Thanks guys, I actually sent a "solution" much like yours Nick. Don't know why Stefano didn't send my answer. This is what I came up with: AC_DEFUN([TRICK], [m4_divert_text([HELP_CANON], [_ACEOF echo -en "\n* --option=VAL Date: `date`" cat <<\_ACEOF])]) TRICK You can see automake's archives for my whole message. Te code above will get hooked at the end of `HELP_CANON' (before the `heredoc' ends), or after the `Fine tuning' options if canonical support macros hasn't been called. Something that did surprise by looking at `general.m4' is that sections such as HELP_CANON, HELP_BEGIN, etc, have all been allocated sequentially, leaving no room for per-project customization. This is just my ignorant's opinion. I'm far from being a m4, autoconf, or automake specialist. Thanks, On 13/12/2012, Nick Bowler <nbowler@xxxxxxxxxxxxxxxx> wrote: > On 2012-12-13 10:20 -0700, Eric Blake wrote: >> On 12/13/2012 05:58 AM, Stefano Lattarini wrote: >> > On 12/11/2012 12:57 AM, Eduardo Costa wrote: >> >> Is it possible at all to have a configure option whose help message can >> >> expand a >> >> variable, or can otherwise accept the output of a command at >> >> configure-time? >> >> >> >> For example, imagine this as part of the output of `./configure': >> >> >> >> --with-user=user Who to complain to (default X) >> >> >> >> Where X could be, say, the output of the command `whoami'. >> >> >> >> This might be done by usual means (couldn't do it) or just with some >> >> trickery to to inject the string manually at the end of some section >> >> (say HELP_CANON or other), and giving the output of the command on a >> >> new line, so it doesn't get inside the `cat << LABEL ... LABEL' >> >> constructs that seem to be used to output options and help messages. >> >> Unfortunately, it looks like the current setup of autoconf is pretty >> hard-coded to constant strings determined at m4-time; making it use >> shell variables for dynamic output would require quite a bit of patching >> (maybe by introducing new macros such as AC_ARG_WITH_UNQUOTED, to take >> care of the tweaks needed to close the quoted heredoc, open an unquoted >> heredoc to do the substitution, then reopen the quoted heredoc for the >> rest of the script). It sounds like a useful request, though. > > FWIW it's not too hard to hack it: > > AC_ARG_WITH([user], [_ACEOF > # Eschew error handling! > me=`whoami` > cat <<EOF dnl > m4_newline([AS_HELP_STRING([--with-user], > [Who to complain to (default $me)])])dnl > m4_newline([EOF]) > cat <<\_ACEOF]) > > but that is, of course, relying on internal details of how Autoconf > generates the code to produce --help output. But there remain other > problems: firstly, the --help text appears quite early in the configure > output -- much earlier than the position of AC_ARG_WITH in configure.ac > would imply. This may make it hard to put anything useful in the help > text, without computing it directly in AC_ARG_WITH_UNQUOTED or whatever > (as done in the above example). > > Secondly, regarding this specific example, I don't know if whoami is > universally available. So determining the default username is probably > within the realm of a "full" configure test, with at least one invocation > of AC_CHECK_PROGS. Such a test is almost certainly too much to do before > printing --help output. > > Normally it is sufficient to just write the --help text as a static > string explaining how the default is determined. In the case of a > username like above, I would probably do something like: > > --with-user=user Who to complain to (default: current user) > > and then make the configure script print a line such as: > > Checking which user will receive complaints... nbowler > > Cheers, > -- > Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) > _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx https://lists.gnu.org/mailman/listinfo/autoconf
