configure.ac

#*****************************************************************************
#       Copyright (C) 2005-2007 William Stein
#                     2009-2011 David Kirkby
#                     2012-2015 Volker Braun
#                     2012-2019 Jeroen Demeyer
#                     2014-2017 François Bissey
#                     2016-2022 Matthias Koeppe
#                     2017-2018 Erik M. Bray
#                     2018      Dima Pasechnik
#                     2020      Jonathan Kliem
#                     2021-2023 Michael Orlitzky
#
# This program 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, either version 2 of the License, or
# (at your option) any later version.
#                  http://www.gnu.org/licenses/
#*****************************************************************************

dnl If you are going to update this, please stick the recommended layout
dnl in the autoconf manual - i.e.

dnl First check for programs
dnl Next check for libraries
dnl Next check for header files
dnl Next check for types
dnl Next check for structures
dnl Next check compiler characteristics
dnl Next check for library functions
dnl Next check for system services

dnl Older versions do not support $GFC
AC_PREREQ([2.69])

AC_DEFUN([SAGE_VERSION], m4_esyscmd_s([. src/bin/sage-version.sh && echo $SAGE_VERSION]))
AC_INIT([Sage], SAGE_VERSION, [sage-devel@googlegroups.com])


AC_COPYRIGHT([GPL version 3])
AC_CONFIG_SRCDIR([configure.ac])
AC_CONFIG_AUX_DIR([config])

dnl This is the hierarchy where everything gets installed (SAGE_LOCAL).
dnl By default, it is the subdirectory local, but the user
dnl can override it by supplying --prefix=....
AC_PREFIX_DEFAULT(`pwd -P`/local)

dnl We don't really use automake, but configure needs aclocal and the
dnl automake library files (like config.guess).
AM_INIT_AUTOMAKE([1.9.6 foreign])

# Allow "configure --disable-maintainer-mode" to disable timestamp checking
AM_MAINTAINER_MODE([enable])

dnl Make sure the path to our own m4 macros is always properly set
dnl and doesn't depend on how autoconf is called.
AC_CONFIG_MACRO_DIR([m4])

dnl The AC_LIB_RPATH macro comes from a Gnulib-provided file in m4/.
dnl It defines, among other things, the $acl_shlibext variable that
dnl contains the shared library extension for this system. We already use the
dnl AM_ICONV macro from the same source (which ultimately calls AC_LIB_RPATH), and we
dnl avoid involving libtool by using it to get the shared library extension.
AC_LIB_RPATH
AC_SUBST(SHLIBEXT, "${acl_shlibext}")

########################################################################
# Set various environment variables (needed at configure time)
########################################################################

# Assume current directory is SAGE_ROOT.
SAGE_ROOT=`pwd -P`
AC_SUBST(SAGE_ROOT)

SAGE_LOCAL="$prefix"
# The following line is necessary because the code below
# inspects stuff in the installation prefix at configure time.
# This is nonstandard.
if test "$SAGE_LOCAL" = NONE; then
    SAGE_LOCAL=local
    if test -x "$SAGE_LOCAL"/bin/python3; then
        # Incremental build with an existing installation of python3 spkg
        # in SAGE_LOCAL or venv in SAGE_LOCAL.  Keep old behavior.
        SAGE_VENV_AUTO=no
    else
        SAGE_VENV_AUTO=yes
    fi
else
    SAGE_VENV_AUTO=no
fi
SAGE_SRC="$SAGE_ROOT/src"

AC_ARG_WITH([sage-venv],
            [AS_HELP_STRING([--with-sage-venv={auto (default),yes,no,SAGE_VENV}],
                            [put Python packages into an installation hierarchy separate from prefix])],
            [SAGE_VENV="$withval"],
            [SAGE_VENV="auto"])
AC_SUBST([SAGE_VENV])

AC_SUBST([SAGE_DOCS], ['${SAGE_LOCAL}'])dnl Quoted so that it is resolved at build time by shell/Makefile

