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.NET Forum / .NET Framework / General / October 2004Value Types - Structures
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 > Hi All, > Microsoft says that structures are value types. Also primitive data types [quoted text clipped - 4 lines] > Thanks in advance. > Faktujaa > Microsoft says that structures are value types. Also primitive data types > are value types. And memory for value types is allocated on the stack. 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. "new" just means "call a constructor". It doesn't have anything to do with where things are allocated.  SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too 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 > > Microsoft says that structures are value types. Also primitive data types > > are value types. And memory for value types is allocated on the stack. [quoted text clipped - 8 lines] > "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 The constructor probably actually sets member variables to *other* values, actually. It's not much use as a constructor otherwise... SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too 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 > > New has nothing to do with allocation of memory. It is used to call the > > constructor. [quoted text clipped - 4 lines] > The constructor probably actually sets member variables to *other* > values, actually. It's not much use as a constructor otherwise... > 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 Correct me if I'm wrong, but in C++, new is an operator whereas in VB New is a method name. SignatureChris 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 > > 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 > > Correct me if I'm wrong, but in C++, new is an operator whereas in VB New > is a method name. > 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 [quoted text clipped - 3 lines] > the memory on the stack. Any help on this is highly appreciated. Thanks in > advance. It just creates new instances, wherever they should go. It's as simple as that. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too > > 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 > > Correct me if I'm wrong, but in C++, new is an operator whereas in VB New > is a method name. I'm not sure that it counts as an operator as such, but it's certainly a keyword rather than a method. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too Jon (& faktujaa), > I'm not sure that it counts as an operator as such, but it's certainly > a keyword rather than a method. 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/vblr fVBSpec9_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/vclr fNewOpPG.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 >> > name(class). Actually i was thinking that by creating a variable with >> > new [quoted text clipped - 6 lines] > I'm not sure that it counts as an operator as such, but it's certainly > a keyword rather than a method. > 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. Did you read the article I linked to? It explains it all there. http://www.pobox.com/~skeet/csharp/memory.html SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too 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 > > 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 [quoted text clipped - 6 lines] > > http://www.pobox.com/~skeet/csharp/memory.html > 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 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. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too Free MagazinesGet these publications absolutely FREE for up to 12 months. 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