+#### Extract some information from the operating system and machine files.
+
+AC_CHECKING([the machine- and system-dependent files to find out
+ - which libraries the lib-src programs will want, and
+ - whether the GNU malloc routines are usable])
+
+### First figure out CFLAGS (which we use for running the compiler here)
+### and REAL_CFLAGS (which we use for real compilation).
+### The two are the same except on a few systems, where they are made
+### different to work around various lossages. For example,
+### GCC 2.5 on GNU/Linux needs them to be different because it treats -g
+### as implying static linking.
+
+### If the CFLAGS env var is specified, we use that value
+### instead of the default.
+
+### It's not important that this name contain the PID; you can't run
+### two configures in the same directory and have anything work
+### anyway.
+tempcname="conftest.c"
+
+echo '
+#include "'${srcdir}'/src/'${opsysfile}'"
+#include "'${srcdir}'/src/'${machfile}'"
+#ifndef LIBS_MACHINE
+#define LIBS_MACHINE
+#endif
+#ifndef LIBS_SYSTEM
+#define LIBS_SYSTEM
+#endif
+#ifndef C_SWITCH_SYSTEM
+#define C_SWITCH_SYSTEM
+#endif
+#ifndef C_SWITCH_MACHINE
+#define C_SWITCH_MACHINE
+#endif
+configure___ libsrc_libs=LIBS_MACHINE LIBS_SYSTEM
+configure___ c_switch_system=C_SWITCH_SYSTEM
+configure___ c_switch_machine=C_SWITCH_MACHINE
+
+#ifndef LIB_X11_LIB
+#define LIB_X11_LIB -lX11
+#endif
+
+#ifndef LIBX11_MACHINE
+#define LIBX11_MACHINE
+#endif
+
+#ifndef LIBX11_SYSTEM
+#define LIBX11_SYSTEM
+#endif
+configure___ LIBX=LIB_X11_LIB LIBX11_MACHINE LIBX11_SYSTEM
+
+#ifdef UNEXEC
+configure___ unexec=UNEXEC
+#else
+configure___ unexec=unexec.o
+#endif
+
+#ifdef SYSTEM_MALLOC
+configure___ system_malloc=yes
+#else
+configure___ system_malloc=no
+#endif
+
+#ifdef USE_MMAP_FOR_BUFFERS
+configure___ use_mmap_for_buffers=yes
+#else
+configure___ use_mmap_for_buffers=no
+#endif
+
+#ifndef C_DEBUG_SWITCH
+#define C_DEBUG_SWITCH -g
+#endif
+
+#ifndef C_OPTIMIZE_SWITCH
+#ifdef __GNUC__
+#define C_OPTIMIZE_SWITCH -O2
+#else
+#define C_OPTIMIZE_SWITCH -O
+#endif
+#endif
+
+#ifndef LD_SWITCH_MACHINE
+#define LD_SWITCH_MACHINE
+#endif
+
+#ifndef LD_SWITCH_SYSTEM
+#define LD_SWITCH_SYSTEM
+#endif
+
+#ifndef LD_SWITCH_X_SITE_AUX
+#define LD_SWITCH_X_SITE_AUX
+#endif
+
+configure___ ld_switch_system=LD_SWITCH_SYSTEM
+configure___ ld_switch_machine=LD_SWITCH_MACHINE
+
+#ifdef THIS_IS_CONFIGURE
+
+/* Get the CFLAGS for tests in configure. */
+#ifdef __GNUC__
+configure___ CFLAGS=C_DEBUG_SWITCH C_OPTIMIZE_SWITCH '${SPECIFIED_CFLAGS}'
+#else
+configure___ CFLAGS=C_DEBUG_SWITCH '${SPECIFIED_CFLAGS}'
+#endif
+
+#else /* not THIS_IS_CONFIGURE */
+
+/* Get the CFLAGS for real compilation. */
+#ifdef __GNUC__
+configure___ REAL_CFLAGS=C_DEBUG_SWITCH C_OPTIMIZE_SWITCH '${SPECIFIED_CFLAGS}'
+#else
+configure___ REAL_CFLAGS=C_DEBUG_SWITCH '${SPECIFIED_CFLAGS}'
+#endif
+
+#endif /* not THIS_IS_CONFIGURE */
+' > ${tempcname}
+
+# The value of CPP is a quoted variable reference, so we need to do this
+# to get its actual value...
+CPP=`eval "echo $CPP"`
+changequote(, )dnl
+eval `${CPP} -Isrc ${tempcname} \
+ | sed -n -e 's/^configure___ \([^=]*=\)\(.*\)$/\1"\2"/p'`
+if test "x$SPECIFIED_CFLAGS" = x; then
+ eval `${CPP} -Isrc -DTHIS_IS_CONFIGURE ${tempcname} \
+ | sed -n -e 's/^configure___ \([^=]*=\)\(.*\)$/\1"\2"/p'`
+else
+ REAL_CFLAGS="$CFLAGS"
+fi
+changequote([, ])dnl
+rm ${tempcname}
+
+ac_link="$ac_link $ld_switch_machine $ld_switch_system"
+
+### Make sure subsequent tests use flags consistent with the build flags.
+
+if test x"${OVERRIDE_CPPFLAGS}" != x; then
+ CPPFLAGS="${OVERRIDE_CPPFLAGS}"
+else
+ CPPFLAGS="$c_switch_system $c_switch_machine $CPPFLAGS"
+fi
+
+dnl Do this early because it can frob feature test macros for Unix-98 &c.
+AC_SYS_LARGEFILE
+
+if test "${with_sound}" != "no"; then
+ # Sound support for GNU/Linux and the free BSDs.
+ AC_CHECK_HEADERS(machine/soundcard.h sys/soundcard.h soundcard.h)
+ # Emulation library used on NetBSD.
+ AC_CHECK_LIB(ossaudio, _oss_ioctl, LIBSOUND=-lossaudio, LIBSOUND=)
+ AC_SUBST(LIBSOUND)
+fi