transforms
     ('fft', 'ifft', 'fft2', etc.)

FLTK
     Portable GUI toolkit (<http://www.fltk.org>).  FLTK can be used to
     provide windows for Octave's OpenGL-based graphics functions.

fontconfig
     Library for configuring and customizing font access
     (<https://www.freedesktop.org/wiki/Software/fontconfig>).
     Fontconfig is used to manage fonts for Octave's OpenGL-based
     graphics functions.

FreeType
     Portable font engine (<https://www.freetype.org>).  FreeType is
     used to perform font rendering for Octave's OpenGL-based graphics
     functions.

GLPK
     GNU Linear Programming Kit (<https://www.gnu.org/software/glpk>).
     GPLK is required for the function 'glpk'.

gl2ps
     OpenGL to PostScript printing library
     (<https://www.geuz.org/gl2ps/>).  gl2ps is required for printing
     when using OpenGL-based graphics toolkits (currently either FLTK or
     Qt).

gnuplot
     Interactive graphics program (<http://www.gnuplot.info>).  gnuplot
     can be used as a graphics renderer for Octave; prior to Octave 4.0,
     gnuplot was the default graphics renderer.

GraphicsMagick++
     Image processing library (<http://www.graphicsmagick.org>).
     GraphicsMagick++ is used to provide the 'imread' and 'imwrite'
     functions.

HDF5
     Library for manipulating portable data files
     (<https://www.hdfgroup.org/HDF5>).  HDF5 is required for Octave's
     'load' and 'save' commands to read and write HDF data files.

Java Development Kit
     Java programming language compiler and libraries.  The OpenJDK free
     software implementation is recommended
     (<http://openjdk.java.net/>), although other JDK implementations
     may work.  Java is required to be able to call Java functions from
     within Octave.

LLVM
     Compiler framework, (<https://www.llvm.org>).  LLVM is required for
     Octave's experimental just-in-time (JIT) compilation for speeding
     up the interpreter.

OpenGL
     API for portable 2-D and 3-D graphics (<https://www.opengl.org>).
     An OpenGL implementation can be used to provide a renderer for
     Octave's graphics functions.  Octave's OpenGL-based graphics
     functions usually outperform the gnuplot-based graphics functions
     because plot data can be rendered directly instead of sending data
     and commands to gnuplot for interpretation and rendering.  Since
     Octave 4.0, the default graphics renderer ("qt") has been
     OpenGL-based.

PortAudio
     PortAudio (<http://www.portaudio.com/>) provides a very simple API
     for recording and/or playing sound using a simple callback function
     or a blocking read/write interface.  It is required for the audio
     processing functions 'audioplayer', 'audiorecorder', and
     'audiodevinfo'.

Qhull
     Computational geometry library (<http://www.qhull.org>).  Qhull is
     required to provide the functions 'convhull', 'convhulln',
     'delaunay', 'delaunayn', 'voronoi', and 'voronoin'.

QRUPDATE
     QR factorization updating library
     (<https://sourceforge.net/projects/qrupdate>).  QRUPDATE is used to
     provide improved performance for the functions 'qrdelete',
     'qrinsert', 'qrshift', and 'qrupdate'.

QScintilla
     Source code highlighter and manipulator; a Qt port of Scintilla
     (<http://www.riverbankcomputing.co.uk/software/qscintilla>).
     QScintilla is used for syntax highlighting and code completion in
     the GUI.

Qt
     GUI and utility libraries (<https://www.qt.io>).  Qt is required
     for building the GUI.  It is a large framework, but the only
     components required are the GUI, core, and network modules.  Since
     Octave 4.0, the default graphics renderer ("qt") has been Qt-based,
     which has been OpenGL-based.

SuiteSparse
     Sparse matrix factorization library
     (<http://faculty.cse.tamu.edu/davis/suitesparse.html>).
     SuiteSparse is required to provide sparse matrix factorizations and
     solution of linear equations for sparse systems.

SUNDIALS
     The SUite of Nonlinear and DIfferential/ALgebraic Equation Solvers
     (<https://computation.llnl.gov/projects/sundials>) is required for
     the Ordinary Differential Equations (ODE) solvers 'ode15i' and
     'ode15s'.

zlib
     Data compression library (<https://zlib.net>).  The zlib library is
     required for Octave's 'load' and 'save' commands to handle
     compressed data, including MATLAB v5 MAT files.

