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\title{The Toplevel \File{configure.ac} Pamphlet}
\author{Gabriel Dos~Reis}

\begin{document}
\maketitle

\begin{abstract}
  This pamphlet details the configuration process of setting up 
  \Tool{OpenAxiom} for build from source codes. 
  It also explains general dependencies on external tools.  
  The configuration process scrutinizes the build, host,  and target
  environments, and finally instantiates \File{Makefile}s for building
  \Tool{OpenAxiom} interpreter, compiler, libraries, and auxiliary tools
  where appropriate.
\end{abstract}

\section{Introduction}
\label{sec:intro}

This is the top-level \Tool{Autoconf} description that sets up the
minimum environment for building \Tool{OpenAxiom}.  This effort
strives for describing the build machinery at a sufficiently abstract
level that
enables interoperability with existing conventional frameworks, \eg{}
the GNU build framework.
The task is compounded by the fact that the existing \Tool{OpenAxiom} system 
is complex and very poorly documented, with blatantly conflicting or
questionable codes. 

The \Tool{OpenAxiom} system is written for the most part in Lisp, or 
thereof.  That in itself is a great source of portability 
problems\footnote{even after half a century of existence}, 
let alone issues related to insulation from mainstream
development tools, dependence on particular Lisp implementation details, etc.
A tiny part of it, mainly the interface with host operating system, is
written in the C programming language.  That does not improve on the 
portability problems.  Fortunately, there are well-supported, 
widely used, widely available, well tested tools supporting
C-derived development environments across platforms.  The GNU 
\Tool{Autotools} being one of them.  For the moment, we only make use of
the \Tool{Autoconf} component.  This build machinery does not 
use \Tool{Automake} and \Tool{Libtool}.  People intending to modify
this part of the build machinery are expected to be familiar with 
\Tool{Autotconf}.

The \File{Makefile} pamphlets that compose the build machinery are
written in a way that abstracts platform idiosyncracies into
parameters.  The purpose of the \File{configure.ac} script is to
find values for those parameters, on a given platform, necessary to
instantiate the \File{Makefile}s, and therefore to set up a concrete
build machinery.  And that task must be accomplished portably.

\section{Generalities on build instantiations}

\subsection{Two actors}

The instantiation of the abstract build machinery description requires
that we gather information from two platforms:
\begin{enumerate}
\item the \emph{build platform}, and 
\item the \emph{host platform}.
\end{enumerate}

The build platform is where we build the system, \eg{} where
the \File{configure} script is executed.  The host platform
is where \Tool{OpenAxiom} will run.  Note that in full generality, there is 
a third platform: the \emph{target platform}.  It is the plaform for which
we are building the system.

For typical build instantiations, those  three  platforms are the same: we 
call that a \emph{native build instantiation} or just \emph{native build}.
The OpenAxiom system only support native build at the moment, due to its
dependence on \Tool{GCL} which supports only native build.

To facilitate the porting of programs across platforms, the GNU build
system has standardized on designation of platforms, called
\emph{configuration names}.  A configuration name used to be
made of three parts\footnote{hence the term \emph{canonical triplet} in 
    earlier versions of \Tool{Autoconf}}:
\textsl{cpu--vendor--os}.  Examples are
[[i686-pc-linux-gnu]], or [[sparc-sun-solaris2.8]].

The \textsl{cpu}
part usually designates the type of processor used on the platform.
Examples are [[i686]], or [[sparc]], or [[x86_64]].

The \textsl{vendor} part formally designates the manufacturer of
the platform.  In many cases it is simply [[unknown]].  However,
in specific cases, you can see the name of a workstation vendor such
as [[sun]], or [[pc]] for an IBM PC compatible system.

The \textsl{os} part can be either \textsl{system} (such as [[solaris2.8]])
or \textsl{kernel--system} (such as [[linux-gnu]]).

Here is how we get the canonical names for the above three platforms:
<<host build target platfoms>>=
AC_CANONICAL_SYSTEM

open_axiom_installdir=$libdir/open-axiom/$target/$PACKAGE_VERSION
AC_SUBST(open_axiom_installdir)

@
After that call, the configuration names of the three platforms
are available in the shell variables [[build]], [[host]], and [[target]].

\subsubsection{Cross build}

As we said earlier, a native build instantiation is one where all 
[[build]], [[host]], and [[target]] have the same value.  However,
when porting programs to other platforms, it is not always possible
to do a native build --- either because all the tools are not
available on that machine, or because it is much more convenient to
build the software on a faster machine. Both situations are quite
common.

Those considerations bring us to the notion of cross build 
instantiation (also called cross compilation).  
We say that the build instantiation is a \emph{cross build} when
the build platform is different from the target platform; \eg{}, when
[[build]] $\neq$ [[target]].  

For the moment, the \Tool{OpenAxiom} base source code is written
in a way that does not support cross build.  However, we do
want to make cross build possible; consequently we issue
a warning when we detect attempt at cross build:
<<host build target platfoms>>=
if test $build != $target; then
   AC_MSG_WARN([Cross build is not supported.])
   AC_MSG_WARN([Please notify open-axiom-devel@open-axiom.org if you succeed.])
fi
@
Note that we do not stop the configuration process because we do seek
contributions for cross build support.

Note that the shell variable [[cross_compiling]],
set by the \Tool{Autoconf} macro [[AC_PROG_CC]], indicates whether
the C compiler used is a cross compiler.

\subsubsection{Canadian cross}

As we said previously, most software don't care about the target 
platform.  But compilers do.  And \Tool{OpenAxiom} does because, among
other things, it uses Lisp and C compilers, and it provides a Spad compiler.
Another type of build instantiation arises when the host platform
is different from the target platform.  The resulting compiler
is called a \emph{cross compiler}.  Please note the distinction here:
a compiler that is cross compiled with [[host]] $=$ [[target]] is 
not a cross compiler; it is a \emph{native compiler}. 
A cross compiler is one with [[host]] $\neq$ [[target]].  

The type of the compiler should not be confused with the type of the 
build instantiation.  It perfectly makes sense to have a build
instantiation that cross builds a cross-compiler, \ie{} all three
platforms are different: This is called \emph{Canadian cross}.
The \Tool{OpenAxiom} system does not that support that level of
sophistication yet.  Although we could test for Canadian cross build
at this point, we delay that check for when we look for a C compiler.

