[TUHS] 2.11BSD cross compiling update

[Dan Cross]

On Fri, Jan 13, 2017 at 12:57 PM, Nick Downing <downing.nick at gmail.com>
wrote:

> [snip]
>
> So what I ended up doing was to port a tiny subset of 2.11BSD libc to
> Linux, including its types. I copied the ctime.c module and prefixed
> everything with "cross_" so there was "cross_time_t" and so forth, and
> "#include <time.h>" became "#include <cross/time.h>", in turn this
> depends on "#include <cross/sys/types.h>" and so on. That way, the
> original logic worked unchanged.
>
> I decided to also redo the cross compilation tools (as, cc, ld, nm,
> ranlib and so on) using the same approach, since it was conceptually
> elegant. This involved making e.g. "cross_off_t" and "struct
> cross_exec" available by "#include <cross/a.out.h>", and obviously the
> scheme extends to whatever libc functions we want to use. In
> particular we use floating point, and I plan to make a "cross_atof()"
> for the C compiler's PDP-11-formatted floating-point constant
> handling, etc. (This side of things, like the cross tools, was
> working, but was not terribly elegant before).
>
> So then I got to thinking, actually this is an incredibly powerful
> approach. [snip]
>

That sounds incredibly tedious. Can you specify a compiler flag to disable
searching the host /usr/include? Then you could set your own include path
and not have conflicts with headers from the host system. With, say, GCC
one could use `-ffreestanding` or `-nostdinc` and the like.

        - Dan C.
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