• Nick Treleaven (20/20) Feb 20 2015 Hi,
• Steven Schveighoffer (8/29) Feb 20 2015 I'm beginning to think this is the right thing to do. It confuses so
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (7/16) Feb 20 2015 And templated containers...

Nick Treleaven <ntrel-pub mybtinternet.com> writes:

Hi,

The following code is supposed to destroy the struct instance:

     import std.stdio;
     struct S{
         ~this(){"destruct".writeln;}
         }
     auto p = new S;
     destroy(p);
     "end".writeln;

It works correctly if I use destroy(*p), but the above code could 
perhaps be statically rejected by object.destroy to help prevent bugs. 
Currently, the pointer p is set to null without calling the destructor 
(with recent dmd the destructor is called, but only after "end" is printed).

Here is the destroy overload:

void destroy(T)(ref T obj)
     if (!is(T == struct) && !is(T == interface) && !is(T == class) && 
!_isStaticArray!T)
{
     obj = T.init;
}

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 2/20/15 1:05 PM, Nick Treleaven wrote:
 Hi,

 The following code is supposed to destroy the struct instance:

      import std.stdio;
      struct S{
          ~this(){"destruct".writeln;}
          }
      auto p = new S;
      destroy(p);
      "end".writeln;

 It works correctly if I use destroy(*p), but the above code could
 perhaps be statically rejected by object.destroy to help prevent bugs.
 Currently, the pointer p is set to null without calling the destructor
 (with recent dmd the destructor is called, but only after "end" is
 printed).

 Here is the destroy overload:

 void destroy(T)(ref T obj)
      if (!is(T == struct) && !is(T == interface) && !is(T == class) &&
 !_isStaticArray!T)
 {
      obj = T.init;
 }

I'm beginning to think this is the right thing to do. It confuses so 
many people, and setting a pointer/class reference/array to null is easy 
enough without needing a special function to do it. In other words, if 
you are using destroy, you aren't just trying to nullify a pointer. You 
want to destroy what the pointer represents.

The only problem is, how does this affect existing code?

-Steve

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 02/20/2015 12:30 PM, Steven Schveighoffer wrote:

 On 2/20/15 1:05 PM, Nick Treleaven wrote:

 It works correctly if I use destroy(*p), but the above code could
 perhaps be statically rejected by object.destroy to help prevent bugs.


 I'm beginning to think this is the right thing to do. It confuses so
 many people, and setting a pointer/class reference/array to null is easy
 enough without needing a special function to do it. In other words, if
 you are using destroy, you aren't just trying to nullify a pointer. You
 want to destroy what the pointer represents.

 The only problem is, how does this affect existing code?

And templated containers...

Despite the issue, I favor the current behavior partly because I am used 
to it from C++: A pointer going out of scope does not delete what it 
points to. (It can't do that because the pointer does not know about the 
object's ownership.)

Ali