\subsection{Directories for the build instantiation}

Although \Tool{OpenAxiom} does not support cross build yet, let
alone Canadian cross, we want to make sure that we do not write
the build machinery in a way that actively unsupports 
cross build.  Consequently, in the build tree, we sequester
tools that we build and use on the build platform,
in  sub-directories different from others.
<<host build target platfoms>>=
## Where tools for the build platform are sequestered
axiom_build_sharedir=$axiom_builddir/share
@

\section{Host characteristics}

As mentioned in the introduction, a small part of \Tool{OpenAxiom} is
written in the C programming language.  That C runtime support
can be decomposed in three components:
\begin{enumerate}
\item core runtime support,
\item graphics (including HyperDoc), and
\item terminal I/O.
\end{enumerate}

\subsection{Core runtime}

\subsubsection{Signals}

The host platform must be able to handle signals.  Although, this is 
not strictly necessary, that is the way \Tool{OpenAxiom} source code
is currently written.  We ask for a POSIX or ISO C semantics, though
we have a strong preference for POSIX-conformant semantics.

<<C headers and libraries>>=
AC_CHECK_HEADERS([stdint.h inttypes.h])
AC_TYPE_UINT8_T
AC_CHECK_HEADERS([signal.h],
                 [],
                 [AC_MSG_ERROR([OpenAxiom needs signal support.])])
AC_CHECK_DECLS([sigaction], [], [], 
               [#include <signal.h>])
@


\subsubsection{Files and directtories}

Some parts of \Tool{OpenAxiom} manipulate files and directories.  They
more or less directly reflect the underlying platform semantics.
For the moment, we require POSIX semantics, though that does not
seem necessary.  That restriction should be removed as soon as possible.

<<C headers and libraries>>=
AC_CHECK_HEADERS([sys/stat.h],
                 [],
		 [AC_MSG_ERROR([OpenAxiom needs <sys/stat.h>])])
case $host in
    *mingw*)
        ;;
    *)
	AC_CHECK_HEADERS([dirent.h],
			 [],
			 [AC_MSG_ERROR([OpenAxiom needs <dirent.h>])])
        ;;
esac

AC_CHECK_HEADERS([unistd.h], [],
                 [AC_MSG_ERROR([OpenAxiom needs <unistd.h>])])
AC_CHECK_DECLS([getuid, geteuid, getgid, getegid], [], [],
               [#include <unistd.h>])

AC_CHECK_DECLS([kill], [], [],
               [#include <signal.h>])
@

\subsubsection{Sockets}

The host environment must be capable of handling communication through
sockets.  This is required for interfacing \Tool{AXIOMsys}
and \Tool{Superman}.  Notice that ideally, we should decouple
that interface in such a way that we can still build \Tool{OpenAxiom}
when \Tool{Superman} is not needed or a socket library is not
available.

<<C headers and libraries>>=
case $host in
    *mingw*)
	AC_CHECK_HEADERS([winsock2.h],
	                [axiom_host_has_socket=yes],
			[])
	axiom_c_runtime_extra="-lwsock32"
	;;
    *)
        AC_CHECK_HEADERS([sys/socket.h], 
                         [axiom_host_has_socket=yes],
		         [])
	;;
esac
if test x$axiom_host_has_socket != xyes; then \
    AC_MSG_ERROR([OpenAxiom needs suport for sockets.])
fi
## solaris-based systems tend to hide the socket library.
case $host in
    *solaris*)
       AC_SEARCH_LIBS([accept], [socket],
	   [], [AC_MSG_ERROR([socket library not found])])
       AC_SEARCH_LIBS([gethostbyname], [nsl])
       ;;
    *) ;;
esac

AC_SUBST(axiom_c_runtime_extra)

AC_EGREP_CPP([has_af_local],
             [#if HAVE_SYS_SOCKET_H
#  include <sys/socket.h>
#else
#  include <winsock2.h>
#endif
#ifdef AF_LOCAL
   has_af_local
#endif
             ],
             [AC_DEFINE([HAVE_AF_LOCAL], [1], [Host has AF_LOCAL])])


AC_EGREP_CPP([has_af_unix],
             [#if HAVE_SYS_SOCKET_H
#  include <sys/socket.h>
#else
#  include <winsock2.h>
#endif
#ifdef AF_UNIX
   has_af_unix
#endif
             ],
             [AC_DEFINE([HAVE_AF_UNIX], [1], [Host has AF_UNIX])])

@


\subsection{Terminal I/O}

<<C headers and libraries>>=
AC_CHECK_HEADERS([sys/wait.h])

if test x"$ac_cv_header_sys_wait_h" = xyes; then \
    AC_CHECK_DECLS([wait], 
                   [], 
                   [], 
                   [#include <sys/wait.h>])
fi

AC_CHECK_DECLS([fork],
               [],
               [],
               [#include <unistd.h>])

## Does this system have openpty or shall we emulate?
AC_CHECK_HEADERS([sys/ioctl.h pty.h util.h libutil.h termios.h])
AC_CHECK_DECLS([openpty],[],[],
   [#if HAVE_PTY_H
#  include <pty.h>
#endif
#if HAVE_UTIL_H
#  include <util.h>
#endif
#if HAVE_SYS_IOCTL_H
#  include <sys/ioctl.h>
#endif
#if HAVE_TERMIOS_H
#  include <termios.h>
#endif
#if HAVE_LIBUTIL_H
#  include <sys/types.h>
#  include <libutil.h>
#endif
   ])
if test x"$ac_cv_have_decl_openpty" = xyes; then \
   AC_SEARCH_LIBS([openpty],[util])
fi

axiom_use_sman=1
if test x"$ac_cv_have_decl_fork" = xyes \
     -a x"$ac_cv_have_decl_wait" = xyes; then \
    axiom_c_runtime="$axiom_c_runtime terminal_io"
    axiom_src_all="$axiom_src_all all-sman all-clef"
    axiom_src_subdirs="$axiom_src_subdirs clef sman"
    AXIOM_MAKEFILE([src/clef/Makefile])
    AXIOM_MAKEFILE([src/sman/Makefile])
else
    axiom_use_sman=0
    AC_MSG_NOTICE([Superman component is disabled.])
fi

AC_DEFINE_UNQUOTED([OPENAXIOM_USE_SMAN], [$axiom_use_sman],
                   [Whether to use the session manager as driver.])

axiom_src_all="all-input $axiom_src_all"

