I have the following code in C#
// test.Program
private static void Main()
{
int x = 5;
int y = 100;
Console.WriteLine(y + ", " + x);
}
And I'm reading the IL code, I've never programmed assembly before so I'm asking if what I each line does is correct.
.method private hidebysig static
void Main () cil managed
{
// Method begins at RVA 0x2058
// Code size 33 (0x21)
.maxstack 3 // maximum stack in this method is 3
.entrypoint // method is initial entry point
.locals init ( // reserves memory for x and y variables
[0] int32 x, // x variable is reserved on position 0 of the stack
[1] int32 y // y variable is reserved on position 1 of the stack
)
IL_0000: ldc.i4.5 // integer of 4 bytes in size and the value of 5 is loaded onto the evaluation stack position 0
IL_0001: stloc.0 // put evaluation stack position 0 into the stack position 0, the evaluation stack is emptied
IL_0002: ldc.i4.s 100 // integer of 4 bytes in size and the value of 100 is loaded onto the evaluation stack position 0
IL_0004: stloc.1 // put evaluation stack position 0 onto the stack position 1, the evaluation stack is emptied
IL_0005: ldloc.1 // load stack position 1 into the evaluation stack position 0
IL_0006: box [mscorlib]System.Int32 // box last valuetype placed on evaluation stack, replace valuetype with reference on evaluation stack position 0, do not empty stack
IL_000b: ldstr ", " // put reference to string on evaluation stack position 1
IL_0010: ldloc.0 // load stack position 0 into the evaluation stack position 2
IL_0011: box [mscorlib]System.Int32 // box last valuetype placed on evaluation stack, replace valuetype with reference on evaluation stack position 0, do not empty stack
IL_0016: call string [mscorlib]System.String::Concat(object, object, object) // call Concat, pass values on evaluation stack, empty evaluation stack, put result of concat on evaluationstack
IL_001b: call void [mscorlib]System.Console::WriteLine(string) // pass first value in evaluation stack
IL_0020: ret // return
} // end of method Program::Main
Do I understand this program correctly?
Pretty much; only thing I'd clarify is that the box (IL_0006 and IL_0011) is type specific, so it is explicitly constructing a box of type int
(it isn't just the "last valuetype").
Also, "empty evaluation stack" is misleading; that isn't quite right - for example, call
consumes a given number of positions - it doesn't "empty" it. There is never an "empty evaluation stack" semantic - it is always "consume a number of values, put back a number of values" (either of which may be zero).
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