Re: Unbounded strings (Was: Java vs Ada 95 (Was Re: Once again, Ada absent from DoD SBIR solicitation))

[bobduff@world.std.com (Robert A Duff)]

In article <dewar.848758301@merv>, Robert Dewar <dewar@merv.cs.nyu.edu> wrote:
>And of course it is quite clear that two writes to the same file using
>Put_Line with a file argument are NOT covered by paragraph 3. So that's
>mightly curious:
>
>    Put_Line (Standard_Output, "xxxx");
>
>appearing in two tasks is not covered, and could be erroneous, but
>
>    Put_Line ("xxxx");
>
>is OK. That seems quite weird to me, ...

Agreed.  In my opinion, both of the above should be considered
erroneous.  I said that in another article, and I also admitted that the
RM doesn't clearly say so.  As you say, if one thinks the above should
work, then one needs to worry about the granularity of interleaving.

>... though I see how paragraph 3 could
>be read this way.

>Without paragraph 3, I have no idea why Bob Duff thinks that the language
>has anything to say about either of these cases.

I think you're confusing what I said with what somebody else said.  Two
simultaneous Put_Lines are erroneous if they are writing to the same
file, but not if they are writing to two different files.  At least, in
my opinion, that's the way it *should* be.  The glitch in the RM wording
is that for the Put_Line without any file argument, there's no variable
in sight -- even though we know that Put_Line("xxx") and
Put_Line(Current_Output, "xxx") ought to have identical semantics.  If I
weren't so lazy, I tried to dig up some wording that says so, and then
we would be OK -- I don't remember exactly how the no-arg version is
defined.

>But in this case (reference counts), people do not agree on what is
>friendly. So I think it is something the ARG should pin down.

Apparently.  I'm surprised that you think the unprotected reference
count implementation is reasonable.  (Unless of course the compiler
knows there aren't any tasks causing trouble.)

- Bob