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Subject: Re: [OMPI users] [EXTERNAL] Re: mpicc link shouldn't add -ldl and -lhwloc
From: Jed Brown (jed_at_[hidden])
Date: 2012-05-31 13:03:58

On Thu, May 31, 2012 at 6:20 AM, Jeff Squyres <jsquyres_at_[hidden]> wrote:

> On May 29, 2012, at 11:42 AM, Jed Brown wrote:
> > The pkg-config approach is to use pkg-config --static if you want to
> link that library statically.
> Do the OMPI pkg-config files not do this properly?

Looks right to me. I think the complaint was that there was no way to
specify the equivalent using wrapper compilers. I don't like the wrapper
compiler model (certainly not for languages with a common ABI like C), but
pkg-config doesn't have a good way to manage multiple configurations.

> > So the problem is almost exclusively one of binary compatibility. If an
> app or library is only linked to the interface libs, underlying system
> libraries can be upgraded to different soname without needing to relink the
> applications. For example, libhwloc could be upgraded to a different ABI,
> Open MPI rebuilt, and then the user application and intermediate MPI-based
> libraries would not need to be rebuilt. This is great for distributions and
> convenient if you work on projects with lots of dependencies.
> >
> > It's not such an issue for HPC applications because we tend to recompile
> a lot and don't need binary compatibility for many of the most common use
> cases. There is also the linker option -Wl,--as-needed that usually does
> what is desired.
> Mmmm. Ok. Brian and I are going to be in the same physical location next
> week; I'll chat with him about this.