• Nick Treleaven (16/16) Dec 16 2022 This code segfaults when the GC calls the dtor after the unittest
• Nick Treleaven (5/8) Dec 16 2022 This seems to work:
• ag0aep6g (6/12) Dec 19 2022 A quick test suggests that the context pointer is the last item in
• Nick Treleaven (5/19) Dec 23 2022 Great, thanks. The struct tupleof docs just link to the class
• Steven Schveighoffer (7/23) Dec 23 2022 Check if the struct is the init value?

Nick Treleaven <nick geany.org> writes:

This code segfaults when the GC calls the dtor after the unittest 
succeeds:

```d
unittest
{
     int i;
     struct S
     {
         ~this() { i++; }
     }
     (*new S).destroy;
}
```

It seems destroy clears the context pointer. Is there a way to 
test if the context pointer is null in the dtor, to prevent the 
increment?

Nick Treleaven <nick geany.org> writes:

On Friday, 16 December 2022 at 12:17:40 UTC, Nick Treleaven wrote:
 It seems destroy clears the context pointer. Is there a way to 
 test if the context pointer is null in the dtor, to prevent the 
 increment?

This seems to work:

         ~this()  trusted { if (&i > cast(void*)1024) i++; }

It would be better if there was a struct property to get the 
context pointer though.

ag0aep6g <anonymous example.com> writes:

On 16.12.22 14:07, Nick Treleaven wrote:
 This seems to work:
 
          ~this()  trusted { if (&i > cast(void*)1024) i++; }
 
 It would be better if there was a struct property to get the context 
 pointer though.

A quick test suggests that the context pointer is the last item in 
`tupleof`. So this might do the trick:

     ~this() { if (this.tupleof[$ - 1] !is null) i++; }

I don't know if it's guaranteed to work though. Might be an 
implementation detail.

Nick Treleaven <nick geany.org> writes:

On Tuesday, 20 December 2022 at 06:31:09 UTC, ag0aep6g wrote:
 On 16.12.22 14:07, Nick Treleaven wrote:
 This seems to work:
 
          ~this()  trusted { if (&i > cast(void*)1024) i++; }
 
 It would be better if there was a struct property to get the 
 context pointer though.

 A quick test suggests that the context pointer is the last item 
 in `tupleof`. So this might do the trick:

     ~this() { if (this.tupleof[$ - 1] !is null) i++; }

 I don't know if it's guaranteed to work though. Might be an 
 implementation detail.

Great, thanks. The struct tupleof docs just link to the class 
tupleof docs, which say:

 The order of the fields in the tuple matches the order in which 
 the fields are declared.

So I think for a struct the context pointer has to come after any 
fields.

Steven Schveighoffer <schveiguy gmail.com> writes:

On 12/16/22 7:17 AM, Nick Treleaven wrote:
 This code segfaults when the GC calls the dtor after the unittest succeeds:
 
 ```d
 unittest
 {
      int i;
      struct S
      {
          ~this() { i++; }
      }
      (*new S).destroy;
 }
 ```
 
 It seems destroy clears the context pointer. Is there a way to test if 
 the context pointer is null in the dtor, to prevent the increment?

Check if the struct is the init value?

```d
~this() { if(this !is this.init) ++i;}
```

Not ideal I guess, because really it's the context pointer you care about.

-Steve