1.2 Running Configure and Make
==============================

   * Run the shell script 'configure'.  This will determine the features
     your system has (or doesn't have) and create a file named
     'Makefile' from each of the files named 'Makefile.in'.

     Here is a summary of the configure options that are most frequently
     used when building Octave:

     '--help'
          Print a summary of the options recognized by the configure
          script.

     '--prefix=PREFIX'
          Install Octave in subdirectories below PREFIX.  The default
          value of PREFIX is '/usr/local'.

     '--srcdir=DIR'
          Look for Octave sources in the directory DIR.

     '--disable-64'
          Disable using 64-bit integers for indexing arrays and use
          32-bit integers instead.  On systems with 32-bit pointers,
          this option is always disabled.  If the configure script
          determines that your BLAS library uses 32-bit integers, then
          operations using the following libraries are limited to arrays
          with dimensions that are smaller than 2^{31} elements:

             * BLAS

             * LAPACK

             * QRUPDATE

             * SuiteSparse

             * ARPACK

          Additionally, the following libraries use 'int' internally, so
          maximum problem sizes are always limited:

             * GLPK

             * Qhull

          *Note Compiling Octave with 64-bit Indexing::, for more
          details about building Octave with more complete support for
          large arrays.

     '--enable-address-sanitizer-flags'
          Enable compiler options '-fsanitize=address' and
          '-fomit-frame-pointer' for memory access checking.  This
          option is primarily used for debugging Octave.  Building
          Octave with this option has a negative impact on performance
          and is not recommended for general use.  It may also interfere
          with proper functioning of the GUI.

     '--disable-docs'
          Disable building all forms of the documentation (Info, PDF,
          HTML). The default is to build documentation, but your system
          will need functioning Texinfo and TeX installs for this to
          succeed.

     '--enable-float-truncate'
          This option allows for truncation of intermediate floating
          point results in calculations.  It is only necessary for
          certain platforms.

     '--enable-readline'
          Use the readline library to provide for editing of the command
          line in terminal environments.  This option is on by default.

     '--enable-shared'
          Create shared libraries (this is the default).  If you are
          planning to use the dynamic loading features, you will
          probably want to use this option.  It will make your '.oct'
          files much smaller and on some systems it may be necessary to
          build shared libraries in order to use dynamically linked
          functions.

          You may also want to build a shared version of 'libstdc++', if
          your system doesn't already have one.

     '--with-blas=<lib>'
          By default, configure looks for the best BLAS matrix libraries
          on your system, including optimized implementations such as
          the free ATLAS 3.0, as well as vendor-tuned libraries.  (The
          use of an optimized BLAS will generally result in
          several-times faster matrix operations.)  Use this option to
          specify a particular BLAS library that Octave should use.

     '--with-lapack=<lib>'
          By default, configure looks for the best LAPACK matrix
          libraries on your system, including optimized implementations
          such as the free ATLAS 3.0, as well as vendor-tuned libraries.
          (The use of an optimized LAPACK will generally result in
          several-times faster matrix operations.)  Use this option to
          specify a particular LAPACK library that Octave should use.

     '--with-magick=<lib>'
          Select the library to use for image I/O.  The two possible
          values are "GraphicsMagick" (default) or "ImageMagick".

     '--with-sepchar=<char>'
          Use <char> as the path separation character.  This option can
          help when running Octave on non-Unix systems.

     '--without-amd'
          Don't use AMD, disable some sparse matrix functionality.

     '--without-camd'
          Don't use CAMD, disable some sparse matrix functionality.

     '--without-colamd'
          Don't use COLAMD, disable some sparse matrix functionality.

     '--without-ccolamd'
          Don't use CCOLAMD, disable some sparse matrix functionality.

     '--without-cholmod'
          Don't use CHOLMOD, disable some sparse matrix functionality.

     '--without-curl'
          Don't use the cURL library, disable the ftp objects, 'urlread'
          and 'urlwrite' functions.

     '--without-cxsparse'
          Don't use CXSPARSE, disable some sparse matrix functionality.

     '--without-fftw3'
          Use the included FFTPACK library for computing Fast Fourier
          Transforms instead of the FFTW3 library.

