m4/st_save_restore_var.m4

AC_DEFUN([st_SAVE_VAR], [dnl
AS_IF([test -n "${$1+set}"], [st_saved_$1="${$1}"; unset $1])
])

AC_DEFUN([st_RESTORE_VAR], [dnl
AS_IF([test -n "${st_saved_$1+set}"], [$1="${st_saved_$1}"; unset st_saved_$1])
])