[mpich-discuss] Extensible Clang type annotation

[Jed Brown]

On Wed, Jan 2, 2013 at 1:23 PM, Dmitri Gribenko <gribozavr at gmail.com> wrote:

> Unfortunately we can not, because user-defined datatypes are
> syntactically different from builtin datatypes in MPICH.  MPI_INT is a
> macro, so what Clang sees is essentially a magic number.  With
> user-defined datatypes there's an identifier (MyEnumDatatype) that
> actually shows up in the AST.  There's a separate quirk in Clang for
> handling these magic numbers and corresponding 'static const'
> variables (not needed for OpenMPI, btw).
>

Okay, makes sense.


>  > so that the symbols are guaranteed to only show up once in
> > executables (rather than once per compilation unit)?
>
> A smart enough compiler (and Clang is smart enough) will eliminate
> those even at -O0.
>

Okay, gcc also removes them with optimization. Thanks, Dmitri.
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