[Mpi-forum] Preprocessor Constants

N.M. Maclaren nmm1 at cam.ac.uk
Fri Nov 19 11:11:56 CST 2010

On Nov 19 2010, Hal Finkel wrote:
>> >User code may assume that mpi.h is unavailable to the preprocessor
>> >unless the preprocessor constant _MPI is defined prior to source-file
>> >processing.
>> With one reading of the C standard, that breaks conformance; with 
>> another, it is recommended practice.
>I'm not sure what you mean by "breaks conformance." ...

It's all about the interpretation of the word "reserved" - reserved for
use by whom?  Future standards?  Implementors (which means of the compiler)?
Or compiler extensions (which is what MPI is)?

I wouldn't worry too much about it, in this case, but it IS worth being
careful in general.  It has caused trouble.

Nick Maclaren.

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