@


\subsection{Graphics}

\subsubsection{Where is X11?}

One of the thorniest issues with programs that use the X Window System
is portability.  There exist many implementations of the X11
specification, each with its own variations, extensions, and what
not.  Designing hand-written makefiles for such programs can be a
daunting task, fraut with all kinds of traps.  Fortunately, \Tool{Autoconf}
provides us with some help, namely the macro [[AC_PATH_X]] and 
[[AC_PATH_XTRA]].  The former searches the directories where the
X11 include files and the library files reside.  The latter is an
enhanced version that
\begin{itemize}
\item computes the C compiler flags required by X11;
\item computes the linker flags required by X11;
\item checks for special libraries that some systems need in order to
   compile X11 programs;
\item checks for special X11R6 libraries that need to be linked before
  the flag [[-lX11]].
\end{itemize}

<<C headers and libraries>>=
AC_PATH_XTRA
## Output directives for the C compiler
AC_SUBST(X_CLFAGS)
## Output directives for the linker
AC_SUBST(X_LIBS)
## Output any extra libraries required by X11
AC_SUBST(X_EXTRA_LIBS)

## Finally, output the list of libraries that need to appear before -lX11
## Some part of OpenAxiom depends on Xpm.  That library has kind uncertain
## future.  At some point in the past, it was deprecated, to be
## replaced by xpm-nox; then came back again.  So, its support may
## vary from system to system.  For the moment, we assume that if X11
## is found then, Xpm is already present.  Though, clearly that is a
## very optimistic assumption.  Long term, OpenAxiom should get rid of
## dependence on Xpm.  A nearly fool-proof test would be probably
## inspired by AC_PATH_XTRA.  I don't have time to get to that 
## complication right now.  Will fix later.
X_PRE_LIBS="-lXpm $X_PRE_LIBS"
AC_SUBST(X_PRE_LIBS)

## If the system supports X11, then build graphics

# Check for Qt utilities.
AC_CHECK_PROGS([OA_QT_MOC], [moc])
AC_CHECK_PROGS([OA_QT_QMAKE], [qmake])
if test -n "$OA_QT_MOC"; then
  AC_MSG_CHECKING([Qt version])
  oa_qt_version=`"$OA_QT_MOC" -v 2>&1 | sed -e 's/^.*(\(.*\))$/\1/'`
  AC_MSG_RESULT([$oa_qt_version])
  case $oa_qt_version in
    *[1-3]\.[0-9]+\.[0-9]+)
       AC_MSG_WARN([This version of Qt is too old for OpenAxiom.])
       ;;
  esac
fi

axiom_use_x=no
if test -z $no_x; then
    axiom_use_x=yes
    axiom_c_runtime="$axiom_c_runtime graphics"
    axiom_src_all="$axiom_src_all all-graph"
    axiom_src_subdirs="$axiom_src_subdirs graph"
    AXIOM_MAKEFILE([src/graph/Makefile])
    AXIOM_MAKEFILE([src/graph/Gdraws/Makefile])
    AXIOM_MAKEFILE([src/graph/view2D/Makefile])
    AXIOM_MAKEFILE([src/graph/view3D/Makefile])
    AXIOM_MAKEFILE([src/graph/viewAlone/Makefile])
    AXIOM_MAKEFILE([src/graph/viewman/Makefile])
else
    AC_MSG_NOTICE([The Garphics component is disabled.])
fi
AC_SUBST(axiom_src_all)
AC_SUBST(axiom_use_x)
@

\subsubsection{HyperDoc}

The HyperDoc component needs string pattern matching.  
We require [[<regex.h>]], with POSIX-conformant definition.  We used
to key build of HyperDoc component on the availability of X11
functionalities.  That, however, is a severe restriction.  Not all
of the HyperDoc components need X11.  Some, such as [[htadd]], don't
need X11 at all.  Therefore we have lifted part of the restrictions.
See \File{src/hyper/Makefile} for more details.  Note that is we don't
build the HyperDoc component, the compilation of algebra files are
drawn in [[Unexpected HT command]] noise.
<<C headers and libraries>>=
openaxiom_host_has_regex=
AC_CHECK_HEADER([regex.h], 
		[openaxiom_host_has_regex=yes],
		[openaxiom_host_has_regex=no])
AC_SUBST(openaxiom_host_has_regex)
@


\subsection{Lisp runtime}

\subsubsection{Runtime checking}

\Tool{OpenAxiom}'s Lisp runtime platform may be instructed to perform
runtime checks.  This may be useful when chasing Heinsenbugs.
It probably should be the default mode on development or experimental
branches.
<<runtime checking>>=
axiom_optimize_options=speed
## Shall we proclaim safety?
axiom_enable_checking=no          # don't turn on checking by default.
AC_ARG_ENABLE([checking], [  --enable-checking  turn runtime checking on],
              [case $enableval in
                  yes|no) axiom_enable_checking=$enableval ;;
                  *) AC_MSG_ERROR([erroneous value for --enable-checking]) ;;
               esac])
if test x"$axiom_enable_checking" = xyes; then
   case $axiom_lisp_flavor in
     gcl) # GCL-2.6.x does not understand debug.
        axiom_optimize_options="$axiom_optimize_options safety" 
        ;;
     *) axiom_optimize_options="$axiom_optimize_options safety debug" 
        ;;
   esac
   AC_MSG_NOTICE([runtime checking may increase compilation time])
fi

AC_SUBST(axiom_enable_checking)
AC_SUBST(axiom_optimize_options)

## Parse args for profiling-enabled build.
oa_enable_profiling=no
AC_ARG_ENABLE([profiling], [  --enable-profiling  turn profiling on],
              [case $enableval in
                  yes|no) oa_enable_profiling=$enableval ;;
                  *) AC_MSG_ERROR([erroneous value for --enable-profiling]) ;;
               esac])

AC_SUBST(oa_enable_profiling)
@


\Tool{GCL} relies on the libirary \Tool{BFD}, the include 
headers of which may not exist (quite common).  In order to avoid 
\Tool{GCL} build failure, we test for the existence of [[<bfd.h>]]
and the corresponding library.  We configure \Tool{GCL} to
use its own copy of \Tool{BFD} accordingly.   FIXME: This must
be taken care of by \Tool{GCL} itself.
<<gcl options>>=
axiom_host_has_libbfd=
## Check for these only if we are going to build GCL from source.
case $axiom_all_prerequisites in
    *all-gcl*)
	AC_CHECK_HEADER([bfd.h])
	AC_HAVE_LIBRARY([bfd], [axiom_host_has_libbfd=yes])

	axiom_gcl_bfd_option=
	if test x"$ac_cv_header_bfd_h" = xyes \
	    && test x"$axiom_host_has_libbfd" = xyes; then
	    axiom_gcl_bfd_option="--disable-dynsysbfd"
	else
	    axiom_gcl_bfd_option="--disable-statsysbfd --enable-locbfd"
	fi
        ;;
    *)    
        # Nothing to worry about
        ;;
esac
@

