what should bootstrap *really* do?

[Richard Earnshaw]

dj@redhat.com said:
> As for developers, it seems they fall into two categories: those who
> want bootstraps to be restartable, and those who don't.  The ones who
> don't can simply run "make clean" or "rm *.o" (which they'd have to do
> with the old bootstrap too), and the ones who do need lots of help
> from the Makefile. 

Since we seem to be gathering opinions....

What *I* want to do (when I'm tracking down a problem).  Is the equivalent 
of the following, which was possible with the old system.

Fix foo.c (eg combine.c):

# rebuild the bits of my compiler that have changed
make bootstrap3

# test my change -- if it works, do a full bootstrap.

Yes, I know that the compare will fail, but at this point I don't care.  I 
want to see first that it has fixed the problem I was working on.

I don't want to wait 6+ hours for a full bootstrap.  I don't want to start 
faffing with stamp files (that's error prone) and I don't want two builds, 
one made with bootstrap and one with plain make -- that just wastes disk 
space.

I could do all of those things with the old build system.  I can't do them 
with the new one.

About the only rule that I might have added to the old system was "make 
unstageX" (X=1,2,3...), which would effectively reverse the effect of 
"make stageX".

R.