config/always-no-unused-but-set-variable.m4

   1 dnl #
   2 dnl # Check if gcc supports -Wno-unused-but-set-variable option.
   3 dnl #
   4 dnl # We actually invoke gcc with the -Wunused-but-set-variable option
   5 dnl # and infer the 'no-' version does or doesn't exist based upon
   6 dnl # the results.  This is required because when checking any of
   7 dnl # no- prefixed options gcc always returns success.
   8 dnl #
   9 AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_NO_UNUSED_BUT_SET_VARIABLE], [
  10         AC_MSG_CHECKING([for -Wno-unused-but-set-variable support])
  11
  12         saved_flags="$CFLAGS"
  13         CFLAGS="$CFLAGS -Wunused-but-set-variable"
  14
  15         AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
  16         [
  17                 NO_UNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
  18                 AC_MSG_RESULT([yes])
  19         ],
  20         [
  21                 NO_UNUSED_BUT_SET_VARIABLE=
  22                 AC_MSG_RESULT([no])
  23         ])
  24
  25         CFLAGS="$saved_flags"
  26         AC_SUBST([NO_UNUSED_BUT_SET_VARIABLE])
  27 ])