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I have the following lines of code:

SomeClass a;
SomeClass b = new SomeClass();
SomeClass c = new SomeClass()
{
    Foo="sss",
    Bar="dddd"
};

Whats the size (in memory) of the class instances a, b and c?

How much memory get assigned to each variable?

Haukinger
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mehrdad hajiaghazadeh
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    The actual variables are all the same size since they are references. And the actual objects in the heap will be the same size as well (note that the strings will be separate objects that this object has a reference two). And of course `a` does not actual reference any because it's `null`. https://stackoverflow.com/questions/3800882/how-big-is-an-object-reference-in-net – juharr Sep 11 '17 at 14:56
  • And what is on the heap and what is on teh stack is actually a Framework implementation detail. As is string interning. And JiT Compiling might just disapear a because it is never used and it is dead code. So: Anything between the maximum and minimum amount possible, depending on the Runtime running it. The bigger question is: Why do you ask? What kind of micro-optimisation or faulty path are you on? – Christopher Sep 11 '17 at 15:27

1 Answers1

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When you instantiate b and c, memory is automatically allocated, you don't have to handle it yourself. You can forget that part, that's the managed magic part, and garbage collector will take care of freeing the memory space for you, once these objects aren't needed anymore (no pointers to it...). Still, b and c take the same memory size, since it's the same type. a takes no space since it's not initialized yet.

KitAndKat
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  • `a` does take space in the stack for the actual variable, it just does not reference anything in the heap. – juharr Sep 11 '17 at 15:02
  • the c# compiler and JIT usually get rid of unused variables, removing them, thus allocating no memory right ? – KitAndKat Sep 11 '17 at 15:06
  • This is just a code snippet so there could be an `if` latter that does set `a` in which case it cannot be optimized away, but yeah it would likely compile as if `a` were not even there. – juharr Sep 11 '17 at 15:08
  • But that if statement might also be dead code, because a is never set. The compiler/JiT Compiler is about smart enough to catch those. Especially if 'a' is private and this is not part of a partical class. – Christopher Sep 11 '17 at 15:29