\Tool{GCL} has an elaborate memory management system and 
\Tool{OpenAxiom} seems to 
put ``unusual'' pressure on it.  Here we specify some values that have
been empirically known to work.
<<gcl options>>=
# axiom_gcl_mm_option="--enable-maxpage=256*1024"
@

Furthermore, we don't need (at the moment) \Tool{GCL} to build support for
X Window system or TCL/TK:
<<gcl options>>=
axiom_gcl_x_option="--disable-tkconfig --disable-x --disable-xgcl"
@

Under some unusual circumstances, \Tool{GLC}'s \Tool{configure} will
fail to properly detect usable \Tool{Emacs} directories, and the
build will mysteriously fail later.  We temporarily work
around that bug as follows:
<<gcl options>>=
axiom_gcl_emacs="--enable-emacs=correct"
@


Other aspects depend on the platform being considered.


\Tool{OpenAxiom} source code had developed the appalling and irritating habit
of testing for
platforms, when in fact it is interested in functionalities.
The outcome is an ever-growing pile of increasing disgusting hacks.
For example, most the XXXplatform below really have nothing to
do with platforms.  

<<platform specific bits>>=
<<gcl options>>

case $GCC in
  yes)
     CCF="-O2 -Wall -D_GNU_SOURCE"
     ;;
esac

case $target in
    *bsd*|*dragonfly*)
	CCF="-O2 -Wall"
	;;
    windows)
	SRCDIRS=bootdir interpdir sharedir algebradir etcdir docdir inputdir
	;;
    *solaris*)
        AC_DEFINE([SUNplatform], [], [SunOS flavour])
	;;
    powerpc*darwin*)
	CCF="-O2 -Wall -D_GNU_SOURCE \
	    -I/usr/include -I/usr/include/sys"
        axiom_gcl_bfd_option="--disable-statsysbfd \
                                --enable-machine=powerpc-macosx"
        axiom_gcl_mm_option="--enable-vssize=65536*2"
	;;
esac

GCLOPTS="$axiom_gcl_emacs $axiom_gcl_bfd_option $axiom_gcl_mm_option $axiom_gcl_x_option"

AC_SUBST(CCF)
AC_SUBST(GCLOPTS)
@

The C preprocessor symbols [[BSDplatform]], [[LINUXplatform]], etc. are being
used as ``catch all'' for unstructured codes.  They should be
removed from the source base.  Any source file using those should be 
properly documented as its needs are, and a narrowed, specific configure
test should be added.


\section{The build platform}

\subsection{Build utilities}
Most of the tools we're testing for are with respect to the build
environment.  However, notice that since we only support \emph{native}
build at the moment, the tests are also for the host and target
platforms.
<<build utils>>=
## Accumulate list of utils needed for the build platform
## It is vital that noweb is present in the build environement.
axiom_all_prerequisites=

<<find make>>

<<file utils>>

<<awk and tar program>>

<<binary utils>>

<<doc utils>>

<<find lisp>>
<<lisp options>>
<<compiled lisp extension>>

## Does it make sense to pretend that we support multithreading?
oa_enable_threads=no
AC_ARG_ENABLE([threads], [  --enable-threads   turn on threads support],
              [case $enableval in
                  yes|no) oa_enable_threads=$enableval ;;
                  *) AC_MSG_ERROR([erroneous value for --enable-threads]) ;;
               esac])

# GNU compiler wants to have a hint about multithreading.
case $GCC,$oa_enable_threads in
   yes,yes)
     axiom_cflags="$axiom_cflags -pthread"
esac

AC_SUBST(oa_enable_threads)

AC_SUBST(axiom_all_prerequisites)
@

The next paragraphs detail each of the cluster of build utilities
[[configure]] looks for.

\paragraph{The \Tool{Make} program.}

Of course, no build can proceed with \File{Tool} inexisting from
the build-environment.  We insist on GNU \Tool{Make} program as there 
are way too many variations, way too many incompatible implementations 
and extensions.  Please, note that this requirement just reflects
\Tool{OpenAxiom}'s dependencies on external toos:  \Tool{OpenAxiom} relies on 
\Tool{GCL}, which in turn uses \Tool{GCC}.  Building \Tool{GCC} requires
\Tool{GNU Make}, and \Tool{GCL} itself requires \Tool{GNU Make}.
<<find make>>=
case $build in
    *linux*)
	# GNU/Linux systems come equipped with GNU Make, called `make'
        AC_CHECK_PROGS([MAKE], [make],
                       [AC_MSG_ERROR([Make utility missing.])])
	;;
    *)
        # Other systems tend to spell it `gmake' and such
        AC_CHECK_PROGS([MAKE], [gmake make],
                       [AC_MSG_ERROR([Make utility missing.])])
	if ! $MAKE --version | grep 'GNU' 2>/dev/null; then
	    AC_MSG_ERROR([OpenAxiom build system needs GNU Make.])
	fi
	;;
esac

@

\paragraph{C compiler}
First of all, check for a C compiler.  As written, this test is OK 
because currently we support only native builds.  However,
 it needs to be more carefully written when we move to cross-compilation.
<<find C compiler>>=
AC_PROG_CC
AC_PROG_CXX

## What is the extension of object and executable files on this platform?
AC_OBJEXT
AC_DEFINE_UNQUOTED([OPENAXIOM_EXEEXT], ["$ac_cv_exeext"], 
                   [Extension of executable file.])

## Byte order of the host.
AC_C_BIGENDIAN

@

\paragraph{File utils}
Then, check for a usable [[install]] program.  Also, find out
way to hard- or soft-link files.  

After a recent migration to
\Tool{Autoconf-2.60}, it turns out that all possibilities of
soft-linking are tried (to ``play safe''), and if any variation
fails then, [[LN_S]] is defined to [[cp -p]], which works
only for files as sources.  But, the only way we currently
use [[LN_S]] is when the first argument is a directory.  So, the 
``portability help'' we get from \Tool{Autoconf} is no help.  
Consequently, the test for
[[ln -s]] is commented out for the moment.
<<file utils>>=
AC_PROG_INSTALL
# AC_PROG_LN_S
AC_CHECK_PROG([TOUCH], [touch],
              [touch], [AC_MSG_ERROR(['touch' program is missing.])])
AC_CHECK_PROGS([MKTEMP], [mktemp])
@

\paragraph{The [[awk]] program}
The old build machinery needs \Tool{awk} on the build machine for
extracting algebra definitions.  The same tool is needed on the
host machine for proper run of HyperDoc utilities.  Note that at
the moment we do not make a distinction between the build machine
and the host machine (though that may change in the future).

