Re: How can I enable option-checking from configure.ac after it being default-disabled?

[Hans-Peter Nilsson]

> From: Nick Bowler <address@hidden>
> Date: Mon, 19 Mar 2012 14:51:25 +0100

> On 2012-03-18 18:24 +0100, Hans-Peter Nilsson wrote:
> > Hi.  I don't see a way to turn on option-checking after it being
> > disabled-by-default due to AC_CONFIG_SUBDIRS.

> > have a look at its configure.ac), there's the hopefully
> > self-explanatory:
> > 
> > # The directory test/installtest isn't configured until after
> > # installation, but to make autoreconf update this directory we
> > # have to mention it here
> > if false; then
> >     AC_CONFIG_SUBDIRS([test/installtest])
> > fi
> 
> It is actually the call to AC_CONFIG_SUBDIRS which disables option
> checking.

Are you re-stating what I mentioned above or does it disable
option-checking in a different way than I mentioned?
(I realise that "call" here is AC_CONFIG_SUBDIRS being expanded,
not the resulting shell-code being executed.)

>  Since you're only doing this to make autoreconf recurse into
> the subdirectory, and don't actually care about the expansion of
> AC_CONFIG_SUBDIRS, you can fool autoreconf into thinking you called
> AC_CONFIG_SUBDIRS without actually doing so.
> 
> For example:
> 
>   dnl Fool autoreconf into thinking we called AC_CONFIG_SUBDIRS here by
>   dnl temporily suppressing its definition.
>   m4_pushdef([AC_CONFIG_SUBDIRS], [])
>   AC_CONFIG_SUBDIRS([test/installtest])
>   m4_popdef([AC_CONFIG_SUBDIRS])
> 
> This is (ab)using internal details of autoreconf, thus it might not be
> guaranteed to work in the future.

But is this considered a cleaner way than getting that effect
through the never-executed idiom I used above?

And more importantly, will your idiom have the desired effect:
not disable option-checking by default?  (The answer may be
obvious to you autoconfers.)

I forgot to mention the fun-and-anecdotal part: stating
--enable-debugging instead of --enable-debug (not looking at the
build-log) and wondering why the debugging info was so
optimized-out; mis-remembering that I should be getting errors
for unsupported configure-options because of observations
*before* adding the non-call to AC_CONFIG_SUBDIRS. :) (Now I've
"solved" this supposedly-common mistake by erroring out for
AC_ARG_ENABLE([debugging]).)

brgds, H-P