(j3.2006) (SC22WG5.3729) [ukfortran] Atomic stuff

[Jim Xia]

> Any vendor who allows those as extensions can do whatever they like with 

> atomic.


Fair.  If there weren't any customers requesting this, we wouldn't have 
supported it either.  Actually I wasn't worried about sequence statement 
because I think anyone applying atomic operations on storage associated 
entities is clearly out of his mind.

What I'm really concerned about are structure components.  For a sequence 
derived type, we don't do any padding and it becomes equivalent to a C 
struct in pack mode.  So its elements can easily be out of natural 
alignments.  I would expect this could be a fairly common implementation 
on sequence types (or a user defined type rather than an intrinsic type) 
way back before Fortran 90 came around.  Another potential problem is a 
derived type with BIND attribute.  If the companion C processor requires 
structures to be in packed mode, then the derived type in Fortran side 
will also be without any alignment.  That too will cause trouble for 
atomic operations.

It seems to me that we can fix this by putting a sentence in the 
description of argument ATOM in ATOMIC_DEFINE and ATOMIC_REF that it can 
not be a subobject of sequence type or a derived type with BIND attribute.

Cheers,

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://j3-fortran.org/pipermail/j3/attachments/20081203/200a8bd1/attachment.html