Makefile change to restart bootstraps

[Alexandre Oliva]

On Nov 14, 2000, kenner@vlsi1.ultra.nyu.edu (Richard Kenner) wrote:

>     They used to get quite frustrated when `make bootstrap' re-started the
>     build pretty much from scratch, and it would be quite annoying to have
>     the bootstrap restarted just because you tweak something in a config.h
>     file.

> But remember that machines are much faster than when people "used to"
> compain!

Not really.  One of the main problems with having `make bootstrap'
restarting from scratch is that, contrary to most people's
expectations, you won't get the same error you got previously.  Worse
yet: if you're using a compiler other than GCC as the bootstrap
compiler, and the previous build had already got past stage1, it's
very common that linking will fail because the bootstrap compiler
can't understand object files produced by the stage1 gcc, or because
it won't link with libgcc to get whatever auxiliary functions stage1
gcc depends on.

> The bootstrap shouldn't *need* to be "restarted". I'd argue
> quite the opposite: if a bootstrap failed for some reason, it's
> necessary to understand why and fix it so that it can run completely
> through.

So, the only way to do it safely is to have `bootstrap' depend on
`clean'.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me