#---------------------------------------------------------

AC_ARG_ENABLE([build-as-root],
              [AS_HELP_STRING([--enable-build-as-root],
                              [allow building Sage as root (for use in containers)])],
              [enable_build_as_root=$enableval],
              [enable_build_as_root=no])
if test "$enable_build_as_root" != yes; then
   AX_CHECK_ROOT([AC_MSG_ERROR([You cannot build Sage as root, switch to an unprivileged user.  (If building in a container, use --enable-build-as-root.)])], [])
fi

AC_ARG_ENABLE([fat-binary],
              [AS_HELP_STRING([--enable-fat-binary],
                              [build binaries that will run on the widest range of target CPUs (but not relocatable)])],
              [AC_SUBST(SAGE_FAT_BINARY, "yes")],
              [])

AC_ARG_VAR(SAGE_FAT_BINARY, set to "yes" to build binaries that will run on the widest range of target CPUs (but not relocatable))

AC_ARG_ENABLE([debug],
              [AS_HELP_STRING([--enable-debug={no|symbols|yes}],
                              [controls debugging support: "no" debugging; debugging "symbols" (default); build debug version ("yes")])],
              [AC_SUBST(SAGE_DEBUG, $enableval)],
              [])

AC_ARG_VAR(SAGE_DEBUG, controls debugging support: "no" debugging; debugging "symbols" (default); build debug version ("yes"))

AC_ARG_ENABLE([editable],
              [AS_HELP_STRING([--disable-editable],
                              [do not use an editable install of the Sage library: changes to Python files will require "sage -b" to rebuild the Sage library])],
              [AC_SUBST([SAGE_EDITABLE], [$enableval])],
              [AC_SUBST([SAGE_EDITABLE], [yes])])

AC_ARG_ENABLE([wheels],
              [AS_HELP_STRING([--enable-wheels],
                              [build wheels for the Sage library and update them on "sage -b"; if disabled, use "make wheels" to build wheels])],
              [dnl
                 AS_VAR_IF([SAGE_EDITABLE], [yes], [dnl
                 ], [dnl
                   AC_MSG_NOTICE([direct installation of the Sage library (--disable-editable --disable-wheels) is no longer supported; ignoring --disable-wheels])
                 ])
                 AC_SUBST([SAGE_WHEELS], [$enableval])
              ], [dnl
                 AS_VAR_IF([SAGE_EDITABLE], [yes], [dnl
                   AC_SUBST([SAGE_WHEELS], [no])
                 ], [dnl
                   AC_SUBST([SAGE_WHEELS], [yes])
                 ])
              ])

# Check whether we are on a supported platform
AC_CANONICAL_BUILD()
AC_CANONICAL_HOST()

case $host in
dnl The following are all supported platforms.
*-*-freebsd*);;
*-*-linux*);;
*-*-darwin*);;

dnl Wildcard for unsupported platforms
*)
AC_MSG_ERROR([[
You are attempting to build Sage on $host,
which is not a supported platform for Sage]]);;
esac

dnl Issue #38039: Alert users on WSL early about a source tree
dnl that has not been cloned correctly.
dnl This will save users from running into build errors later.
AC_MSG_CHECKING([the symbolic links in the source tree])
AS_IF([test -L build/pkgs/liblzma/package-version.txt], [dnl OK
    AC_MSG_RESULT([intact])
], [dnl Either replaced by a copy (OK, as done in the sage-conf_pypi sdist)
    dnl  or replaced by the name of the link target (BAD, misconfigured git clone in WSL)
    AS_IF([test ! -e build/pkgs/sagelib/src], [dnl
        AC_MSG_RESULT([intact (with links to embedded source trees pruned)])
    ], [dnl
        AS_IF([test -d build/pkgs/sagelib/src], [dnl
            AC_MSG_RESULT([broken (links to directories have been replaced by copies)])
        ], [dnl
            AC_MSG_RESULT([broken])
        ])
        AC_MSG_NOTICE([Sorry, the symbolic links in this source tree are broken.])
        AC_MSG_NOTICE([See README.md for installation instructions.])
        AC_MSG_ERROR([Exiting, as Sage cannot be built from this source tree.])
    ])
])

