Question

我已经在调试模式下编译了一些测试代码，并用ILSpy反映了生成的程序集。这是我得到的IL：

.class private auto ansi beforefieldinit ArrayListBoxAndUnBox.Program
extends [mscorlib]System.Object
   {
// Nested Types
.class nested public auto ansi beforefieldinit Point
    extends [mscorlib]System.Object
{
    // Fields
    .field public int32 x
    .field public int32 y

    // Methods
    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        // Method begins at RVA 0x209f
        // Code size 7 (0x7)
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [mscorlib]System.Object::.ctor()
        IL_0006: ret
    } // end of method Point::.ctor

} // end of class Point


// Methods
.method private hidebysig static 
    void Main (
        string[] args
    ) cil managed 
{
    // Method begins at RVA 0x2050
    // Code size 59 (0x3b)
    .maxstack 2
    .entrypoint
    .locals init (
        [0] class [mscorlib]System.Collections.ArrayList list,
        [1] int32 i,
        [2] class ArrayListBoxAndUnBox.Program/Point p
    )

    IL_0000: nop
    IL_0001: newobj instance void [mscorlib]System.Collections.ArrayList::.ctor()
    IL_0006: stloc.0
    IL_0007: ldloc.0
    IL_0008: ldc.i4.1
    IL_0009: box [mscorlib]System.Int32
    IL_000e: callvirt instance int32 [mscorlib]System.Collections.ArrayList::Add(object)
    IL_0013: pop
    IL_0014: ldloc.0
    IL_0015: ldc.i4.0
    IL_0016: callvirt instance object [mscorlib]System.Collections.ArrayList::get_Item(int32)
    IL_001b: unbox.any [mscorlib]System.Int32
    IL_0020: stloc.1
    IL_0021: ldloc.0
    IL_0022: newobj instance void ArrayListBoxAndUnBox.Program/Point::.ctor()
    IL_0027: callvirt instance int32 [mscorlib]System.Collections.ArrayList::Add(object)
    IL_002c: pop
    IL_002d: ldloc.0
    IL_002e: ldc.i4.1
    IL_002f: callvirt instance object [mscorlib]System.Collections.ArrayList::get_Item(int32)
    IL_0034: castclass ArrayListBoxAndUnBox.Program/Point
    IL_0039: stloc.2
    IL_003a: ret
} // end of method Program::Main

.method public hidebysig specialname rtspecialname 
    instance void .ctor () cil managed 
{
    // Method begins at RVA 0x2097
    // Code size 7 (0x7)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: call instance void [mscorlib]System.Object::.ctor()
    IL_0006: ret
} // end of method Program::.ctor

} // end of class ArrayListBoxAndUnBox.Program

我看到.maxstack设置为2，但是当我手工完成代码时，我有时会在评估堆栈上得到3个元素。为什么？我是一个糟糕的IL堆栈计数器，还是这背后有意义？

在我的世界中，IL_0014上的第一个ldloc.0永远不会被删除，但也许只是我没有得到get_Item的callvirt如何工作。当我到达IL_0014时，我必须在我的纸叠上引用列表，然后在IL_0015，当0被推到评估堆栈时程序违反.maxstack。

我是新手，所以必定有一些不对的东西。也许我的计数是正确的，我对.maxstack的理解是错误的，或者可能是另一种方式。有人可以告诉我，如果我对.maxstack的理解是错误的，.maxstack会在运行时显示堆栈上的最大元素。或者如果我的计数错了？ Add是否删除对列表实例的引用？

编辑：这是我的计算方式。计数在IL代码运行之后：

IL_0000: 0 on stack
IL_0001: 1 on stack (the reference to array list)
IL_0006: 0 on stack
IL_0007: 1 on stack (the reference to arraylist)
IL_0008: 2 on stack (reference to arraylist and int 1)
IL_0009: 2 on stack (refernce to arraylist and reference to object that wrap 1)
IL_000e: 2 on stack (reference to arraylist and index to the added boxed int object)
IL_0013: 1 on stack (reference to arraylist)
IL_0014: 2 on stack (reference to arraylist and reference to arraylist)
IL_0015: 3 on stack (reference to arraylist and reference to arraylist and int 0)

我没有计算其余部分，因为我知道我遇到了错误。

由于

Answer 1

很难看出你哪里出错了。在执行指令后，在左侧注释堆栈深度：

0    IL_0000: nop
1    IL_0001: newobj instance void [mscorlib]System.Collections.ArrayList::.ctor()
0    IL_0006: stloc.0
1    IL_0007: ldloc.0
2    IL_0008: ldc.i4.1
2    IL_0009: box [mscorlib]System.Int32
1    IL_000e: callvirt instance int32 [mscorlib]System.Collections.ArrayList::Add(object)
0    IL_0013: pop
1    IL_0014: ldloc.0
2    IL_0015: ldc.i4.0
1    IL_0016: callvirt instance object [mscorlib]System.Collections.ArrayList::get_Item(int32)
1    IL_001b: unbox.any [mscorlib]System.Int32
0    IL_0020: stloc.1
1    IL_0021: ldloc.0
2    IL_0022: newobj instance void ArrayListBoxAndUnBox.Program/Point::.ctor()
1    IL_0027: callvirt instance int32 [mscorlib]System.Collections.ArrayList::Add(object)
0    IL_002c: pop
1    IL_002d: ldloc.0
2    IL_002e: ldc.i4.1
1    IL_002f: callvirt instance object [mscorlib]System.Collections.ArrayList::get_Item(int32)
1    IL_0034: castclass ArrayListBoxAndUnBox.Program/Point
0    IL_0039: stloc.2
0    IL_003a: ret

唯一不重要的是ArrayList.Add（）调用。它弹出两个堆栈值，ArrayList对象引用和Add（）参数。并向后推一个Add（）的返回值。

编辑后：这确实是你出错的地方。

为我解释maxstack指令

1 个答案: