ldstr在内部实现newobj吗？

Question

As we all know strings are implicitly instantiated, meaning that we don't have to use new in order to get a reference to an object of one.

Because of this it was always my belief that the framework is taking care of this, and hence I would get identical IL if I did something like this:

String first = new String(new char[] {'a'});
string second = "a";

However it appears that the first line is done using newobj instance void [mscorlib]System.String::.ctor(char[]) and the second ldstr "a" .

So in order to obtain a string reference, does ldstr internally call newobj and where can I see the specification / details to back this up?

Answer 1

ldstr gives you the reference to the literal string as per the documentation (remember literal strings are interned per default, so they are only created once). The first statement creates a regular instance of string using the newobj instruction as expected.

Answer 2

string simply follows tha basic guideline for reference object types, that's why on new you see newobj .

Infact if you try to write something like this, it will not generate newobj :

int a = new int();
a = 2;  
Console.WriteLine(a);

The resulting IL will be

IL_0000:  ldc.i4.0    
IL_0001:  stloc.0     
IL_0002:  ldc.i4.2    
IL_0003:  stloc.0     
IL_0004:  ldloc.0     
IL_0005:  call        System.Console.WriteLine

if you write just

int a = 2;  
Console.WriteLine(a);

result IL will be

IL_0000:  ldc.i4.2    
IL_0001:  stloc.0     
IL_0002:  ldloc.0     
IL_0003:  call        System.Console.WriteLine

No difference from allocation point of view (there is missed line naturally), cause we are talking about value type.