###############################################################################
# Check general programs
###############################################################################

AC_PROG_SED

AC_CHECK_PROG(found_ar, ar, yes, no)
if test x$found_ar != xyes
then
    AC_MSG_NOTICE([Sorry, the 'ar' command must be in the path to build AC_PACKAGE_NAME])
    AC_MSG_NOTICE([On some systems it can be found in /usr/ccs/bin ])
    AC_MSG_NOTICE(['ar' is also part of the GNU 'binutils' package.])
    AC_MSG_ERROR([Exiting, as the archiver 'ar' can not be found.])
fi

AC_CHECK_PROG(found_m4, m4, yes, no)
if test x$found_m4 != xyes
then
    AC_MSG_NOTICE([Sorry, the 'm4' command must be in the path to build AC_PACKAGE_NAME])
    AC_MSG_NOTICE([On some systems it can be found in /usr/ccs/bin])
    AC_MSG_NOTICE([See also http://www.gnu.org/software/m4/])
    AC_MSG_ERROR([Exiting, as the macro processor 'm4' can not be found.])
fi

m4_ifndef([PKG_PROG_PKG_CONFIG], [m4_errprint(
[Error: could not locate the pkg-config autoconf macros. These are
usually located in /usr/share/aclocal/pkg.m4. If your macros are
in a different location, try setting the environment variable
ACLOCAL="aclocal -I/other/macro/dir" before running ./bootstrap
])
dnl Exit autoconf with exit code 16 in this case. This will be
dnl caught by the bootstrap script.
m4_exit(16)])

PKG_PROG_PKG_CONFIG([0.29])

AC_CHECK_PROG(found_ranlib, ranlib, yes, no)
if test x$found_ranlib != xyes
then
    AC_MSG_NOTICE([Sorry, the 'ranlib' command must be in the path to build AC_PACKAGE_NAME])
    AC_MSG_NOTICE([On some systems it can be found in /usr/ccs/bin ])
    AC_MSG_NOTICE(['ranlib' is also part of the GNU 'binutils' package.])
    AC_MSG_ERROR([Exiting, as 'ranlib' can not be found.])
fi

AC_CHECK_PROG(found_strip, strip, yes, no)
if test x$found_strip != xyes
then
    AC_MSG_NOTICE([Sorry, the 'strip' command must be in the path to build AC_PACKAGE_NAME])
    AC_MSG_NOTICE([On some systems 'strip' can be found in /usr/ccs/bin ])
    AC_MSG_NOTICE(['strip' is also part of the GNU 'binutils' package.])
    AC_MSG_ERROR([Exiting, as 'strip' can not be found.])
fi

# Check tar
AC_CACHE_CHECK([for GNU or BSD tar], [ac_cv_path_TAR], [
AC_PATH_PROGS_FEATURE_CHECK(TAR, [tar gtar], [[
ac_version_TAR=`$ac_path_TAR --version 2>&1`
if echo "$ac_version_TAR" | grep >/dev/null GNU; then
    ac_cv_path_TAR=$ac_path_TAR
    if test $ac_prog = tar; then
        ac_path_TAR_found=:
    fi
fi
if echo "$ac_version_TAR" | grep >/dev/null bsdtar; then
    ac_cv_path_TAR=$ac_path_TAR
    if test $ac_prog = tar; then
        ac_path_TAR_found=:
    fi
fi
]],
[AC_MSG_ERROR([could not find either a GNU or BSD version of tar])],
[$PATH:/usr/sfw/bin])
])

command_TAR=`command -v tar 2>/dev/null`
AS_IF([test x$command_TAR != x$ac_cv_path_TAR],
      [AC_MSG_ERROR([[found a good version of tar in $ac_cv_path_TAR, but it's not the first "tar" program in your PATH]])]
)

