dnl AC_VALIDATE_CACHE_SYSTEM_TYPE[(cmd)]
dnl if the cache file is inconsistent with the current host,
dnl target and build system types, execute CMD or print a default
dnl error message.
AC_DEFUN(AC_VALIDATE_CACHE_SYSTEM_TYPE, [
    AC_REQUIRE([AC_CANONICAL_SYSTEM])
    AC_MSG_CHECKING([config.cache system type])
    if { test x"${ac_cv_host_system_type+set}" = x"set" &&
         test x"$ac_cv_host_system_type" != x"$host"; } ||
       { test x"${ac_cv_build_system_type+set}" = x"set" &&
         test x"$ac_cv_build_system_type" != x"$build"; } ||
       { test x"${ac_cv_target_system_type+set}" = x"set" &&
         test x"$ac_cv_target_system_type" != x"$target"; }; then
	AC_MSG_RESULT([different])
	ifelse($#, 1, [$1],
		[AC_MSG_ERROR(["you must remove config.cache and restart configure"])])
    else
	AC_MSG_RESULT([same])
    fi
    ac_cv_host_system_type="$host"
    ac_cv_build_system_type="$build"
    ac_cv_target_system_type="$target"
])


dnl test whether dirent has a d_off member
AC_DEFUN(AC_DIRENT_D_OFF,
[AC_CACHE_CHECK([for d_off in dirent], ac_cv_dirent_d_off,
[AC_TRY_COMPILE([
#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>], [struct dirent d; d.d_off;],
ac_cv_dirent_d_off=yes, ac_cv_dirent_d_off=no)])
if test $ac_cv_dirent_d_off = yes; then
  AC_DEFINE(HAVE_DIRENT_D_OFF)
fi
])


dnl AC_PROG_CC_FLAG(flag)
AC_DEFUN(AC_PROG_CC_FLAG,
[AC_CACHE_CHECK(whether ${CC-cc} accepts -$1, ac_cv_prog_cc_$1,
[echo 'void f(){}' > conftest.c
if test -z "`${CC-cc} -$1 -c conftest.c 2>&1`"; then
  ac_cv_prog_cc_$1=yes
else
  ac_cv_prog_cc_$1=no
fi
rm -f conftest*
])])

dnl see if a declaration exists for a function or variable
dnl defines HAVE_function_DECL if it exists
dnl AC_HAVE_DECL(var, includes)
AC_DEFUN(AC_HAVE_DECL,
[
 AC_CACHE_CHECK([for $1 declaration],ac_cv_have_$1_decl,[
    AC_TRY_COMPILE([$2],[int i = (int)$1],
        ac_cv_have_$1_decl=yes,ac_cv_have_$1_decl=no)])
 if test x"$ac_cv_have_$1_decl" = x"yes"; then
    AC_DEFINE([HAVE_]translit([$1], [a-z], [A-Z])[_DECL])
 fi
])


dnl check for a function in a library, but don't
dnl keep adding the same library to the LIBS variable.
dnl AC_LIBTESTFUNC(lib,func)
AC_DEFUN(AC_LIBTESTFUNC,
[case "$LIBS" in
  *-l$1*) AC_CHECK_FUNCS($2) ;;
  *) AC_CHECK_LIB($1, $2) 
     AC_CHECK_FUNCS($2)
  ;;
  esac
])

dnl Define an AC_DEFINE with ifndef guard.
dnl AC_N_DEFINE(VARIABLE [, VALUE])
define(AC_N_DEFINE,
[cat >> confdefs.h <<\EOF
[#ifndef] $1
[#define] $1 ifelse($#, 2, [$2], $#, 3, [$2], 1)
[#endif]
EOF
])

dnl Add an #include
dnl AC_ADD_INCLUDE(VARIABLE)
define(AC_ADD_INCLUDE,
[cat >> confdefs.h <<\EOF
[#include] $1
EOF
])

dnl Copied from libtool.m4
AC_DEFUN(AC_PROG_LD_GNU,
[AC_CACHE_CHECK([if the linker ($LD) is GNU ld], ac_cv_prog_gnu_ld,
[# I'd rather use --version here, but apparently some GNU ld's only accept -v.
if $LD -v 2>&1 </dev/null | egrep '(GNU|with BFD)' 1>&5; then
  ac_cv_prog_gnu_ld=yes
else
  ac_cv_prog_gnu_ld=no
fi])
])