     '--without-fftw3f'
          Use the included FFTPACK library for computing Fast Fourier
          Transforms instead of the FFTW3 library when operating on
          single precision (float) values.

     '--without-glpk'
          Don't use the GLPK library for linear programming.

     '--without-hdf5'
          Don't use the HDF5 library, disable reading and writing of
          HDF5 files.

     '--without-opengl'
          Don't use OpenGL, disable native graphics toolkit for
          plotting.  You will need 'gnuplot' installed in order to make
          plots.

     '--without-qhull'
          Don't use Qhull, disable 'delaunay', 'convhull', and related
          functions.

     '--without-qrupdate'
          Don't use QRUPDATE, disable QR and Cholesky update functions.

     '--without-umfpack'
          Don't use UMFPACK, disable some sparse matrix functionality.

     '--without-zlib'
          Don't use the zlib library, disable data file compression and
          support for recent MAT file formats.

     '--without-framework-carbon'
          Don't use framework Carbon headers, libraries, or specific
          source code even if the configure test succeeds (the default
          is to use Carbon framework if available).  This is a platform
          specific configure option for Mac systems.

     '--without-framework-opengl'
          Don't use framework OpenGL headers, libraries, or specific
          source code even if the configure test succeeds.  If this
          option is given then OpenGL headers and libraries in standard
          system locations are tested (the default value is
          '--with-framework-opengl').  This is a platform specific
          configure option for Mac systems.

     See the file 'INSTALL' for more general information about the
     command line options used by configure.  That file also contains
     instructions for compiling in a directory other than the one where
     the source is located.

   * Run make.

     You will need a recent version of GNU Make as Octave relies on
     certain features not generally available in all versions of make.
     Modifying Octave's makefiles to work with other make programs is
     probably not worth your time; instead, we simply recommend
     installing GNU Make.

     There are currently three options for plotting in Octave: the
     external program gnuplot, the internal graphics engine using OpenGL
     coupled with either FLTK or Qt widgets.  Gnuplot is a
     command-driven interactive function plotting program.

     To compile Octave, you will need a recent version of 'g++' or other
     ANSI C++ compiler.  In addition, you will need a Fortran 77
     compiler or 'f2c'.  If you use 'f2c', you will need a script like
     'fort77' that works like a normal Fortran compiler by combining
     'f2c' with your C compiler in a single script.

     If you plan to modify the parser you will also need GNU 'bison' and
     'flex'.  If you modify the documentation, you will need GNU
     Texinfo.

     GNU Make, 'gcc' (and 'libstdc++'), 'gnuplot', 'bison', 'flex', and
     Texinfo are all available from many anonymous ftp archives.  The
     primary site is <ftp://ftp.gnu.org>, but it is often very busy.  A
     list of sites that mirror the software on <ftp://ftp.gnu.org> is
     available by anonymous ftp from
     <ftp://ftp.gnu.org/pub/gnu/GNUinfo/FTP>.

     Octave requires approximately 1.4 GB of disk storage to unpack and
     compile from source (significantly less, 400 MB, if you don't
     compile with debugging symbols).  To compile without debugging
     symbols try the command

          make CFLAGS=-O CXXFLAGS=-O LDFLAGS=

     instead of just 'make'.

   * If you encounter errors while compiling Octave, first see *note
     Installation Problems:: for a list of known problems and if there
     is a workaround or solution for your problem.  If not, see the file
     BUGS for information about how to report bugs.

   * Once you have successfully compiled Octave, run 'make install'.

     This will install a copy of Octave, its libraries, and its
     documentation in the destination directory.  As distributed, Octave
     is installed in the following directories.  In the table below,
     PREFIX defaults to '/usr/local', VERSION stands for the current
     version number of the interpreter, and ARCH is the type of computer
     on which Octave is installed (for example, 'i586-unknown-gnu').

     'PREFIX/bin'
          Octave and other binaries that people will want to run
          directly.

     'PREFIX/lib/octave-VERSION'
          Libraries like liboctave.a and liboctinterp.a.

     'PREFIX/include/octave-VERSION/octave'
          Include files distributed with Octave.

     'PREFIX/share'
          Architecture-independent data files.

     'PREFIX/share/man/man1'
          Unix-style man pages describing Octave.

     'PREFIX/share/info'
          Info files describing Octave.

