can anybody tell me why the size of an empty class is 1

[philiptabraham]

can anybody tell me why the size of an empty class is 1.and i also want to know why we cant create an object for an abstract class. Thanks in advance

[George L Jackson]

C++ requires freestanding empty objects to have non-zero size. Most compilers automatically insert a char into "empty" objects to satisfy this. However, if your empty class is a base class then it won't add any size to the derived class object. See: http://msdn2.microsoft.com/en-us/library/f42z47h2(VS.80).aspx[^] You cannot create an object directly from an abstract class since it contains virtual method(s) without implementation(s).

"We make a living by what we get, we make a life by what we give." --Winston Churchill

modified on Monday, December 10, 2007 3:25:41 PM

[Luc Pattyn]

Giving them the smallest possible non-zero size makes sure different objects result in different pointer/reference values, which is what you hope to get isn't it? :)

Luc Pattyn [Forum Guidelines] [My Articles]

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[Mark Salsbery]

philiptabraham wrote:

i also want to know why we cant create an object for an abstract class

If you could, the class wouldn't be abstract. It doesn't make sense to create an object of a class that has virtual functions that are NULL. Mark

Mark Salsbery Microsoft MVP - Visual C++ :java:

modified on Monday, December 10, 2007 3:15:35 PM

[George L Jackson]

Mark Salsbery wrote:

It doesn't make sense to create an object of a class that doesn't have a complete implementation.

You can make a class non-copyable by declaring a private copy constructor (and assignment operator) without an implementation!

"We make a living by what we get, we make a life by what we give." --Winston Churchill

[Mark Salsbery]

right. badly worded - I changed it a bit. It took a long time for CP to let me edit it (or reply to you :)). Mark

Mark Salsbery Microsoft MVP - Visual C++ :java: