Re: Understanding Multilibs ;-)

[Phil Edwards <phil at jaj dot com>]

On Sun, Jul 27, 2003 at 11:57:50PM -0400, Nathanael Nerode wrote:
> So, I decided to take a crack at moving multilibbing to the top level.

Give me another day or two to check in the v3 transition first?


> At first it looked simple: just call gcc --print-multi-lib.  
> Of course it couldn't be *that* simple.  ;-)
> 
> config-ml.in does various per-target per-'enable'-option pruning of the
> list before operating.  But in the code it puts into Makefiles, 'gcc 
> --print-multi-lib' is just used directly.  Hmm?

The only Makefiles touched are the post-pruning ones, so that the code
using --p-m-l directly is operating on a known-good subset of the original
computer multilib list.  Does that help?


> Well, in any case, what I want to do is this.
> * Get the list of lib versions and corresponding options.  
> (`gcc --print-multi-lib` if that's really sufficient).

Maybe the per-target-per-enable pruning could be moved up there as well?
Automake is about to import config-ml.in for their use, so it'd be nice
to get all the GCC-isms out.


> * Create a target subdir for each one (assuming 'a' and 'b' are the 
> lib variants)...
> i686-pc-linux/a/libstdc++-v3
> i686-pc-linux/a/libf2c
> i686-pc-linux/b/libstdc++-v3
> i686-pc-linux/b/libf2c
> etc...

Some questions at random:

What is 'a' in the standard/normal/primary/nothing-special case?

What are the names for combinations?  'ab'?

Can we do this in such a way to preserve this bit snagged from config-ml.in:

  # The build tree is layed out as
  #
  # ./
  #   newlib
  #   m68020/
  #          newlib
  #          m68881/
  #                 newlib
  #
  # The nice feature about this arrangement is that inter-library references
  # in the build tree work without having to care where you are.

I'm sure the answer is yes, I just wanted to throw that out there as a
talking point.


Phil

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