On Sat, Mar 6, 2010 at 12:49 PM, Eric Blake <ebb9@xxxxxxx> wrote: > According to NightStrike on 3/6/2010 10:23 AM: >> It comes up often that we want to test to see whether a feature of GCC >> works. For instance, we want to see if -m64 is a valid gcc option to >> know if we should build the 64-bit libraries by default. Other things >> include checking for unicode support, and the -municode option. To do >> this, we usually do something like the following: >> >> _save_CFLAGS="$CFLAGS" > > Overkill. Shell assignments are NOT subject to word splitting, so it > _does not matter_ whether $CFLAGS contains spaces. It is perfectly safe > to use: > > _save_CFLAGS=$CFLAGS Well that just blew my mind. Well met! >> CFLAGS="$CFLAGS option" > > This line does indeed need double quotes, but that is in order to include > literal whitespace as part of the word that will later be interpreted as a > shell assignment. It is also possible (although less common) to write > this as: > > CFLAGS=$CFLAGS\ option > > with no change in semantics. > >> AC_COMPILE_IFELSE([AC_LANG_PROGRAM....... >> CFLAGS="$_save_CFLAGS" >> >> I was trying to improve upon that using AS_VAR_COPY for the >> save/restore, but I can't figure out how to handle variables >> containing spaces. > > They are handled like any other variable. > > AS_VAR_COPY([_save_CFLAGS], [CFLAGS]) Well, I didn't know the first part :( So with your guidance, I now have this: AC_DEFUN([MW64_VAR_PUSHPOP],[ AS_VAR_PUSHDEF([savevar],[_save_$1]) AS_VAR_COPY([savevar],[$1]) AS_VAR_APPEND([savevar],[" $2"]) $3 AS_VAR_COPY([$1],[savevar]) AS_VAR_POPDEF([savevar])]) Is this considered a clean way of doing things? _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx http://lists.gnu.org/mailman/listinfo/autoconf