# Check make (unless MAKE is set)
if test -z "$MAKE"; then
    AC_CACHE_CHECK([for GNU make], [ac_cv_path_MAKE], [
    AC_PATH_PROGS_FEATURE_CHECK(MAKE, [make gmake], [[
    ac_version_MAKE=`$ac_path_MAKE --version 2>&1`
    if echo "$ac_version_MAKE" | grep >/dev/null GNU; then
        ac_cv_path_MAKE=$ac_path_MAKE
        if test $ac_prog = make; then
            ac_path_MAKE_found=:
        fi
    fi
    ]],
    [AC_MSG_ERROR([could not find a GNU version of make])],
    [$PATH:/usr/sfw/bin])
    ])

    command_MAKE=`command -v make 2>/dev/null`
    AS_IF([test x$command_MAKE != x$ac_cv_path_MAKE],
          [AC_MSG_ERROR([[found GNU make in $ac_cv_path_MAKE, but it's not the first "make" program in your PATH]])])
fi

# Check for system python
AC_MSG_CHECKING([for Python])
if SAGE_BOOTSTRAP_PYTHON=$(build/bin/sage-bootstrap-python -c "import sys; print(sys.executable)"); then
    AC_MSG_RESULT([$SAGE_BOOTSTRAP_PYTHON])
else
    AC_MSG_ERROR([You do not have a suitable version of Python installed])
fi

# Check that perl is available, with version 5.8.0 or later.
# Some packages need perl, however it is not clear whether Sage really
# requires version >= 5.8.0.  The R package *used* to require it, but
# not anymore. -- Jeroen Demeyer
AC_PATH_PROG([PERL],[perl])
AX_PROG_PERL_VERSION([5.8.0],[],[
    AC_MSG_ERROR([Exiting, since AC_PACKAGE_NAME requires perl-5.8.0 or later])
])

###############################################################################
# Check C/C++/Fortran compilers
###############################################################################

# Save compiler flags as configured by the user.
# We have to redo this, because otherwise `AC_PROG_CC` will just overwrite them.
AC_SUBST(CFLAGS, "$CFLAGS")
AC_SUBST(CXXFLAGS, "$CXXFLAGS")
AC_SUBST(FCFLAGS, "$FCFLAGS")
AC_SUBST(F77FLAGS, "$F77FLAGS")
AC_ARG_VAR(CFLAGS, C compiler flags)
AC_ARG_VAR(CXXFLAGS, C compiler flags)
AC_ARG_VAR(FCFLAGS, Fortran compiler flags)
AC_ARG_VAR(F77CFLAGS, Fortran 77 compiler flags)

SAGE_CHECK_CONDA_COMPILERS

AC_PROG_CC()
AC_PROG_CPP()
AC_PROG_CXX()
AC_PROG_FC()

AC_SUBST(CC)
AC_SUBST(FC)

# On darwin, also set the objective C/C++ compilers
# Checking on all platforms doesn't hurt and stops
# configure from sending an error when run on non-darwin.
AC_PROG_OBJC()
AC_PROG_OBJCXX()
AC_SUBST(OBJC)
AC_SUBST(OBJCXX)

AS_IF([test "x$CXX" = x], [AC_MSG_ERROR([a C++ compiler is missing])])


###############################################################################
# Check header files
###############################################################################


# complex.h is one that might not exist on older systems.
AC_LANG(C++)
AC_CHECK_HEADER([complex.h],[],[
    AC_MSG_ERROR([Exiting, since you do not have the 'complex.h' header file.])
])


###############################################################################
# Check libraries
###############################################################################

# First check for something that should be in any maths library (sqrt).
AC_LANG(C++)
AC_CHECK_LIB(m,sqrt,[],[
                       AC_MSG_ERROR([Exiting, since a maths library was not found.])
                       ])

# Check that we are not building in a directory containing spaces
AS_IF([echo "$ac_pwd" |grep " " >/dev/null],
      AC_MSG_ERROR([the path to the Sage root directory ($ac_pwd) contains a space. Sage will not build correctly in this case])
)

