zfs/config/always-no-unused-but-set-va...

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dnl #
dnl # Check if gcc supports -Wno-unused-but-set-variable option.
dnl #
dnl # We actually invoke gcc with the -Wunused-but-set-variable option
dnl # and infer the 'no-' version does or doesn't exist based upon
dnl # the results. This is required because when checking any of
dnl # no- prefixed options gcc always returns success.
dnl #
AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_NO_UNUSED_BUT_SET_VARIABLE], [
AC_MSG_CHECKING([for -Wno-unused-but-set-variable support])
saved_flags="$CFLAGS"
CFLAGS="$CFLAGS -Wunused-but-set-variable"
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
[
NO_UNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
AC_MSG_RESULT([yes])
],
[
NO_UNUSED_BUT_SET_VARIABLE=
AC_MSG_RESULT([no])
])
CFLAGS="$saved_flags"
AC_SUBST([NO_UNUSED_BUT_SET_VARIABLE])
])