直接数组初始化一个恒定值 [英] Direct array initialization with a constant value

问题描述

当你分配在C＃中一个新的阵列

Whenever you allocate a new array in C# with

new T[length]

数组项设置为吨默认这就是空的情况下 T 是一个引用类型或 T 的默认构造函数的结果，如果 T 是值类型。

the array entries are set to the default of T. That is null for the case that T is a reference type or the result of the default constructor of T, if T is a value type.

在我来说，我要初始化与的Int32 数组值-1：

In my case i want to initialize an Int32 array with the value -1:

var myArray = new int[100];
for (int i=0; i<myArray.Length; i++) { myArray[i] = -1; }

因此​​，存储器保留用于阵列之后，在CLR循环通过新分配的存储器，并设置所有条目为默认（INT）= 0。在此之后，我的code设置的所有项为-1。

So after the memory is reserved for the array, the CLR loops over the newly allocated memory and sets all entries to default(int) = 0. After that, my code sets all entries to -1.

这使得初始化多余的。是否JIT检测到并忽略初始化为0，如果没有，有没有办法直接初始化的内存的自定义值的部分？

That makes the initialization redundant. Does the JIT detect this and neglects the initialization to 0 and if not, is there a way to directly initialize a portion of memory with a custom value?

参照 C＃数组初始化 - 与非默认值使用 Enumerable.Repeat（值，长度）.ToArray（）是没有选择的，因为 Enumerable.ToArray 分配新的数组和复制值之后它

Referring to C# Array initialization - with non-default value , using Enumerable.Repeat(value, length).ToArray() is no option, because Enumerable.ToArray allocates a new array and copies the values to it afterwards.

推荐答案

这不是多余的。

假设一个异常的初始化循环中抛出。如果CLR没有先清除内存，您也许能够看到原始的未初始化的内存，这是一个非常糟糕的主意，特别是从安全角度来看。这就是为什么CLR保证任何新分配的内存擦拭到0位模式。

Suppose an exception is thrown during your initialization loop. If the CLR hasn't cleared the memory first, you might be able to "see" the original uninitialized memory, which is a very bad idea, particularly from a security standpoint. That's why the CLR guarantees that any newly allocated memory is wiped to a 0 bit pattern.

同样的道理也适用于在对象领域，顺便说一句。

The same argument holds for fields in an object, by the way.

我在两种情况下假设CLR可以检查你不会使数组可见别处结束初始化之前，但它是一个复杂的检查，以避免pretty简单的抹这种存储区。

I suppose in both cases the CLR could check that you're not going to make the array visible elsewhere before finishing initialization, but it's a complicated check to avoid a pretty simple "wipe this area of memory".

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