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digitalmars.D.learn - Adding pointers to GC with destructers

reply "Freddy" <Hexagonalstar64 gmail.com> writes:
C libraries have a pattern of
----
HiddenType* getObj();
void freeObj(HiddenType*);
----
Is there any way I can make the GC search for a "HiddenType*" and 
run "freeObj" when the pointer is not found.
Apr 19 2015
next sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 04/19/2015 04:38 PM, Freddy wrote:

 C libraries have a pattern of
 ----
 HiddenType* getObj();
 void freeObj(HiddenType*);
 ----
 Is there any way I can make the GC search for a "HiddenType*" and run
 "freeObj" when the pointer is not found.


Not automatically. Check out addRange and addRoot:

   http://dlang.org/phobos/core_memory.html

Ali
Apr 19 2015
parent reply "Freddy" <Hexagonalstar64 gmail.com> writes:
On Monday, 20 April 2015 at 02:56:35 UTC, Ali Çehreli wrote:

 Not automatically. Check out addRange and addRoot:

   http://dlang.org/phobos/core_memory.html

 Ali


The destructor doesn't seem to be running
----
import std.stdio;
import std.c.stdlib;
import core.memory;
struct Test{
	~this(){
		writeln("free: ",&this);
		free(&this);
	}
}

void main(){
	auto ptr=cast(Test*)malloc(4);
	writeln("create: ",ptr);
	GC.addRange(ptr,0,typeid(Test));
	ptr=null;
	GC.collect();
}
----
$ rdmd test
create: 1EEC730
Apr 20 2015
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 04/20/2015 02:48 PM, Freddy wrote:

 On Monday, 20 April 2015 at 02:56:35 UTC, Ali Çehreli wrote:

 Not automatically. Check out addRange and addRoot:

   http://dlang.org/phobos/core_memory.html

 Ali


 The destructor doesn't seem to be running


Sorry, I misunderstood you. You can use a RAII object as ketmar said:

import std.stdio;
import std.c.stdlib;

struct Test{
     void* ptr;

     ~this(){
         writeln("free: ",&this);
         free(ptr);
     }
}

void main(){
     auto ptr=cast(Test*)malloc(4);
     writeln("create: ",ptr);

     auto test = Test(ptr);  // <-- The dtor of this object will free
}

Ali
Apr 20 2015
parent "Freddy" <Hexagonalstar64 gmail.com> writes:
On Monday, 20 April 2015 at 22:24:53 UTC, Ali Çehreli wrote:

 On 04/20/2015 02:48 PM, Freddy wrote:

 On Monday, 20 April 2015 at 02:56:35 UTC, Ali Çehreli wrote:

 Not automatically. Check out addRange and addRoot:

  http://dlang.org/phobos/core_memory.html

 Ali


 The destructor doesn't seem to be running


 Sorry, I misunderstood you. You can use a RAII object as ketmar 
 said:

 import std.stdio;
 import std.c.stdlib;

 struct Test{
     void* ptr;

     ~this(){
         writeln("free: ",&this);
         free(ptr);
     }
 }

 void main(){
     auto ptr=cast(Test*)malloc(4);
     writeln("create: ",ptr);

     auto test = Test(ptr);  // <-- The dtor of this object will 
 free
 }

 Ali


I believe your original understanding was right.I want to have 
HiddenType* be garbage collected and finalized(freed,destructed) 
when no more references to it are found(stack or heap). I could 
use reference counting but it seems inefficient for a program 
rarely collecting and constantly coping.
Apr 20 2015
prev sibling next sibling parent ketmar <ketmar ketmar.no-ip.org> writes:
On Sun, 19 Apr 2015 23:38:47 +0000, Freddy wrote:


 C libraries have a pattern of ----
 HiddenType* getObj();
 void freeObj(HiddenType*);
 ----
 Is there any way I can make the GC search for a "HiddenType*" and run
 "freeObj" when the pointer is not found.


wrap it in class/struct and run `freeObj()` in destructor.=
Apr 19 2015
prev sibling parent "Martin Nowak" <code dawg.eu> writes:
On Sunday, 19 April 2015 at 23:38:49 UTC, Freddy wrote:

 C libraries have a pattern of
 ----
 HiddenType* getObj();
 void freeObj(HiddenType*);
 ----
 Is there any way I can make the GC search for a "HiddenType*" 
 and run "freeObj" when the pointer is not found.


You can't turn an arbitrary pointer into a garbage collected 
object.
What you can do, is putting the pointer into a GCed object.

class Wrapper {
   this(HiddenType* p) { _p = p; } }
   ~this() { freeObj(_p); }
   alias _p this;
}

auto obj = new Wrapper(getObj());

Since 2.067.0 we also finalize heap allocated structs, so the 
wrapper can also be a struct.
Apr 20 2015