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digitalmars.D - How does D allocate objects?

reply Tomás Rossi <Tomás_member pathlink.com> writes:
Coming from previous discussions about the GC and reading later answers, i think
i'm a little confused: 
1) Objects in D are ONLY heap-allocated and never stack-allocated?
2) Can you create static objects in D?

If the anwer to (2) is NO then i suppose something like this is forbidden:

MyObject myobj_instance(initializer params...);

Thanks


Tom
Oct 29 2005
next sibling parent Hasan Aljudy <hasan.aljudy gmail.com> writes:
Tomás Rossi wrote:

 Coming from previous discussions about the GC and reading later answers, i
think
 i'm a little confused: 
 1) Objects in D are ONLY heap-allocated and never stack-allocated?
 2) Can you create static objects in D?
 
 If the anwer to (2) is NO then i suppose something like this is forbidden:
 
 MyObject myobj_instance(initializer params...);
 
 Thanks
 
 
 Tom


As far as I understand, Objects in D are always references, never values.

There are certain circumistances where objects maybe allocated on the 
stack, but even then, the "new" keyword must be used! And I suspect that 
these circumistances are not guaranteed to create the objects on the 
stack, i.e. it's the compiler's dicision (implementation dependet).

I only know one such circumistance: auto (raii) objects that don't have 
a destructor.
Oct 29 2005
prev sibling next sibling parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Tomás Rossi" <Tomás_member pathlink.com> wrote in message 
news:dk1buh$1jcb$1 digitaldaemon.com...

 1) Objects in D are ONLY heap-allocated and never stack-allocated?


You can override this behavior by writing your own class allocator (custom 
new operator per-class).  It's in the docs: 
http://www.digitalmars.com/d/memory.html#stackclass


 2) Can you create static objects in D?


You mean something like

class A
{
    static A someA;

    static this()
    {
        someA = new A();
    }
}

That?  or have I missed your point?
Oct 30 2005
parent Tomás Rossi <Tomás_member pathlink.com> writes:
In article <dk3dso$pf1$1 digitaldaemon.com>, Jarrett Billingsley says...

"Tomás Rossi" <Tomás_member pathlink.com> wrote in message 
news:dk1buh$1jcb$1 digitaldaemon.com...

 1) Objects in D are ONLY heap-allocated and never stack-allocated?


You can override this behavior by writing your own class allocator (custom 
new operator per-class).  It's in the docs: 
http://www.digitalmars.com/d/memory.html#stackclass


 2) Can you create static objects in D?


You mean something like

class A
{
    static A someA;

    static this()
    {
        someA = new A();
    }
}

That?  or have I missed your point? 


I guess that would be a good example.

PS: The example i gave was about question 1).

Tom
Oct 30 2005
prev sibling next sibling parent reply Mike Parker <aldacron71 yahoo.com> writes:
Tomás Rossi wrote:


 1) Objects in D are ONLY heap-allocated and never stack-allocated?


Struct instances can be alloctated statically:

SomeStruct s;
s.somefield = 1;

Class instances are heap allocated and can only be newed:

MyClass c = new MyClass(); // <- OK
MyClass c();	// <-- not OK


 2) Can you create static objects in D?
 
 If the anwer to (2) is NO then i suppose something like this is forbidden:
 
 MyObject myobj_instance(initializer params...);


If you need to do this in a method/function for some class instance that 
you wish to be auto-destructed when it goes out of scope, use the auto 
keyword:

void MyFunc()
{
    // c will be destructed when it goes out of scope
    auto MyClass c = new MyClass();
}

If there's something you wish to statically allocate during app startup, 
use module constructors.

module mypackage.mymodule;

class MyClass
{
    public this()
    {
       doSomething();
    }
}
// 'static' instance
MyClass c;

// module constructor
static this()
{
    c = new MyClass();
}

// you can also have module destructors
static ~this()
{
}
Oct 30 2005
parent Tomás Rossi <Tomás_member pathlink.com> writes:
In article <dk3oob$1c5c$1 digitaldaemon.com>, Mike Parker says...

Tomás Rossi wrote:


 1) Objects in D are ONLY heap-allocated and never stack-allocated?


Struct instances can be alloctated statically:

SomeStruct s;
s.somefield = 1;

Class instances are heap allocated and can only be newed:

MyClass c = new MyClass(); // <- OK
MyClass c();	// <-- not OK


 2) Can you create static objects in D?
 
 If the anwer to (2) is NO then i suppose something like this is forbidden:
 
 MyObject myobj_instance(initializer params...);


If you need to do this in a method/function for some class instance that 
you wish to be auto-destructed when it goes out of scope, use the auto 
keyword:

void MyFunc()
{
    // c will be destructed when it goes out of scope
    auto MyClass c = new MyClass();
}

If there's something you wish to statically allocate during app startup, 
use module constructors.

module mypackage.mymodule;

class MyClass
{
    public this()
    {
       doSomething();
    }
}
// 'static' instance
MyClass c;

// module constructor
static this()
{
    c = new MyClass();
}

// you can also have module destructors
static ~this()
{
}


Ok thank you very much!, you've cleared my mind.

Tom
Oct 30 2005
prev sibling parent Dave <Dave_member pathlink.com> writes:
In article <dk1buh$1jcb$1 digitaldaemon.com>, Tomás Rossi says...

Coming from previous discussions about the GC and reading later answers, i think
i'm a little confused: 
1) Objects in D are ONLY heap-allocated and never stack-allocated?
2) Can you create static objects in D?

If the anwer to (2) is NO then i suppose something like this is forbidden:

MyObject myobj_instance(initializer params...);

Thanks


Tom


Here's a number of ways to allocate class objects:

http://digitalmars.com/d/memory.html
Oct 30 2005