<<awk and tar program>>=
AC_PROG_AWK
AC_PATH_PROGS([HOST_AWK],[awk nawk gawk mawk])

@

\paragraph{Binary utils.}

We need to know how to put object files into archives.
<<binary utils>>=
AC_CHECK_PROG([AR], [ar], [ar], [AC_MSG_ERROR([program 'ar' is missing])])
@

\paragraph{Doc utils.}

OpenAxiom sources is literate, and it uses the \Tool{noweb} technology.
\Tool{noweb} is used to extract both the actual source code from the
pamphlet files, and the documentation as \LaTeX{} source files.
There are many platforms on which \Tool{noweb} is not installed
by default.  There is tarball of the dependencies on OpenAxiom's
web site to people to grab in case they don't have \Tool{noweb}
or \Tool{GCL}.  What we do is that if noweb is not found, then
we try to build one from the tarball of dependency.  For that
to work, the protocol is that the user has placed \Tool{noweb}'s source
files in a directory named \File{noweb/} at the top level.  Normally, 
this works right when one follows the installation instructions.
%
<<doc utils>>=
AC_PATH_PROG([PDFLATEX], [pdflatex])
if test -z "$PDFLATEX"; then
   AC_PATH_PROG([LATEX], [latex],
                [AC_MSG_NOTICE([Documentation is disabled.])])
fi

AC_CHECK_PROGS([MAKEINDEX], [makeindex])

## ---------------------------------------
## Make sure noweb executable is available
## ---------------------------------------
AC_CHECK_PROGS([NOTANGLE], [notangle])
AC_CHECK_PROGS([NOWEAVE], [noweave])

## In case noweb is missing we need to build our own.
if test -z $NOTANGLE -o -z $NOWEAVE ; then
    ## Yes, but do we have the source files to build from?
    if test ! -d ${srcdir}/noweb; then
       AC_MSG_NOTICE([OpenAxiom requires noweb utilties])
       AC_MSG_ERROR([Please get the tarball of dependencies and reconfigure])
    fi
    NOTANGLE='$(axiom_build_bindir)/notangle'
    NOWEAVE='$(axiom_build_bindir)/noweave'
    axiom_all_prerequisites="$axiom_all_prerequisites all-noweb"
fi
@

\paragraph{The Lisp platform.}

\Tool{OpenAxiom} uses Lisp as its main platform.  If no Lisp implementation
is available in the build environment (or if \Tool{OpenAxiom} is told not
to look for one) then \Tool{OpenAxiom} must build its own version from the
copy of \Tool{GCL} sources it keeps in the \File{gcl/} directory.
<<find lisp>>=
## ------------------------
## -- Which Lisp to use? --
## ------------------------
##
## We will default to GCL later, if no lisp implementation is specified.
axiom_lisp=
axiom_lisp_flavor=unknown
# Most Lisp systems don't use conventional methods for building programs.
oa_standard_linking=no
AC_ARG_WITH([lisp], [ --with-lisp=L         use L as Lisp platform],
              [axiom_lisp=$withval])
@

The [[configure]] option \verb!--with-lisp=L! specifies which
Lisp implementation flavor to use for building OpenAxiom.  For all values
of [[L]], except \Tool{GCL}, the assumption is that the Lisp
image [[L]] is available in the build environment.  For \Tool{GCL}, 
we make an exception: if no GCL image is available, or if
the option \verb!--enable-gcl! is specified then \Tool{OpenAxiom}
builds its own version from the source tree.
<<find lisp>>=
## If --enable-gcl is specified, we need to check for coonsistency
axiom_include_gcl=
if test -z $axiom_lisp; then
    AC_ARG_ENABLE([gcl], [  --enable-gcl   build GCL from OpenAxiom source],
                  [case $enableval in
                       yes|no) axiom_include_gcl=$enableval ;;
                       *) AC_MSG_ERROR([erroneous value for --enable-gcl]) ;;
                   esac])
fi
@

Do we need to build our own version of \Tool{GCL}?  The answer is yes, if
\begin{itemize}
\item the option \verb!--with-lisp! is not specified, and
   no Lisp image is available in the build environment; or
\item we found a \Tool{GCL} image, but it is too old for OpenAxiom.
\end{itemize}
Consequently, we need to check for \Tool{GCL} and its version:
<<find lisp>>=
## We need to build our own GCL if none is avalaible.
if test -z $axiom_lisp; then
    AC_CHECK_PROGS([AXIOM_LISP], [sbcl gcl ecl clisp ccl ccl64])
    ## A lisp may not be available AND the GCL source may also
    ## be missing.  Instruct user to either build one or get
    ## the dependencies from our website.
    if test -z $AXIOM_LISP && test ! -d ${srcdir}/gcl; then
       AC_MSG_ERROR([OpenAxiom requires a Lisp system.  Either separately build one (GCL-2.6.7, GCL-2.6.8, SBCL, CLisp), or get the dependency tarball from OpenAxiom download website.])
    fi
    axiom_lisp=$AXIOM_LISP
else
    ## Honor use of Lisp image specified on command line
    AXIOM_LISP=$axiom_lisp
    AC_SUBST(AXIOM_LISP)
    :
fi

## Some Lisp systems are just too buggy to use.
case $AXIOM_LISP in
   *gcl*)
      AC_MSG_CHECKING([$AXIOM_LISP version])
      v=`$AXIOM_LISP -batch -eval "(format t \"~S\" (lisp-implementation-version))"`
      AC_MSG_RESULT([$v])
      case $v in
	*2.6.7*|*2.6.8*) ;;         # OK
	*)
	  AC_MSG_WARN([$v is not supported by this version of OpenAxiom.  $AXIOM_LISP will be ignored.])
	  AXIOM_LISP=
	  ;;
      esac
      ;;
   # SBCL-1.0.29 has a nasty regression that prevents OpenAxiom build
   *sbcl*)
      AC_MSG_CHECKING([$AXIOM_LISP version])
      v=`$AXIOM_LISP --version`
      AC_MSG_RESULT([$v])
      case $v in
	*1.0.29)
	   AC_MSG_ERROR([This version of SBCL has a bug that breaks OpenAxiom build.  Consider SBCL-1.0.30 or higher.])
	   ;;
      esac
      ;;
esac

