bug#7766: (lack of) config.h description in manual

[Karl Berry]

Hi Ralf and all,

A new GNU maintainer just asked me about how to use $(pkgdatadir) from
his C program.  I looked at the Automake manual and didn't see anywhere
especially good to point him at :(.  A couple thoughts I had as a result
of looking at this for him:

First, tiny English point in node Optional:
< As for `AC_CONFIG_FILES' (*note Requirements::), parts of the
> As with ...

The main point: although "amhello Explained" talks about
AC_CONFIG_HEADERS and gives a partial example, I don't see any "real"
description of how to determine what ends up in config.h and what the
#define names are.  If I'm not just missing something, I suggest a new
node, perhaps under "Generalities", which talks about Automake/C
linkage, including autoheader, etc.

The apparent reference definition for AC_CONFIG_HEADERS (in node
"Optional") says nothing about what it really does.

It belatedly occurs to me that perhaps this topic is gone into in more
detail in the Autoconf manual.  I don't have the energy to search
through it now, but if that is so, at least a cross-reference to that
would be nice.  (FWIW, I looked at all occurrences of config\.h and
CONFIG_HEADERS in the automake manual.)


Subsidiary points: in the general index (I continue to very strongly
encourage you to merge all indexes, BTW), I didn't find anything useful
for "preprocessor", or "#define", or "config.h", or anything else I
could think of.  Fortran preprocessing was the only thing.

Finally, the "amhello explained" node is pretty long.  It seems to break
up naturally into three pieces, for each of the files being explained.
Perhaps it would be good to make them each separate (sub)nodes.


Of course, all the above are just some ideas, please do whatever makes
sense and forget the rest.

Happy hacking in 2011,
karl