On 3/13/08, Ralf Wildenhues <Ralf.Wildenhues@xxxxxx> wrote: > * NightStrike wrote on Thu, Mar 13, 2008 at 10:07:31PM CET: > > On 3/13/08, Ralf Wildenhues <Ralf.Wildenhues@xxxxxx> wrote: > > > > > > AC_INIT > > > AC_DEFUN([FOO], [echo foo]) > > > AC_DEFUN([BAR], [AC_REQUIRE([FOO]) > > > echo bar]) > > > x=zork > > > AS_CASE([$x], [y*], [BAR]) > > > > > > will print 'foo' because FOO will be expanded outside of the AS_CASE. > > > I'm trying to follow this logic, but I'm not putting it together in my > > head. Why isn't the result nothing? > > Because it expands to this: > > x=zork > echo foo > case $x in > y*) > echo bar > ;; > esac > > That is, required macros of macro expansions that happen inside > defun'ed macros get pushed right before the outermost defun'ed macro. > <http://www.gnu.org/software/autoconf/manual/html_node/Dependencies-Between-Macros.html> > > Here's a slightly more useful example: > > # FIND(PATTERN, FILE) > # ------------------- > AC_DEFUN([FIND], > [AC_REQUIRE([AC_PROG_GREP]) > $GREP $1 $2 > ]) > > AS_CASE([$whatever], > [blabla], [FIND([pattern], [file])]) > FIND([pattern2], [file2]) > > > The AC_PROG_GREP will be expanded only once (that's what AC_REQUIRE > does). If it were expanded inside the case..esac, then if $whatever > did not match, the second FIND would provoke a syntax error because > $GREP has not been initialized at that point. > > One should not that this also frequently leads to confusion, because > users don't realize AC_REQUIRE'd macros end up quite a bit earlier than > they expect. Ok, now I understand. This is quite an interesting situation. I am guessing that this is why tools like autoscan or autoupdate will use actual case/if statements instead of the AS_CASE/IF macros. The bottom line is that if I stay away from AC_REQUIRE inside of these macros, there shouldn't ever be a problem, yes? _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx http://lists.gnu.org/mailman/listinfo/autoconf