###############################################################################
# Collect substitutions for build/make/Makefile.in
###############################################################################

# $(TOOLCHAIN) variable containing prerequisites for the build
SAGE_TOOLCHAIN=gcc
if test "$SAGE_INSTALL_CCACHE" = yes ; then
    SAGE_TOOLCHAIN="$SAGE_TOOLCHAIN ccache"
fi
AC_SUBST([SAGE_TOOLCHAIN])

AC_ARG_ENABLE([experimental-packages],
  [AS_HELP_STRING([--enable-experimental-packages],
    [allow installing experimental packages (default: no = ask for user confirmation for each package)])])
AC_ARG_ENABLE([download-from-upstream-url],
  [AS_HELP_STRING([--disable-download-from-upstream-url],
    [disallow downloading packages from their upstream URL if they cannot be found on the Sage mirrors])], [],
    [AS_VAR_SET([enable_download_from_upstream_url], [yes])])

AC_ARG_ENABLE(
  [system-site-packages], [AS_HELP_STRING(
    [--enable-system-site-packages],
    [allow the use of python packages from the system (experimental; default: no)]
  )], [
  AS_IF([test "x$enable_system_site_packages" = "xyes"], [
    dnl When installing python SPKGs in the presence of system-site
    dnl packages, we need to --ignore-installed so that a patched SPKG
    dnl can be installed in the presence of an unpatched system package
    dnl that appears (to pip) to be identical. The --no-deps flag is
    dnl then needed because --ignore-installed will make any installed
    dnl dependencies invisible to pip, who does not appreciate that.
    SAGE_PIP_INSTALL_FLAGS="${SAGE_PIP_INSTALL_FLAGS} --no-deps --ignore-installed"

    SAGE_VENV_FLAGS="${SAGE_VENV_FLAGS} --system-site-packages"

    dnl We want to raise an error if the user asked for "system site
    dnl packages" but the system python will not be used. Technically
    dnl that causes no problems (SAGE_PYTHON_PACKAGE_CHECK always fails,
    dnl so SPKGs are used for all python packages), but it may be confusing
    dnl to end users who expect the flag to actually give them access to
    dnl their system python packages and who may not be paying close
    dnl attention to their ./configure output.
    with_system_python3="force"

    dnl This is substituted in to build/bin/sage-build-env-config.in for use
    dnl by build/bin/sage-get-system-packages
    ENABLE_SYSTEM_SITE_PACKAGES=yes
  ])
])
AC_SUBST([ENABLE_SYSTEM_SITE_PACKAGES])
AC_SUBST([SAGE_PIP_INSTALL_FLAGS])
AC_SUBST([SAGE_VENV_FLAGS])

SAGE_SPKG_OPTIONS=""
AS_IF([test "x$enable_experimental_packages" = "xyes"], [
  AS_VAR_APPEND([SAGE_SPKG_OPTIONS], [" -y"])
])
AS_IF([test "x$enable_download_from_upstream_url" = "xyes"], [
  AS_VAR_APPEND([SAGE_SPKG_OPTIONS], [" -o"])
])
AC_SUBST([SAGE_SPKG_OPTIONS])

AC_ARG_ENABLE([sagelib],
  AS_HELP_STRING([--disable-sage_conf],
                 [disable build of the sage_conf package]), [
    for pkg in sage_conf; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
  ])

AC_ARG_ENABLE([cvxopt],
  AS_HELP_STRING([--disable-cvxopt],
                 [disable build of the cvxopt package and its prerequisite suitesparse]), [
    for pkg in cvxopt suitesparse; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
  ])

