bug#7773: (lack of) config.h description in manual

[Ralf Wildenhues]

Hello Karl, Eric,

* Eric Blake wrote on Tue, Jan 04, 2011 at 01:33:42AM CET:
> On 01/03/2011 05:00 PM, Karl Berry wrote:
> > Thanks for the reference.  Now that I know it, I suggest the Automake
> > manual simply have a sentence with an xref to that node.

Yes, I agree with that, and I am still going to do that.  You opened two
bug reports originally (inadvertently), I only closed the one that was
dealt with.  Sorry if that was unclear before.

> > Hmm, I'm not so sure that the GCS forbids doing the right thing (or that
> > it has to stay that way even if it does), but I won't pursue it further.
> 
> What the GCS requires is that you can do 'make prefix=/alternate/path'
> and have that propagate through all the directory variables.  Anything
> learned at configure time can thus be rewritten at make time, so the
> only safe place to record a directory variable's value is at make time.
>  I don't think this aspect of the GCS needs changing.
> 
> One other thing to point out is that the GCS documents that 'make
> install' should ideally not rebuild any source code, but that this ideal
> is only possible if you either _don't_ use 'make prefix=...', or if you
> use the same prefix in both 'make prefix=...' and 'make install prefix=...'.

I don't think that is correct.  In fact, I think it is entirely intended
to be possible to use a different prefix= setting for the all and for
the install targets, and the latter should still not rebuild sources.
Sort of a poor-man's DESTDIR.  You can see the usefulness on MSYS and
DJGPP (where DESTDIR does not work due to drive prefix concatenation).
(Of course Libtool doesn't support the non-DESTDIR way, but that's
another story ...)

Cheers,
Ralf