http://d.puremagic.com/issues/show_bug.cgi?id=2497

           Summary: delete and null relationship needs more details
           Product: D
           Version: 2.021
          Platform: PC
               URL: http://www.digitalmars.com/d/2.0/expression.html#DeleteE
                    xpression
        OS/Version: Linux
            Status: NEW
          Keywords: spec
          Severity: normal
          Priority: P2
         Component: www.digitalmars.com
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: jlquinn@optonline.net


1)

A a = null;
delete a;

is this OK or not?

2)

void do(A b) { delete b; }
A a = new A;
do(a);
if (a is null) { writefln("yes"); }

does a get reset to null or not?


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http://d.puremagic.com/issues/show_bug.cgi?id=2497


smjg@iname.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |smjg@iname.com
         OS/Version|Linux                       |All




------- Comment #1 from smjg@iname.com  2008-12-06 18:22 -------
1. Good question.

2. No, because do has no access to variable a.  However, it were declared as ref, it would.

It does say
"The pointer, dynamic array, or reference is set to null  after the delete is
performed."

Notice the singular.


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http://d.puremagic.com/issues/show_bug.cgi?id=2497





------- Comment #2 from jlquinn@optonline.net  2008-12-06 18:49 -------
(In reply to comment #1)

> 2. No, because do has no access to variable a.  However, it were declared as ref, it would.

OK, this is what I thought.  What happens when you access a, then?  In Java you'd get an NPE.  no matter how you try to access the object.  Does it coredump or is there a defined behavior?


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http://d.puremagic.com/issues/show_bug.cgi?id=2497





------- Comment #3 from jarrett.billingsley@gmail.com  2008-12-06 19:00 -------
It's undefined.  Comparing to Java doesn't make much sense here, since the only way an object can go away in Java is if no references refer to it, so there's no way to have a reference to an object that has been collected.

delete is sort of a "power user" tool for when you _know_ that there are no other references to the object and want to help out the GC a bit, so it's going to have sharp edges.


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http://d.puremagic.com/issues/show_bug.cgi?id=2497





------- Comment #4 from jlquinn@optonline.net  2008-12-06 23:23 -------
(In reply to comment #3)
> It's undefined.  Comparing to Java doesn't make much sense here, since the only way an object can go away in Java is if no references refer to it, so there's no way to have a reference to an object that has been collected.

Fair enough.  It would be useful to note that accessing a deleted class through the reference is undefined.  Otherwise it might leave others guessing.


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http://d.puremagic.com/issues/show_bug.cgi?id=2497



--- Comment #5 from github-bugzilla@puremagic.com 2012-01-22 21:03:54 PST ---
Commit pushed to https://github.com/D-Programming-Language/d-programming-language.org

https://github.com/D-Programming-Language/d-programming-language.org/commit/59d36352183e14ea08c4e64853a6f20a7112a3d4 fix Issue 2497 - delete and null relationship needs more details

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


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