------- Comment #8 from John dot Harper at mcs dot vuw dot ac dot nz 2007-06-19 01:13 ------- Subject: Re: Pure function not allowed in specification expression
On Tue, 18 Jun 2007, pault at gcc dot gnu dot org wrote: > Date: 18 Jun 2007 22:49:37 -0000 > From: pault at gcc dot gnu dot org <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED] > Subject: [Bug fortran/32386] Pure function not allowed in specification > expression > > > > ------- Comment #7 from pault at gcc dot gnu dot org 2007-06-18 22:49 ------- > John, > > 5.1 > .....many snips..... > ....If a specification-expr involves a reference to a specification function > (7.1.6.2), the expression is considered to be a nonconstant expression. If the > data object being declared depends on the value of such a nonconstant > expression and is not a dummy argument, such an object is called an automatic > data object. > > I can see why you should think that this is OK. However, this section of the > standard says otherwise. In fact, there is a practical consideration, which > probably drives the standard: > > This character length cannot be computed at compilation time because the > specification function is needed. Automatic objects in procedures have their > variable properties calculated in the interface, which is not available for > the > main program. Thus, even were this legal code, I would not have the slightest > idea how to implement it. > > My vote is that this is invalid. I now agree the code was invalid - I had found 7.1.6.2 but overlooked 5.1 before sending the bug report. You may be amused to know that some compilers do implement that type of automatic data object: g95 and Sun f95. However Compaq f95 and NAG f95 disallow it. I don't think a bug report to g95 or Sun is warranted though: the part of 5.1 that the program violates is not in a Constraint. -- John Harper, School of Mathematics, Statistics and Computer Science, Victoria University, PO Box 600, Wellington 6140, New Zealand e-mail [EMAIL PROTECTED] phone (+64)(4)463 5341 fax (+64)(4)463 5045 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32386
