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

[Paul Brook <paul at codesourcery dot com>]

On Monday 16 January 2006 17:10, Richard Kenner wrote:
>     I don't see how this is any different to boostrapping gcc with any
>     other system compiler. It's fairly common for the system compiler to
>     use a different ABI to the new gcc. Why is 32/64-bit any different?
>
> It isn't any different, which is the whole point.  The point is that
> what's being built is a compiler that's for a different host than we
> tell configure that it's for: specificially it's a cross-compiler and
> we're saying it's a native compiler.

I don't see why the requirement for a "native compiler" is anything stronger 
than "a binary that runs on this machine".

You seem to be suggesting that we shouldn't support 3-stage bootstrap with 
anything other than an identical version of gcc. I thought one of the main 
points of bootstrapping was that the stage1 compiler can be built by 
anything, as long as we can then run it to build a proper compiler.

If not what host triplets should I use for random HP, Sun and Apple system 
compilers?

> The issue isn't what compiler *builds* the stage1 compiler, but what the
> stage1 compiler *is*: if it's not for the same system as its target, it's
> not a native compiler, but a cross-compiler and it doesn't make sense to
> bootstrap cross-compiler (or, to be precise, if you do so, you need an
> additional stage, so that compiler would become a "stage0" compiler).

Only if you assume a "cross" compiler and a true native compiler generate 
different code. I certainly hope that isn't the case.

Paul