Status and rationale for toplevel bootstrap (was Re: Example of debugging GCC with toplevel bootstrap)

[Richard Kenner]

    We already do "sort of" bootstrap libada by including some rts routines 
    in the compiler.  

Right, because those are explicitly listed in the compiler's Makefile
and are part of the compiler.

    It would be possible to do so by really building libada three times,
    rather than by using parts of it both in the compiler and out of it.
    This is a cleanup, but would also allow comparison of the
    stage2/stage3 libada and expose possible miscompilations of the Ada
    front-end.

I don't follow.  We already see it if there's a miscompilation of the
Ada front end.

    This is not in my list of things to do, by the way, but it is plain 
    impossible with the old bootstrapping mechanism.

I see it as "impossible with the old bootstrapping mechanism" as being
for a good reason: it's not part of the compiler!  I still fail to understand
what it means to "bootstrap" anything other than a compiler: that word, to
me, talks only about compilers.

I still haven't heard any advantages of the new method, nor heard from 
anybody who's using it: most people I've seen who've weighed in on this
discussion say "it doesn't matter to be: I'm using --disable-bootstrap".

Can you say why this is a good thing? All I see are the disadvantages and
I think I'm far from the only one.