@

We may be presented with incoherent options if
\begin{itemize}
\item \verb!--disable-gcl! is used without specifying a Lisp image, or
\item \verb!--with-lisp! is used but we are also told to build \Tool{GCL}.
\end{itemize}
<<find lisp>>=
## Coherence check for GCL inclusion.
case $axiom_include_gcl,$axiom_lisp in
    ,|no,|yes*)
       ## It doesn't make sense not to include GCL when no Lisp image
       ## is available.  Give up.
       if test $axiom_include_gcl,$AXIOM_LISP = no,; then
	   AC_MSG_ERROR([--disable-gcl specified but no GCL image found])
       fi

       ## No Lisp image was specified and none was available from
       ## the build environment; build GCL from OpenAxiom source.
       ## User may explicilty specify --enable-gcl, but may be missing
       ## the dependency tarball.
       if test ! -d ${srcdir}/gcl; then
          AC_MSG_ERROR([The OpenAxiom dependency tarball is missing; please get it from our website.])
       fi
       AXIOM_LISP='$(axiom_build_bindir)/gcl'
       axiom_all_prerequisites="$axiom_all_prerequisites all-gcl"
       axiom_include_gcl=yes
       axiom_lisp_flavor=gcl
       axiom_fasl_type=o
       ;;
    yes,*)
       AC_MSG_ERROR([--with-lisp=$axiom_lisp conflicts with --enable-gcl])
       ;;
    *)
       ## As of this writting, the Lisp systems ECL, GCL, SBCL, and CLisp all
       ## exist at the end of standard input.
       AC_MSG_CHECKING([which flavor of Lisp])
       what=`echo '(lisp-implementation-type)' | $axiom_lisp`
       case $what in
	   *GCL*) 
	       axiom_lisp_flavor=gcl
	       ;;
	   *"ECL"*) 
	       axiom_lisp_flavor=ecl 
	       oa_standard_linking=yes
	       ;;
	   *"SBCL"*) 
	       axiom_lisp_flavor=sbcl 
	       ;;
	   *"CLISP"*)
               ## Not all variants of CLisp have FFI support.  FFI is used
               ## internally used by OpenAxiom in essential way.
               if ! $axiom_lisp -q -x '*features*' | grep ':FFI' > /dev/null
               then
                 AC_MSG_ERROR([$axiom_lisp does not support Foreign Function Interface.  Please upgrade to a better version of CLisp or install SBCL.])
               fi
	       axiom_lisp_flavor=clisp
	       ;;
	   *"Armed Bear Common Lisp"*) 
	       axiom_lisp_flavor=abcl 
	       ;;
           *"Clozure Common Lisp"*)
               axiom_lisp_flavor=clozure
               ;;
       esac
       AC_MSG_RESULT([$axiom_lisp_flavor])
esac

AC_SUBST(axiom_include_gcl)
AC_SUBST(axiom_lisp_flavor)
AC_SUBST(oa_standard_linking)
AC_DEFINE_UNQUOTED([OPENAXIOM_BASE_RTS],
                   [openaxiom_${axiom_lisp_flavor}_runtime],
                   [The kind of base runtime system for this build.])

## The following is a horrible hack to arrange for GCL to successfully
## rebuild symbol tables with "rsym" on Windows platform.  It should
## go away as soon as GCL upstream is fixed.
case $axiom_lisp_flavor,$target in
    gcl,*mingw*)
        axiom_gcl_rsym_hack='d=`echo "(format nil \"~a\" si::*system-directory*)" | $(AXIOM_LISP) | grep "/gcl.*/" | sed -e "s,\",,g"`; cp $$d/rsym$(EXEEXT) .'
	;;
    *) 
        ## Breath.
        axiom_gcl_rsym_hack=':'
	;;
esac
AC_SUBST(axiom_gcl_rsym_hack)


## If we are using GCL as the base runtime system, then we do really need
# a C compiler from GNU.  Well, at least for the moment.
case $axiom_lisp_flavor,$GCC in
   gcl,yes)
       axiom_cflags="-O2 -Wall -D_GNU_SOURCE"
       ;;
   
   gcl,*)
       AC_MSG_ERROR([We need a GNU C compiler])
       ;;
esac
AC_SUBST(axiom_cflags)

@

\paragraph{Lisp system options.}  Lisp implementations greatly vary in
the command line options they support.  Here we attempt to abstract
over those variations of Lisp systems we plan to support.  In particular,
we need to know how to iinvoke a Lisp compiler with a set of
files to process in batch mode.
<<lisp options>>=
## Can we use dynamically linked libraries?  
## Tentatively answer `yes' -- this is modern time.
oa_use_dynamic_lib=yes

## How are we supposed to tell the Lisp system to eval an expression
## in batch mode?  What is the extension of a compiled Lisp file?
case $axiom_lisp_flavor in
    gcl) 
       axiom_quiet_flags='-batch'
       axiom_eval_flags='-eval'
       oa_use_dynamic_lib=no  
       ;;
    ecl) 
       axiom_quiet_flags=
       axiom_eval_flags='-norc -eval'
       oa_use_dynamic_lib=no  
       ;;
    sbcl) 
       axiom_quiet_flags='--noinform --noprint'
       axiom_eval_flags='--eval'
       ;;
    clisp) 
       axiom_quiet_flags='--quiet'
       axiom_eval_flags='-norc -x'
       ;;
    clozure)
       axiom_quiet_flags='--quiet --no-init'
       axiom_eval_flags='--eval'
       ;;
    *) AC_MSG_ERROR([We do not know how to build OpenAxiom this $axiom_lisp]) ;;
esac
AC_SUBST(axiom_quiet_flags)
AC_SUBST(axiom_eval_flags)
AC_SUBST(oa_use_dynamic_lib)
@

\paragraph{Compiled Lisp file extensions.}
The file extension for compiled Lisp files is implementation defined.
There does not seem to have an established existing practice as would
be found in the majority of Unix world.  Consequently we need to
determine that by looking at the Lisp type of the pathname that
Lisp's [[compile-file]] would produce.
<<compiled lisp extension>>=
if test -z $axiom_fasl_type; then
    AC_MSG_CHECKING([compiled Lisp file extension])
    ## We set the IFS to <space> as we don't want automatic
    ## replacement of <newline> by <space>.
    axiom_save_IFS=$IFS
    IFS=' '
    axiom_fasl_type=`$axiom_lisp $axiom_quiet_flags $axiom_eval_flags '(progn (format t "axiom_fasl_type=~a" (pathname-type (compile-file-pathname "foo.lisp"))) (quit))'`

