Re: Building for older systems

[Michael Eager <eager at eagerm dot com>]

On 12/01/2015 06:59 AM, Carlos O'Donell wrote:
> On 12/01/2015 09:56 AM, Michael Eager wrote:
> > On 11/29/2015 07:02 AM, Carlos O'Donell wrote:
> > > On 11/29/2015 09:20 AM, Michael Eager wrote:
> > > > Any solutions to building for an older glibc?
> > >
> > > There is only one supported way to do what you want.
> > >
> > > You need to build against an old sysroot e.g. --sysroot option
> > > in gcc. With the old system root installed in some path to allow
> > > you to compile against it.
> >
> > That is equivalent to building on a VM running an older Linux,
> > which is what I have been doing.
> >
> > There are dependencies in current tool chains for packages
> > (or versions) which are not available on old (or, in the case
> > of RH6.2, ancient) versions of Linux.
>
> How does this matter to you? The tools can have arbitrary dependencies,
> but it's the dependencies of the generated code that matters.

It matters that I'm not able to build a current tool chain on
an old system without installing a large number of new packages.
And these have other dependencies.

> As always, the compiler injects dependencies into the generated code
> at times and thus you must have a compatible compiler runtime also
> on the old legacy system.
>
> In practice you almost always need to build a toolchain of the same
> vintage as your legacy system and use that for cross-compiling to the
> target legacy system using a sysroot.
>
> All in all it's about the equivalent of VM, but in a cross-compilation
> environment. Any shortcuts you take will eventually come back to bite
> you.

I'll look at using sysroot.  It might address the build dependency
issues.


--
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077