AC_ARG_ENABLE([notebook],
  AS_HELP_STRING([--disable-notebook],
                 [disable build of the Jupyter notebook and related packages]), [
    for pkg in notebook nbconvert beautifulsoup4 sagenb_export nbformat nbclient terminado send2trash prometheus_client mistune pandocfilters bleach defusedxml jsonschema jupyter_jsmol argon2_cffi argon2_cffi_bindings webencodings tinycss2 ipympl soupsieve fastjsonschema anyio arrow async_lru fqdn isoduration json5 jsonpointer jsonschema_specifications jupyter_events jupyter_lsp jupyter_server jupyter_server_terminals jupyterlab jupyterlab_server jupyterlab_pygments jupyterlab_mathjax2 jupyter_sphinx notebook_shim overrides python_json_logger pyyaml referencing rfc3339_validator rfc3986_validator sniffio types_python_dateutil uri_template webcolors websocket_client httpx httpcore h11; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
  ])

AC_ARG_ENABLE([r],
  AS_HELP_STRING([--disable-r],
                 [disable build of the R package and related packages]), [
    for pkg in r rpy2 r_jupyter tzlocal pytz_deprecation_shim tzdata; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
  ])

AC_ARG_ENABLE([sagetex],
  AS_HELP_STRING([--disable-sagetex],
                 [don't build SageTeX]), [
    AS_VAR_SET([SAGE_ENABLE_sagetex], [$enableval])
  ])

AC_ARG_ENABLE([doc],
  AS_HELP_STRING([--disable-doc],
                 [disable build of the Sage documentation and packages depending on it]), [
    dnl Disable packages needed for docbuilding
    for pkg in sage_docbuild alabaster babel snowballstemmer imagesize sphinx sphinxcontrib_devhelp sphinxcontrib_jsmath sphinxcontrib_serializinghtml sphinxcontrib_applehelp sphinxcontrib_htmlhelp sphinxcontrib_qthelp sphinxcontrib_websupport jupyter_sphinx furo sphinx_copybutton sphinx_inline_tabs mathjax sphinx_basic_ng; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
    AS_VAR_IF([enableval], [no], [dnl Disable the docbuild by disabling the install tree for documentation
        AS_VAR_SET([SAGE_DOCS], [])dnl
    ])
  ])

AC_ARG_ENABLE([sagelib],
  AS_HELP_STRING([--disable-sagelib],
                 [disable build of the Sage library and packages depending on it]), [
    for pkg in sagelib sage_docbuild sage_setup; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
  ])


dnl Handle combinations of --disable-foo flags that may enable us to
dnl prune even more dependencies.
AS_IF([test "$SAGE_ENABLE_notebook" = no -a "$SAGE_ENABLE_sagelib" = no], [
    for pkg in jupyter_client ipykernel ipython zeromq pyzmq exceptiongroup; do
      AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
    done
  ])
AS_IF([test "$SAGE_ENABLE_r" = no -a "$SAGE_ENABLE_sage_docbuild" = no], [
  dnl pytz is needed only by rpy2 and babel, and babel is already
  dnl disabled by --disable-doc.
  for pkg in pytz; do
    AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
  done
])
AS_IF([test "$SAGE_ENABLE_r" = no -a "$SAGE_ENABLE_notebook" = no], [
  dnl These two are dependencies of both rpy2 and some notebook stuff
  for pkg in cffi pycparser; do
    AS_VAR_SET([SAGE_ENABLE_$pkg], [$enableval])
  done
])

dnl Packages that require a special override to use the SPKG
dnl when the system package is not usable.
AS_VAR_SET([sage_use_system_gcc], [force])

SAGE_SPKG_COLLECT()

AC_CONFIG_FILES([build/make/Makefile-auto build/make/Makefile])
AC_CONFIG_FILES([src/bin/sage-env-config src/bin/sage-src-env-config build/bin/sage-build-env-config])