     'PREFIX/share/octave/VERSION/m'
          Function files distributed with Octave.  This includes the
          Octave version, so that multiple versions of Octave may be
          installed at the same time.

     'PREFIX/libexec/octave/VERSION/exec/ARCH'
          Executables to be run by Octave rather than the user.

     'PREFIX/lib/octave/VERSION/oct/ARCH'
          Object files that will be dynamically loaded.

     'PREFIX/share/octave/VERSION/imagelib'
          Image files that are distributed with Octave.

1.3 Compiling Octave with 64-bit Indexing
=========================================

Note: the following only applies to systems that have 64-bit pointers.
Configuring Octave with '--enable-64' cannot magically make a 32-bit
system have a 64-bit address space.

   On 64-bit systems, Octave uses 64-bit integers for indexing arrays by
default.  If the configure script determines that your BLAS library uses
32-bit integers, then operations using the following libraries are
limited to arrays with dimensions that are smaller than 2^{31} elements:

   * BLAS

   * LAPACK

   * QRUPDATE

   * SuiteSparse

   * ARPACK

   Additionally, the following libraries use 'int' internally, so
maximum problem sizes are always limited:

   * GLPK

   * Qhull

   Except for GLPK and Qhull, these libraries may also be configured to
use 64-bit integers, but most systems do not provide packages built this
way.  If you wish to experiment with large arrays, the following
information may be helpful.

   To determine the integer size of the BLAS library used by Octave, the
following code can be executed:

     clear all;
     N = 2^31;
     ## The following line requires about 8 GB of RAM!
     a = b = ones (N, 1, "single");
     c = a' * b

   If the BLAS library uses 32-bit integers, an error will be thrown:

     error: integer dimension or index out of range for Fortran
     INTEGER type

   Otherwise, if the BLAS library uses 64-bit integers, the result is:

     c = 2^31 = 2147483648

   Note that the test case above usually requires twice the memory, if A
and B are not assigned by 'a = b = ...'.  Note further, that the data
type 'single' has a precision of about 23 binary bits.  In this
particular example no rounding errors occur.

   The following instructions were tested with the development version
of Octave and GCC 4.3.4 on an x86_64 Debian system and may be out of
date now.  Please report any problems or corrections on the Octave bug
tracker.

   The versions listed below are the versions used for testing.  If
newer versions of these packages are available, you should try to use
them, although there may be some differences.

   All libraries and header files will be installed in subdirectories of
'$prefix64' (you must choose the location of this directory).

   * BLAS and LAPACK (<http://www.netlib.org/lapack>)

     Reference versions for both libraries are included in the reference
     LAPACK 3.2.1 distribution from <http://www.netlib.org/>.

        - Copy the file 'make.inc.example' and name it 'make.inc'.  The
          options '-fdefault-integer-8' and '-fPIC' (on 64-bit CPU) have
          to be added to the variable 'OPTS' and 'NOOPT'.

        - Once you have compiled this library make sure that you use it
          for compiling Suite Sparse and Octave.  In the following we
          assume that you installed the LAPACK library as
          $prefix64/lib/liblapack.a.

   * QRUPDATE (<https://sourceforge.net/projects/qrupdate>)

     In the 'Makeconf' file:

        - Add '-fdefault-integer-8' to 'FFLAGS'.

        - Adjust the BLAS and LAPACK variables as needed if your 64-bit
          aware BLAS and LAPACK libraries are in a non-standard
          location.

        - Set 'PREFIX' to the top-level directory of your install tree.

        - Run 'make solib' to make a shared library.

        - Run 'make install' to install the library.

   * SuiteSparse (<http://faculty.cse.tamu.edu/davis/suitesparse.html>)

     Pass the following options to 'make' to enable 64-bit integers for
     BLAS library calls.  On 64-bit Windows systems, use
     '-DLONGBLAS="long long"' instead.

          CFLAGS='-DLONGBLAS=long'
          CXXFLAGS='-DLONGBLAS=long'

     The SuiteSparse makefiles don't generate shared libraries.  On some
     systems, you can generate them by doing something as simple as

          top=$(pwd)
          for f in *.a; do
            mkdir tmp
            cd tmp
            ar vx ../$f
            gcc -shared -o ../${f%%.a}.so *.o
            cd $top
            rm -rf tmp
          done

     Other systems may require a different solution.

