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The levelstring FROMVAR is expanded and checked for verbal names that will map on to eight different levels - the VARNAME will receive this numeric level where "all" maps to 7 (lower three bits set) higher levels for 8 and 9 exist too. This macro is a nice helper to convert user input of a –with-opt=level into a numeric form that can be simply pushed as a #define like with AC_DEFINE:

   default YESLEVEL = 2 /* including unknown levelspec */
 default DEFAULT  = 0 /* when named level is empty */

The DEFAULT value is used if the NAMED levelstring has become empty and it is copied without further conversion - a default of "0" is used if absent - identical to "no". A "yes" will be set to the YESLEVEL - and note that "yes" has "2" as its default value not "1". (which comes from its original use to set a "gcc -O2").

the mnemonic names are:

  9| insane |ultrasome|experimentalplus
  8| ultra  |ultra|experimental)
  7| all    |muchmore|somemanymore|manymoreplus
  6| most   |manymore|most)
  5| strict |somemore|almost
  4| more   |more
  3| extra  |manyplus|plusmuch|somemany|plusmany
  2| many   |many|much|(yes)
  1| some   |some|plus

note that a level can be constructed of (some|plus) = bit-0, (many|much) = bit-1, (more) = bit-2, (ultra|experimental) = bit-3 at least in a left-to-right order, ie. plusmanymore=7

Example usage:

  test "$GCC" = "yes" && CFLAGS="$CFLAGS -O$OPTLEVEL)

Source Code

Download the latest version of ax_numeric_namedlevel.m4 or browse the macro’s revision history.


Copyright © 2008 Guido U. Draheim

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