08-302

To:        J3-USTAG
From:      Van Snyder
Subject:   Storage_Size integration
Date: 2008 November 19
Reference: 08-207

In paper 08-207, J3-USTAG advocates to add STORAGE_SIZE to the list of
functions allowed by C1288 on page 310 in 08-007r2.

WG5 has decided to delete the constraint from Fortran 2008.

The intent of the constraint was to require that the stack frame of the
procedure be the same size for every iteration of the loop over array
elements, which would facilitate the optimization of moving the loop over
array elements inside the elemental procedure, that is, the specification
part need be elaborated only once.  Because Fortran 2003 introduced
deferred length components, it is, however, possible to cause a local
variable of the elemental procedure to be an automatic variable that has
a different size for each element of the actual argument array(s).

A processor can, however, move the creation of offending automatic
variables inside the loop over array elements, and the elaboration of the
remainder of the specification part outside the loop, by carrying out
exactly the same analysis as would be required to announce a violation of
the constraint.

The constraint is therefore not useful, and retaining it just makes the
standard longer and requires all processors to be able to diagnose
violations of it, even if they do not use the analysis required by it to
carry out the optimization.