On 10/31/12 1:57 PM, "Dmitri Gribenko" <griboz...@gmail.com> wrote:
>On Wed, Oct 31, 2012 at 9:51 PM, Barrett, Brian W <bwba...@sandia.gov> >wrote: >> On 10/31/12 1:39 PM, "Paul Hargrove" <phhargr...@lbl.gov> wrote: >> >>>No, I don't have specific usage cases that concern me. >>> >>> >>>As I said a minute or two ago in a reply to Ralph, my concern is that >>>the >>>Sandia codes provide an "existence proof" that "really smart people" can >>>write questionable code at times. So, I fear that a >>>larger-than-expected >>>fraction of real codes would generate warnings. >> >> Not surprisingly, most of the codes I'm concerned about are really old >> (like pre-MPI old). The authors were dealing with more than one >> communication library, so they wrote wrappers inside their code for >> communication. The wrappers were for a bunch of different communication >> interfaces and so fairly agnostic, but looked a lot like MPI (because >>MPI >> looks a lot like NX, PVM, etc.). Anyway, they squashed down everything >>to >> either a void* or char* (remember, this is when void* was not always >> supported), passed that to MPI with a datatype, and off we go. > >Thank you for sharing the context. > >> That said, if we didn't throw a warning if the pointer is of type void* >>or >> char*, I think I'd be mostly ok with the patch being on by default. I'm >> not sure if that's possible or not... > >It is certainly possible to do that. However, we would lose the >ability to diagnose type mismatches for MPI_CHARACTER, but it is a >rarely-used type tag (is it?). My experience is that MPI_CHAR / MPI_CHARACTER are frequently used when MPI_BYTE should be used. So this is yet another mismatch that it's probably not a bad idea to complain too much about :). Brian -- Brian W. Barrett Dept. 1423: Scalable System Software Sandia National Laboratories
