Re: Building for more than one host architecture

[npr@mpia-hd.mpg.de (Nick Rees)]

Tony Carter sent me a response which he accidently didn't send to the
exploder. It is appended (at his request) with my comments...

> From CARTER@AESIR.MIT.EDU Tue Jun  6 21:59 MET 1995
> Date: Tue, 6 Jun 1995 16:00:29 -0400 (EDT)
> From: "Tony Carter, MIT Bates Linac" <CARTER@AESIR.MIT.EDU>
> To: npr@mpia-hd.mpg.de
> Subject: Re: Building for more than one host architecture
> 
> Nick Rees writes:
> >
> >    (present workaround deleted)
> >
> >I think the ideal is to have a script in base/tools called HostArch
> >which returns the correct value of HOST_ARCH for the architecture you
> >are running on. Then, in CONFIG_SITE you define
> >
> >HOST_ARCH = $(shell HostArch)
> >
> >and it always works. The following should work (but has not been
> >checked on all architectures) for the current list of supported
> >hosts, but it would have to be adapted for new architectures:
> >  .
> >  .
> >  .
> 
> I like this, it is a clean approach.  However, it leaves some smaller issues
> unresolved.  In my case (and in yours) other variables should be different
> for each architecture.  For instance the line:
> 
> 	BUILD_ARCHS=$(HOST_ARCH) mv167
> 
> would be OK for the SPARC but would bomb on the Alpha since I don't have
> VxWorks on it.  This is a minor problem since it will only start to fail
> after the host arch is built.  But there may be more problematic cases.
> 
> If I take William Lupton's suggestion of having HOST_ARCH point to some
> local file that is specific to the architecture I'm building for and 
> generalize it a little more, I can have CONFIG_SITE be a soft link to
> a local file that is appropriate to the build I need to do.  This is not
> a general solution but it may work for now.
> 
> I am not that familiar with the options you have with gnumake.  Is it
> possible to use conditional statements to break CONFIG_SITE into pieces
> based on the value of HOST_ARCH?  We could then set the variables to the
> values appropriate to each host arch, or some similar approach.
> 
> Tony
>
 
I thought the answer to your point was to move any host dependent
definitions from CONFIG_SITE to CONFIG_SITE.Unix.<arch> (i.e the host
dependent file already exists, and I wouldn't like creating a new
one. It is also global so can be under the same CVS control).

So, in your case, in CONFIG_SITE you would put:

HOST_ARCH = $(shell HostArch)

and possibly (but not necessarily - it could be omitted) a default of

BUILD_ARCH = $(HOST_ARCH)

However, in CONFIG_SITE.Unix.sun4 (or whatever), you would put:

BUILD_ARCH = $(HOST_ARCH) mv167...

or, more perversely, (i.e. I am not sure whether it will work), if you
only wanted to build the IOC tools on this host architecture.

BUILD_ARCH = mv167.

This would override any definition in CONFIG_SITE, because
CONFIG_SITE.Unix.<arch> is processed after CONFIG_SITE but before
RULES_ARCHS, which is the only place it is used.

As to the HostArch script, can Janet (if you read this) take this as a
formal request to have this suggestion incorporated into the next
release. At least two people have voted for it...

Nick