Value Types - Structures

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Guest

Hi All,
Microsoft says that structures are value types. Also primitive data types
are value types. And memory for value types is allocated on the stack. Then
why we need new operator to allocate memory for structure value types and not
for primitive data types(they r allocated memory on stack as well)??? Please
help.
Thanks in advance.
Faktujaa
 
hi
the struct gets allocated on the stack.
What 'new ' does is initialize the value type's fields to null/zero

regards
Ansil
 
faktujaa said:
Microsoft says that structures are value types. Also primitive data types
are value types. And memory for value types is allocated on the stack.
Click to expand...

Memory for value types is only allocated on the stack in some cases.
See http://www.pobox.com/~skeet/csharp/memory.html
Then why we need new operator to allocate memory for structure value
types and not for primitive data types(they r allocated memory on
stack as well)??? Please help.
Click to expand...

"new" just means "call a constructor". It doesn't have anything to do
with where things are allocated.
 
New has nothing to do with allocation of memory. It is used to call the
constructor.
so by using the new with a structure , you are calling a constructor of the
structure which sets all its members variables to 0, false or null depending
on their type

Nishith Pathak
 
Nishith Pathak said:
New has nothing to do with allocation of memory. It is used to call the
constructor.
so by using the new with a structure , you are calling a constructor of the
structure which sets all its members variables to 0, false or null depending
on their type
Click to expand...

The constructor probably actually sets member variables to *other*
values, actually. It's not much use as a constructor otherwise...
 
Thanks for the inputs. Then how does CLR knows that it has to allocate the
memory on stack/heap. By this, i think it determines based on the type
name(class). Actually i was thinking that by creating a variable with new
keyword, we assign the memory on the heap as in C/C++. Anyways thanks for the
help but still the question of how does the CLR knows abt where to allocate
the memory is bothering me. Please help.
Faktujaa
 
name(class). Actually i was thinking that by creating a variable with new
keyword, we assign the memory on the heap as in C/C++. Anyways thanks for the
Click to expand...

Correct me if I'm wrong, but in C++, new is an operator whereas in VB New
is a method name.

--
Chris

dunawayc[AT]sbcglobal_lunchmeat_[DOT]net

To send me an E-mail, remove the "[", "]", underscores ,lunchmeat, and
replace certain words in my E-Mail address.
 
Hi,
Im was not talking of C++ and VB but of C#/VB.NET and C++/VB. Anyways im not
a VB guy so i don't know anything abt it. Also as per microsoft, the new
keyword can be used as an operator or as a modifier in C#. As an operator, is
used to create objects on the heap and invoke constructors. Then by using the
same new operator to create an object of structure type, why do it allocates
the memory on the stack. Any help on this is highly appreciated. Thanks in
advance.
faktujaa

Chris Dunaway" <"dunawayc[[at]_lunchmeat said:
name(class). Actually i was thinking that by creating a variable with new
keyword, we assign the memory on the heap as in C/C++. Anyways thanks for the
Click to expand...

Correct me if I'm wrong, but in C++, new is an operator whereas in VB New
is a method name.

--
Chris

dunawayc[AT]sbcglobal_lunchmeat_[DOT]net

To send me an E-mail, remove the "[", "]", underscores ,lunchmeat, and
replace certain words in my E-Mail address.
Click to expand...
 
faktujaa said:
Im was not talking of C++ and VB but of C#/VB.NET and C++/VB. Anyways im not
a VB guy so i don't know anything abt it. Also as per microsoft, the new
keyword can be used as an operator or as a modifier in C#. As an operator, is
used to create objects on the heap and invoke constructors. Then by using the
same new operator to create an object of structure type, why do it allocates
the memory on the stack. Any help on this is highly appreciated. Thanks in
advance.
Click to expand...

It just creates new instances, wherever they should go. It's as simple
as that.
 
faktujaa said:
Thanks for the inputs. Then how does CLR knows that it has to allocate the
memory on stack/heap. By this, i think it determines based on the type
name(class). Actually i was thinking that by creating a variable with new
keyword, we assign the memory on the heap as in C/C++. Anyways thanks for the
help but still the question of how does the CLR knows abt where to allocate
the memory is bothering me. Please help.
Click to expand...

Did you read the article I linked to? It explains it all there.

http://www.pobox.com/~skeet/csharp/memory.html
 
Correct me if I'm wrong, but in C++, new is an operator whereas in VB New
is a method name.
Click to expand...

I'm not sure that it counts as an operator as such, but it's certainly
a keyword rather than a method.
 
CLR determin the allocation on heap or stack by checking its type. For
example if it is int since it is been a System,int32 structure so it is
always be allocated on stack and if it string which represent. System.String
class then it is allocated on the Heap.CLR does not look for the new keyword
to allocate it in Heap or stack. New keyword is just to initialise the memory
through the use of constructor

Hope it helps you

Nishith
 
Nishith Pathak said:
CLR determin the allocation on heap or stack by checking its type. For
example if it is int since it is been a System,int32 structure so it is
always be allocated on stack
Click to expand...

No it won't. For instance:

class Test
{
int i;
}

The integer here is part of a class, and will always be on the heap,
despite being a value type. Claiming that value types are always
allocated on the stack is misleading and incorrect.

Please see the article I linked to previously.
 
Jon (& faktujaa),
I'm not sure that it counts as an operator as such, but it's certainly
a keyword rather than a method.
Click to expand...
VB.NET considers New an operator (when its not the identifier for the
constructor, aka a method name):

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vbls7/html/vblrfVBSpec9_6.asp

C# considers new an operator (when its not a modifier):

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vclrfNewOpPG.asp

In both case the New operator creates an "object" & calls a constructor. As
you know in the case of a value type the "object" is created "inline" (stack
or another object), while for reference types the "object" is created on the
heap.

I've always considered new an operator in C++ also, as the new operator (in
C++) also allocates space for the object & calls the constructor.

Hope this helps
Jay
 
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