Idea: Splitting up config header

[Gabriel Dos Reis]

Phil Edwards <phil@jaj.com> writes:

| As we add AC_DEFINEs to the configury, 'autoheader' makes certain that
| we add the needed lines to config.h.in.  The current config.h.in contains
| HAVE_foo's for multiple possibilities, all jumbled together:
| 
|     1) header macros used only while building libstdc++
|     2) header macros used only while using libstdc++
|     3) header macros used while both building and using libstdc++
|     4) header macros used only while testing libstdc++
|     5) header macros never used
| 
| (1) through (3) are entangled -- think "Gordian Knot" -- and I've no plans
| to try and fix that.

I do not consider that is broken, therefore I do not consider it needs
a "fix".

| I propose splitting (4) out into its own header.

That makes sense to me.

| I propose splitting (5) out into its own header.  If you're wondering,
| "why do we name macros in config.h.in which will never be used?" the answer
| is, we didn't, autoheader added them.  See, in addition to adding all the
| macros that we define ourselves, autoheader also adds macros which autoconf
| defines for us whether we {need,use,want} them or not.

what do they look like?


-- Gaby