我在玩埃里克·利珀特的Ref<T>
班级来自here https://stackoverflow.com/questions/2980463/how-do-i-assign-by-reference-to-a-class-field-in-c/2982037#2982037。我在 IL 中注意到,两个匿名方法看起来都在使用相同的生成类,尽管这意味着该类有一个额外的变量。
虽然只使用一个新的类定义似乎有些合理,但令我感到非常奇怪的是,只有一个实例<>c__DisplayClass2
被建造。这似乎意味着这两个实例Ref<T>
引用相同的<>c__DisplayClass2
这是不是意味着y
无法收集,直到vart1
被收集,这可能发生得晚得多joik
回报?毕竟,不能保证某些白痴不会编写直接访问的函数(直接在 IL 中)y
通过vart1
aftrer joik
返回。也许这甚至可以通过反射来完成,而不是通过疯狂的 IL。
sealed class Ref<T>
{
public delegate T Func<T>();
private readonly Func<T> getter;
public Ref(Func<T> getter)
{
this.getter = getter;
}
public T Value { get { return getter(); } }
}
static Ref<int> joik()
{
int[] y = new int[50000];
int x = 5;
Ref<int> vart1 = new Ref<int>(delegate() { return x; });
Ref<int[]> vart2 = new Ref<int[]>(delegate() { return y; });
return vart1;
}
运行 IL DASM 确认vart1
and vart2
都用过<>__DisplayClass2
,其中包含 x 和 y 的公共字段。 joik的IL:
.method private hidebysig static class Program/Ref`1<int32>
joik() cil managed
{
// Code size 72 (0x48)
.maxstack 3
.locals init ([0] class Program/Ref`1<int32> vart1,
[1] class Program/Ref`1<int32[]> vart2,
[2] class Program/'<>c__DisplayClass2' '<>8__locals3',
[3] class Program/Ref`1<int32> CS$1$0000)
IL_0000: newobj instance void Program/'<>c__DisplayClass2'::.ctor()
IL_0005: stloc.2
IL_0006: nop
IL_0007: ldloc.2
IL_0008: ldc.i4 0xc350
IL_000d: newarr [mscorlib]System.Int32
IL_0012: stfld int32[] Program/'<>c__DisplayClass2'::y
IL_0017: ldloc.2
IL_0018: ldc.i4.5
IL_0019: stfld int32 Program/'<>c__DisplayClass2'::x
IL_001e: ldloc.2
IL_001f: ldftn instance int32 Program/'<>c__DisplayClass2'::'<joik>b__0'()
IL_0025: newobj instance void class Program/Ref`1/Func`1<int32,int32>::.ctor(object,
native int)
IL_002a: newobj instance void class Program/Ref`1<int32>::.ctor(class Program/Ref`1/Func`1<!0,!0>)
IL_002f: stloc.0
IL_0030: ldloc.2
IL_0031: ldftn instance int32[] Program/'<>c__DisplayClass2'::'<joik>b__1'()
IL_0037: newobj instance void class Program/Ref`1/Func`1<int32[],int32[]>::.ctor(object,
native int)
IL_003c: newobj instance void class Program/Ref`1<int32[]>::.ctor(class Program/Ref`1/Func`1<!0,!0>)
IL_0041: stloc.1
IL_0042: ldloc.0
IL_0043: stloc.3
IL_0044: br.s IL_0046
IL_0046: ldloc.3
IL_0047: ret
} // end of method Program::joik