[RFC] adding a variable to .mk and Makefile.inc1 to point to top of the FreeBSD source tree

[Simon J. Gerraty]

On Tue, 7 May 2013 21:25:37 -0600, Warner Losh writes:
>where does MAKEOBJDIRPREFIX come into play?

I don't normally use it, it is a handy but rather crude implement.
I normally use 

MAKEOBJDIR='${.CURDIR:S,${SRCTOP},${OBJTOP},}'

which gives you a similar - but much neater result than
MAKEOBJDIRPREFIX.

>We do it both ways: on some architectures we have multiple =
>MACHINE_ARCHes per MACHINE (like mips and arm) and on others we have one =
>MACHINE_ARCH and mutliple machines (like i386 and pc98).

Yes, which is why I'm adjusting accordingly.

>We currently use ${MACHINE}.${MACHINE_ARCH} for cross builds, which =
>works out nicely. For historical reasons that turn out to be =
>inconvenient, we don't do this for native builds.

>Why is this gratuitously different than the current scheme? 

Do you mean why not simply use ${MACHINE}.${MACHINE_ARCH} always?
Encoding both MACHINE and MACHINE_ARCH always is doable, but I avoid '.'
because it prevents being able to  use modifiers like :R and :E
to separate the directory component from the target machine spec.

The projects/bmake branch is about showing how freebsd can be built in
meta mode.  The tree dependencies are represented as dir.target_spec

>would I build a pc98 build with this? And why have it be different for =

it would just get pc98 since there's no ambiguity.
But as noted above, if you wanted to always be explicit that wouldn't be
a problem (assuming '.' is avoided).