    ## Now pull out the fasl type.  ECL has the habit of spitting noise
    ## about internal loading.  Therefore, we must look only for a line that
    ## begins with axiom_fasl_type.
    axiom_fasl_type=`echo $axiom_fasl_type | grep '^axiom_fasl_type'`
    IFS=$axiom_save_IFS
    axiom_fasl_type=`echo $axiom_fasl_type | sed -e 's/axiom_fasl_type=//'`
    if test -z $axiom_fasl_type; then
	AC_MSG_ERROR([Could not determine extension for compiled Lisp files])
    fi
    AC_MSG_RESULT([$axiom_fasl_type])
fi
AC_SUBST(axiom_fasl_type)
@

\paragraph{Native data types}
OpenAxiom needs to communicate to the hosting operation systems
through a set of C interface.  Consequently we need an automated
translation mechanism that shields Boot code from the variability
of Lisp systems for so-called `foreign function interface'.  Here,
we compute a translation table for supported Lisp systems. This table
is used by the Boot translator for generating codes for import of
native routines.
<<nativeTypeTable>>=
case $axiom_lisp_flavor in
   gcl)
      void_type='void'
      char_type='char'
      int_type='int'
      float_type='float'
      double_type='double'
      string_type='string'
      ;;
   sbcl)
      void_type='void'
      char_type='char'
      int_type='int'
      float_type='float'
      double_type='double'
      string_type='c-string'
      ;;
   clisp)
      void_type='nil'
      char_type='character'
      int_type='int'
      float_type='single-float'
      double_type='double-float'
      string_type='c-string'
      ;;
   ecl)
      void_type=':void'
      char_type=':char'
      int_type=':int'
      float_type=':float'
      double_type=':double'
      string_type=':cstring'
      ;;
   clozure)
      void_type=':void'
      # FIXME: this is not really what we want, but good enough for now.
      char_type=':unsigned-byte'
      int_type=':signed-fullword'
      float_type=':single-float'
      double_type=':double-float'
      # Clozure CL wants you to deal with your own mess
      string_type=':address'
      ;;
   *)
      AC_MSG_ERROR([We do not know how to translate native types for this Lisp])
      ;;
esac
AC_SUBST(void_type)
AC_SUBST(char_type)
AC_SUBST(int_type)
AC_SUBST(float_type)
AC_SUBST(double_type)
AC_SUBST(string_type)

@


\section{Configuration options}
\label{sec:config-options}

We strive for making \Tool{OpenAxiom}'s build system integrate as seamlessly as 
possibly into the standard GNU build framework.

\subsection{Standard options}
\label{sec:config-options:std}

At the moment, we honor the following options:
\begin{description}
\item \verb!--prefix!:
  By default, \Tool{OpenAxiom}'s build system will install files 
  in ``\File{/usr/local}''.  However, you 
  can select a different location prefix using this option.

\item \verb!--with-x!:

\item \verb!--x-includes=DIR!

\item \verb!--x-libraries=DIR!

\item \verb!--help!

\item \verb!--version!
\end{description}


\subsection{\Tool{OpenAxiom}-specific options}
\label{sec:config-options:axiom-specific}

\begin{description}
\item \verb!--enable-gcl!:
  \Tool{OpenAxiom} needs an implementation of Lisp to support its
  runtime system.  At the moment, GNU Common Lisp (\Tool{GCL} for short)
  is used.  This options instructs \Tool{OpenAxiom} to build its own copy
  of \Tool{GCL}.  Use \verb!--disable-gcl! to prevent OpenAxiom
  from building \Tool{GCL}.

\item \verb!--with-lisp=L!:  
  instructs \Tool{OpenAxiom} to use the Lisp image [[L]] for its 
  runtime platform.

\item \verb!--enable-checking!:
  instructs \Tool{OpenAxiom}'s Lisp image to perform runtime checking
  for generated Lisp codes.
\end{description}

\section{Basic Setup}
\label{sec:basic-setup}

\subsection{\Tool{Autoconf} Initialization}
\label{sec:basic-setup:init}

The \Tool{Autoconf} machinery needs to be initialized with several pieces of
information:
\begin{itemize}
\item the \emph{name} of the system --- ``OpenAxiom 1.2.0''
\item its \emph{version}.  I choose to use the date of last checkin.
  It should probably include the revision number so as to 
  unambiguously identify which \Tool{OpenAxiom} flavour du jour is being
  built;
\item and where to send feedback, \emph{e.g.} bug reports.  At the moment, 
  we use
  the \email{open-axiom-devel} list.  That could change in the future if
  we reach a high volume traffic.  For the moment, we don't seem to
  suffer from traffic...
\end{itemize}
<<Autoconf init>>=
sinclude(config/open-axiom.m4)
sinclude(config/aclocal.m4)
AC_INIT([OpenAxiom], [1.4.0-2010-02-11], 
        [open-axiom-bugs@lists.sf.net])

@

\Tool{Autoconf} needs some auxilary files that are present in the 
sub-directory \File{config}:
<<Autoconf init>>=
AC_CONFIG_AUX_DIR(config)
AC_CONFIG_MACRO_DIR(config)
@

Not all platforms present the same operating system API to applications.
For the part of \Tool{OpenAxiom} written in the C programming language, we 
can collect, in a single file, variabilities in operating system 
API in form of C preprocessor macros.  That file is for the most part
automatically generated by \Tool{Autoheader}.
<<Autoconf init>>=
AC_CONFIG_HEADERS([config/openaxiom-c-macros.h])
@

Note that at configuration time, \Tool{configure} will instantiate a
file \File{config/openaxiom-c-macros.h} in the directory [[$(top_builddir)]],
appropriate for all C sub-parts of \Tool{OpenAxiom} to include.


