(j3.2006) (SC22WG5.3587) OPTIONAL arguments and C interop

Jim Xia jimxia
Wed Jul 16 15:25:37 EDT 2008

j3-bounces at j3-fortran.org wrote on 07/16/2008 10:47:44 AM:

> a) Change the specification to require an extra argument that would 
> indicate whether an optional argument was present. This extra argument 
> would be hidden in the Fortran interface, but be explicit in the 
> corresponding C prototype.  (This matches that vendor's Fortran 
> convention.)
> b) Delete the capability of OPTIONAL arguments in BIND(C) interfaces 
> entirely.
> In the discussion so far, alternative (a) was viewed unfavorably for 
> multiple reasons. 

Choice (a) is in no way worse than the original design.  I don't 
understand why a statement like "alternative (a) was viewed unfavorably" 
can be made based on one vendor's implementation vs. another's.  How many 
Fortran vendors are there in the world at this point?

However, the choice between keeping the current 
> proposal and removing it (alternative b) was not fully discussed. 
> Neither were any other alternatives. 
> Editorial comments on alternative (b):  The discussion of OPTIONAL 
> arguments in the TR, and associated edits, are a very small fraction of 
> the text involved, so removing it is editorially easy. On the other 
> hand,  this feature was explicitly included in the original mandate for 
> the TR, so there should be a significant technical reason for change at 
> this point.

Not able to support OPTIOANL with VALUE attribute is a significant 
technical reason.


Jim Xia

RL Fortran Compiler Test
IBM Toronto Lab at 8200 Warden Ave, Markham, On, L6G 1C7
Phone (905) 413-3444  Tie-line 313-3444
email: jimxia at ca.ibm.com
D2/YF7/8200 /MKM
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