AC_CONFIG_FILES([pkgs/sage-conf/_sage_conf/_conf.py])

dnl Create basic directories needed for Sage
AC_CONFIG_COMMANDS(mkdirs,
    [
        for d in "$SAGE_LOGS" "$SAGE_LOCAL" \
            "$SAGE_LOCAL/bin" "$SAGE_LOCAL/etc" \
            "$SAGE_LOCAL/include" "$SAGE_LOCAL/lib" \
            "$SAGE_LOCAL/lib/pkgconfig" \
            "$SAGE_SHARE" "$SAGE_LOCAL/var/lib/sage/installed"; do
                AC_MSG_NOTICE([creating directory $d])
                mkdir -p "$d" || AC_MSG_ERROR(could not create $d)
        done

        if test -d "$SAGE_LOCAL/lib64"; then
            if test ! -L "$SAGE_LOCAL/lib64"; then
                AC_MSG_NOTICE([[$SAGE_LOCAL/lib64 is not a symlink, see Issue #19782]])
                AC_MSG_ERROR([[Cannot perform incremental update, run "make distclean && make"]])
            fi
        else
            AC_MSG_NOTICE([[creating symbolic link lib64 -> lib]])
            ln -s lib "$SAGE_LOCAL/lib64"
        fi
        dnl Check that the file system is sufficiently functional
        if test -z "$SAGE_BUILD_DIR"; then
            SAGE_BUILD_DIR="$SAGE_LOCAL/var/tmp/sage/build"
        fi
        AC_MSG_NOTICE([creating directory $SAGE_BUILD_DIR])
        mkdir -p "$SAGE_BUILD_DIR" || AC_MSG_ERROR([error creating directory $SAGE_BUILD_DIR (SAGE_BUILD_DIR)])
        rm -f "$SAGE_BUILD_DIR"/conftest
        touch "$SAGE_BUILD_DIR"/conftest || AC_MSG_ERROR([error creating a file in $SAGE_BUILD_DIR])
        chmod +x "$SAGE_BUILD_DIR"/conftest || AC_MSG_ERROR([error setting file permissions +x in $SAGE_BUILD_DIR])
        test -x "$SAGE_BUILD_DIR"/conftest || AC_MSG_ERROR([file permissions +x did not persist in $SAGE_BUILD_DIR])
        chmod -x "$SAGE_BUILD_DIR"/conftest || AC_MSG_ERROR([error setting file permissions -x in $SAGE_BUILD_DIR])
        test -x "$SAGE_BUILD_DIR"/conftest && AC_MSG_ERROR([file permissions -x did not persist in $SAGE_BUILD_DIR])
        rm -f "$SAGE_BUILD_DIR"/conftest
    ],
    [
        SAGE_LOGS="$SAGE_ROOT/logs/pkgs"
        SAGE_LOCAL="$SAGE_LOCAL"
        SAGE_SHARE="$SAGE_LOCAL/share"
    ])

AC_CONFIG_COMMANDS(links, [
    dnl Create links for the convenience of users
    SYMLINK="${ac_top_build_prefix}prefix"
    AS_IF([test -L "$SYMLINK" -o ! -e "$SYMLINK"], [
        AC_MSG_NOTICE([creating convenience symlink $SYMLINK -> $SAGE_LOCAL])
        rm -f "$SYMLINK"
        ln -sf "$SAGE_LOCAL" "$SYMLINK"
    ], [
        AC_MSG_NOTICE([cannot create convenience symlink $SYMLINK -> $SAGE_LOCAL because the file exists and is not a symlink; this is harmless])
    ])
    SYMLINK="${ac_top_build_prefix}venv"
    AS_IF([test -L "$SYMLINK" -o ! -e "$SYMLINK"], [
        AC_MSG_NOTICE([creating convenience symlink $SYMLINK -> $SAGE_VENV])
        rm -f "$SYMLINK"
        ln -sf "$SAGE_VENV" "$SYMLINK"
    ], [
        AC_MSG_NOTICE([cannot create convenience symlink $SYMLINK -> $SAGE_VENV because the file exists and is not a symlink; this is harmless])
    ])
], [
    SAGE_LOCAL="$SAGE_LOCAL"
    eval SAGE_VENV="$SAGE_VENV"dnl eval so as to evaluate the embedded ${SAGE_LOCAL}
])

AC_OUTPUT()

SAGE_SYSTEM_PACKAGE_NOTICE()

dnl vim:syntax=m4