   * ARPACK (<https://forge.scilab.org/index.php/p/arpack-ng/>)

        - Add '-fdefault-integer-8' to 'FFLAGS' when running configure.

        - Run 'make' to build the library.

        - Run 'make install' to install the library.

   * ATLAS instead of reference BLAS and LAPACK

     Suggestions on how to compile ATLAS would be most welcome.

   * GLPK

   * Qhull (<http://www.qhull.org>)

     Both GLPK and Qhull use 'int' internally so maximum problem sizes
     may be limited.

   * Octave

     Octave's 64-bit index support is activated with the configure
     option '--enable-64'.

          ./configure \
            LD_LIBRARY_PATH="$prefix64/lib" \
            CPPFLAGS="-I$prefix64/include" LDFLAGS="-L$prefix64/lib" \
            --enable-64

     You must ensure that all Fortran sources except those in the
     'liboctave/external/ranlib' directory are compiled such that
     INTEGERS are 8-bytes wide.  If you are using gfortran, the
     configure script should automatically set the Makefile variable
     'F77_INTEGER_8_FLAG' to '-fdefault-integer-8'.  If you are using
     another compiler, you must set this variable yourself.  You should
     NOT set this flag in 'FFLAGS', otherwise the files in
     'liboctave/external/ranlib' will be miscompiled.

   * Other dependencies

     Probably nothing special needs to be done for the following
     dependencies.  If you discover that something does need to be done,
     please submit a bug report.

        - pcre

        - zlib

        - hdf5

        - fftw3

        - cURL

        - GraphicsMagick++

        - OpenGL

        - freetype

        - fontconfig

        - fltk

1.4 Installation Problems
=========================

This section contains a list of problems (and some apparent problems
that don't really mean anything is wrong) that may show up during
installation of Octave.

   * On some SCO systems, 'info' fails to compile if 'HAVE_TERMIOS_H' is
     defined in 'config.h'.  Simply removing the definition from
     'info/config.h' should allow it to compile.

   * If 'configure' finds 'dlopen', 'dlsym', 'dlclose', and 'dlerror',
     but not the header file 'dlfcn.h', you need to find the source for
     the header file and install it in the directory 'usr/include'.
     This is reportedly a problem with Slackware 3.1.  For Linux/GNU
     systems, the source for 'dlfcn.h' is in the 'ldso' package.

   * Building '.oct' files doesn't work.

     You should probably have a shared version of 'libstdc++'.  A patch
     is needed to build shared versions of version 2.7.2 of 'libstdc++'
     on the HP-PA architecture.  You can find the patch at
     <ftp://ftp.cygnus.com/pub/g++/libg++-2.7.2-hppa-gcc-fix>.

   * On some DEC alpha systems there may be a problem with the 'libdxml'
     library, resulting in floating point errors and/or segmentation
     faults in the linear algebra routines called by Octave.  If you
     encounter such problems, then you should modify the configure
     script so that 'SPECIAL_MATH_LIB' is not set to '-ldxml'.

   * On FreeBSD systems Octave may hang while initializing some internal
     constants.  The fix appears to be to use

          options      GPL_MATH_EMULATE

     rather than

          options      MATH_EMULATE

     in the kernel configuration files (typically found in the directory
     '/sys/i386/conf').  After making this change, you'll need to
     rebuild the kernel, install it, and reboot.

   * If you encounter errors like

          passing `void (*)()' as argument 2 of
            `octave_set_signal_handler(int, void (*)(int))'

     or

          warning: ANSI C++ prohibits conversion from `(int)'
                   to `(...)'

     while compiling 'sighandlers.cc', you may need to edit some files
     in the 'gcc' include subdirectory to add proper prototypes for
     functions there.  For example, Ultrix 4.2 needs proper declarations
     for the 'signal' function and the 'SIG_IGN' macro in the file
     'signal.h'.

     On some systems the 'SIG_IGN' macro is defined to be something like
     this:

          #define  SIG_IGN  (void (*)())1

     when it should really be something like:

          #define  SIG_IGN  (void (*)(int))1

     to match the prototype declaration for the 'signal' function.  This
     change should also be made for the 'SIG_DFL' and 'SIG_ERR' symbols.
     It may be necessary to change the definitions in 'sys/signal.h' as
     well.

