Re: Ada files now checked in

[Zack Weinberg <zack at codesourcery dot com>]

On Sat, Oct 06, 2001 at 01:07:45PM -0400, dewar@gnat.com wrote:
> <<That is the situation that the vast majority of users of the FSF CVS
> tree will find themselves in.  It is the one that we *must* ensure
> works, at least for all popular free operating system distributions.
> >>
> 
> We cannot necessarily ensure this works, because we don't know what 
> system integrators will provide. If they provide non-working versions
> of GNAT (e.g. the RPM's that were distributed for 3.13), then it may or
> may not be possible to bootstrap using them, and if it is not possible,
> then it may not be practical to correct this.
> 
> Most certainly in the long run, you cannot expect that a given version
> of the GNAT sources can be built by an arbitrarily older version of GNAT
> supplied by your "system integrator". 

You expressed this concern several times.  I should clarify what I
mean by "works".

"You need a newer version of GNAT, go here (URL)" is an acceptable
answer to a bootstrap problem caused by a bug in a vendor's supplied
version of GNAT.

"You need a version of GNAT packaged just so, go here (URL)" is not an
acceptable answer to a bootstrap problem caused by the Makefile not
being clever enough to find the appropriate compiler driver.

In other words, we obviously do not expect the bootstrap to work in
the presence of arbitrarily bad bugs in the bootstrap compiler.  We
*do* need to make our best effort to locate and use what the system
provides.

Also, the whole point of the bootstrap sequence is to insulate us from
bugs in the bootstrap compiler.  I am not familiar with the history of
GNAT, but I would hope that the same techniques used in the back end
would make it possible to build with buggy previous versions of GNAT.
That is, starting with no optimization, avoiding features known to be
buggy, etc.

zw