Notice that since we don't use Automake (yet), we don't initialize
the Automake subsystem.  
<<Autoconf init>>=
# AM_INIT_AUTOMAKE([foreign])
@

We require Autoconf $2.62$ or higher from the developer part. Please,
note that this is no requirement on the user build environment.  All,
it means is that if someone makes changes to the current \File{configure.ac}
file, that someone needs to have Autoconf $2.62$ or higher to process this
file in order to regenerate \File{configure}.
<<Autoconf init>>=
AC_PREREQ([2.62])
@


\subsection{Source tree sanity check}
\label{sec:basic-setup:sanity-check}

The \Tool{Autoconf} system implements a very basic, simple-minded, 
sanity check
whereby it will refuse to run \File{configure} if the source tree does
not contain a specified file, that serves a witness for a bona fide source
tree.  Here, we use \File{Makefile.pamphlet} from the \File{src}
subdirectory.
<<sanity check>>=
AC_CONFIG_SRCDIR(src/Makefile.pamphlet)
@


\subsubsection{Instantiating configuration files}

<<instantiate config files>>=
AXIOM_MAKEFILE([Makefile])
AXIOM_MAKEFILE([src/Makefile])
AXIOM_MAKEFILE([src/lib/Makefile])
AXIOM_MAKEFILE([src/hyper/Makefile])
AXIOM_MAKEFILE([src/driver/Makefile])
AXIOM_MAKEFILE([src/lisp/Makefile])
AXIOM_MAKEFILE([src/boot/Makefile])
AXIOM_MAKEFILE([src/interp/Makefile])
AXIOM_MAKEFILE([src/share/Makefile])
AXIOM_MAKEFILE([src/algebra/Makefile])
AXIOM_MAKEFILE([src/input/Makefile])
AXIOM_MAKEFILE([src/etc/Makefile])
AXIOM_MAKEFILE([src/doc/Makefile])

AC_CONFIG_FILES([src/hyper/presea], [chmod +x src/hyper/presea])


## We now generate the "document" script and support files at configure time.
## We put them in the build directory because they are intended to be 
## build support utils only.
AC_CONFIG_FILES(build/scripts/document:$srcdir/src/scripts/document.in, \
                [chmod +x build/scripts/document])

AC_OUTPUT

## Generate rules to extrad SPAD type definitions from pamphlets.
echo -n "extracting list of SPAD type definitions..."
egrep '@<<(category|domain|package) .*>>=' \
    $srcdir/src/algebra/*.spad.pamphlet \
    | sort | uniq | \
    while IFS=':' read spad_file chunk_desc; do 
	chunk_desc=`echo $chunk_desc | sed -e 's,@<<,,' -e 's,>>=,,'`
	set $chunk_desc; spad_abbrev=$2
	cat >> src/algebra/tmp-extract-spad.mk <<EOF
$spad_abbrev.spad: \$(srcdir)/`basename $spad_file` ; \
    @\$(axiom_build_document) --output=\$@.tmp --tangle="$chunk_desc" \$< && \
    \$(top_confdir)/move-if-change \$@.tmp \$@
EOF
    done 
echo done
$srcdir/config/move-if-change \
    src/algebra/tmp-extract-spad.mk src/algebra/extract-spad.mk

@

\section{Dynamic and shared libraries}

We need to link some C object files into in the Lisp images we
use.  Some Lisps (e.g. GCL, ECL) support inclusion of ``ordinary''
object files.  Other Lisps (e.g. SBCL) support only dynamic
or shared libraries.  However, the exact minutia of  portably
building shared libraries are known to be fraught with all kinds
of traps.  Consequently, dedicated tools have been developed to
abstract away from those details.  In particular, we rely on
GNU \Tool{libtool} to take care of that for us.
<<initialize shared libraries tool>>=
oa_use_libtool_for_shared_lib=yes
oa_shrobj_flags=
oa_shrlib_flags=
# Tell Libtool to assume `dlopen' so that it does not have to
# emulate it.
LT_INIT([pic-only dlopen win32-dll shared])
AC_SUBST([LIBTOOL_DEPS])
# Give me extension of libraries
eval shared_ext=\"$shrext_cmds\"
AC_SUBST(shared_ext)
AC_SUBST(libext)
## Don't use Libtool for building actual DLLs on MinGW and Cygwin
## Libool has been improved to the point of being useless
## for building in-place shared libraries.
oa_use_libtool_for_shared_lib=no
case $host in
    *mingw*|*cygwin*)
       # oa_use_libtool_for_shared_lib=no
       oa_shrobj_flags='-prefer-pic'
       oa_shrlib_flags="-shared --export-all-symbols"
       ;;
    *darwin*)
       oa_shrobj_flags='-dynamic'
       oa_shrlib_flags='-dynamiclib -undefined suppress -flat_namespace'
       ;;
    *)
       oa_shrobj_flags='-prefer-pic'
       oa_shrlib_flags='-shared'
       ;;
esac
AC_SUBST(oa_use_libtool_for_shared_lib)
AC_SUBST(oa_shrobj_flags)
AC_SUBST(oa_shrlib_flags)
@

\section{configure.ac}

<<*>>=
<<Autoconf init>>
<<sanity check>>
<<host build target platfoms>>
<<find C compiler>>

<<initialize shared libraries tool>>

axiom_src_subdirs="lib hyper lisp boot interp share algebra input etc doc"
AC_SUBST(axiom_src_subdirs)

## On Windows system, we prefer the default installation
## location to be 'C:/Program Files/OpenAxiom', following Windows 
## convention.  We cannot use AC_PREFIX_DEFAULT directly as it seems 
## to operate unconditionally.  Therefore, we resort to this dirty
## trick stepping over Autoconf's internals.
case $host in
    *mingw*)
        ac_default_prefix="C:/Program Files/OpenAxiom"
        AC_PATH_PROGS([oa_editor],[notepad.exe])
	;;
    *)  
        AC_PATH_PROGS([oa_editor],[vi])
        ;;
esac
AC_SUBST(oa_editor)

<<build utils>>
<<runtime checking>>

# FIXME: Move this out of here.  
axiom_c_runtime=
AC_SUBST(axiom_c_runtime)

<<C headers and libraries>>

<<platform specific bits>>
<<nativeTypeTable>>
<<instantiate config files>>
echo "Type '${MAKE}' (without quotes) to build OpenAxiom"
@


\section{A note about comments}
\label{sec:comment}

This is a pamphlet file.  That means the source code embedded here 
are first extracted into a form (\File{configure.ac}) digestible by
\Tool{Autoconf}, which in turn produces the end-user \File{configure}
script run for setting up the build.

\Tool{Autoconf} supports two kinds of comments:
\begin{enumerate}
\item [[dnl]] style, and
\item [[#]] style.
\end{enumerate}
Comments introduced with [[dnl]] are copied verbatim to the generated
\File{configure.ac}; however, do not appear in the \File{configure}
output file.  They are for \Tool{Autoconf} consumption only --- and that
of the humans reading \File{configure.ac} (ideally, there should be none).
Comments starting with [[#]] appear verbatim in both \File{configure.ac}
and \File{configure} files.  Because this is a pamphlet file, there almost 
never is a need to use the [[dnl]]-style comment.  
Consequently, \Tool{Autoconf} comments in this file should be
of [[#]]-style form.  Such comments can be of value to the occasional
poor masochist who will be debugging the generated \File{configure}.


\end{document}