need finer-grained "C" header scheme information

[Phil Edwards]

On Wed, Jun 19, 2002 at 01:44:58PM -0700, Benjamin Kosnik wrote:
> something like:
> 
> # defaults
> c_headers_used = c_std
> c_compatibility_headers_used = no
> 
> # per-target-overrides
> switch $target_os in
>          qnx6.[1,2])
>            c_headers_used = c
>            c_compatibility_headers_used = no
> 	newlib-based-crosses)
>           c_headers_used = c
>           c_compatibility_headers_used = yes
> 
> ??

That would work.

Can we generalize "newlib-based-crosses" into something like

    # defaults
    if test x$with_newlib = xyes; then
        c_headers_used = c
        c_compatibility_headers_used = yes
    else
        c_headers_used = c_std
        c_compatibility_headers_used = no
    fi

    switch $target_os ....

or do they need to be all broken out in the target_os switch?

(Once this settles, we need to remember to go back and add documentation
for the new variables to configure.target and porting.texi.)

> Is it always assumed that configure.target bits are active before
> acinclude.m bits are used?

Yes; configure.target is sourced in GLIBCPP_CONFIGURE, which happens
early in configure.in.  GLIBCPP_ENABLE_CHEADERS happens about a dozen
lines further down.

Phil

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