     The 'gcc' 'fixincludes' and 'fixproto' scripts should probably fix
     these problems when 'gcc' installs its modified set of header
     files, but I don't think that's been done yet.

     *You should not change the files in '/usr/include'*.  You can find
     the 'gcc' include directory tree by running the command

          gcc -print-libgcc-file-name

     The directory of 'gcc' include files normally begins in the same
     directory that contains the file 'libgcc.a'.

   * Some of the Fortran subroutines may fail to compile with older
     versions of the Sun Fortran compiler.  If you get errors like

          zgemm.f:
                  zgemm:
          warning: unexpected parent of complex expression subtree
          zgemm.f, line 245: warning: unexpected parent of complex
            expression subtree
          warning: unexpected parent of complex expression subtree
          zgemm.f, line 304: warning: unexpected parent of complex
            expression subtree
          warning: unexpected parent of complex expression subtree
          zgemm.f, line 327: warning: unexpected parent of complex
            expression subtree
          pcc_binval: missing IR_CONV in complex op
          make[2]: *** [zgemm.o] Error 1

     when compiling the Fortran subroutines in the 'liboctave/external'
     subdirectory, you should either upgrade your compiler or try
     compiling with optimization turned off.

   * On NeXT systems, if you get errors like this:

          /usr/tmp/cc007458.s:unknown:Undefined local
                symbol LBB7656
          /usr/tmp/cc007458.s:unknown:Undefined local
                symbol LBE7656

     when compiling 'Array.cc' and 'Matrix.cc', try recompiling these
     files without '-g'.

   * Some people have reported that calls to system() and the pager do
     not work on SunOS systems.  This is apparently due to having
     'G_HAVE_SYS_WAIT' defined to be 0 instead of 1 when compiling
     'libg++'.

   * On systems where the reference BLAS library is used the following
     matrix-by-vector multiplication incorrectly handles NaN values of
     the form 'NaN * 0'.

          [NaN, 1; 0, 0] * [0; 1]
          =>
          [ 1
            0 ]

          correct result =>
          [ NaN
            0   ]

     Install a different BLAS library such as OpenBLAS or ATLAS to
     correct this issue.

   * On NeXT systems, linking to 'libsys_s.a' may fail to resolve the
     following functions

          _tcgetattr
          _tcsetattr
          _tcflow

     which are part of 'libposix.a'.  Unfortunately, linking Octave with
     '-posix' results in the following undefined symbols.

          .destructors_used
          .constructors_used
          _objc_msgSend
          _NXGetDefaultValue
          _NXRegisterDefaults
          .objc_class_name_NXStringTable
          .objc_class_name_NXBundle

     One kluge around this problem is to extract 'termios.o' from
     'libposix.a', put it in Octave's 'src' directory, and add it to the
     list of files to link together in the makefile.  Suggestions for
     better ways to solve this problem are welcome!

   * If Octave crashes immediately with a floating point exception, it
     is likely that it is failing to initialize the IEEE floating point
     values for infinity and NaN.

     If your system actually does support IEEE arithmetic, you should be
     able to fix this problem by modifying the function
     'octave_ieee_init' in the file 'lo-ieee.cc' to correctly initialize
     Octave's internal infinity and NaN variables.

     If your system does not support IEEE arithmetic but Octave's
     configure script incorrectly determined that it does, you can work
     around the problem by editing the file 'config.h' to not define
     'HAVE_ISINF', 'HAVE_FINITE', and 'HAVE_ISNAN'.

     In any case, please report this as a bug since it might be possible
     to modify Octave's configuration script to automatically determine
     the proper thing to do.

   * If Octave is unable to find a header file because it is installed
     in a location that is not normally searched by the compiler, you
     can add the directory to the include search path by specifying (for
     example) 'CPPFLAGS=-I/some/nonstandard/directory' as an argument to
     'configure'.  Other variables that can be specified this way are
     'CFLAGS', 'CXXFLAGS', 'FFLAGS', and 'LDFLAGS'.  Passing them as
     options to the configure script also records them in the
     'config.status' file.  By default, 'CPPFLAGS' and 'LDFLAGS' are
     empty, 'CFLAGS' and 'CXXFLAGS' are set to "-g -O2" and 'FFLAGS' is
     set to "-O".

