Re: [crosstool-NG] Design discussion

[Rob Landley <rob at landley dot net>]

On Wednesday 08 April 2009 04:14:25 Mark A. Miller wrote:
> On Mon, Apr 6, 2009 at 7:11 PM, Stefan Hallas Andersen
> I believe the discussion amounted to how a cross-compiler was built,
> not the red herring of, "Ignore cross-compiling entirely and do native
> compilation!" That is where they fork in totally different directions.
> But as for building cross-compilers, they're still quite related.

Actually, the discussion clarified for me that they're not as related as I 
thought.  The goals of the two projects are very different.

Crosstool-NG seems to be aimed at reverse engineering the specific cross 
compiler variants used to build existing binary root filesystems, so you can 
extend those root filesystems without replacing any of the existing binaries, 
or having to statically link your new additions.

For FWL, my only goal was "support reasonably efficient execution on this 
target hardware".  One of my design assumptions was that you were going to 
either build a fresh filesystem entirely from source, or statically link any 
additions to existing (subtly incompatible) filesystems.  This let me 
eliminate an awful lot of complexity which Yann has to face head on.

So with crosstool-NG, you can't really ask "what's the toolchain for PPC 440" 
because it's capable of producing over 100 of them _just_for_ppc_440_.  (4 
binutils versions, times 9 gcc versions, times 16 Linux versions, without 
even enabling the obsolete or experimental options.  Then there's whether to 
target Linux or bare metal, whether to use sjlj exceptions or dwarf2, and so 
on.)

My project assumes that "what's the toolchain for PPC 440" should have a 
simple answer, including a URL where you can download the prebuilt binary.

> I've mentioned it to Yann personally, but I'll state it on the list, I
> have no issue with him personally, and as for crosstool-ng, it's a
> package that he coded in his free time for other people, so criticisms
> can only go so far. (Why didn't you do X?!, et cetera). But I think
> his cross-compiler could be done better, and that's why he and Rob
> decided to have their discussion public.

Just about everything can be improved.  I think we've added enough items to 
his TODO list for one week. :)

> > Where this not supposed to be a crosstool-ng design discussion thread
> > instead of a >> who can write the longest emails competition << ?
>
> Yann asked Rob as to his opinions, and as opinions go, they're wordy.
> So are mine.

I sort of started it.  Yann emailed me in response to my March 7 blog entry, 
which was largely about my first reactions to crosstool-ng:

  http://landley.net/notes-2009.html#07-03-2009

He said he only catches up on my blog about once a month, so it took him a 
while to notice I'd mentioned his stuff.  We emailed back and forth a bit 
privately, and I suggested that we have the discussion on this list in case 
anybody else wanted to contribute to it or found it interesting.  (In 
retrospect, that part was apparently a mistake.)

I think the thread's pretty much wound down now...

Rob
-- 
GPLv3 is to GPLv2 what Attack of the Clones is to The Empire Strikes Back.

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