为什么不'；t IntPtr需要unsafe关键字

本文关键字：需要 unsafe 关键字 IntPtr 为什么不 | 更新日期: 2023-09-27 18:00:27

当您在C#中使用类似int*的指针时，您需要使用unsafe关键字，但当您使用IntPtr时，您不需要。这些有什么区别？他们都可以指向一个地址。

垃圾收集器如何处理这两种类型？他们的处理方式不同吗？如果是，有什么区别？如果没有，为什么需要unsafe关键字？

编辑：非常感谢大家到目前为止的回答，但我想知道的是框架和垃圾收集器如何以不同的方式处理它们，而不是MSDN对IntPtr的定义。只需要一次谷歌搜索就可以到达那里。我想知道为什么IntPtr不需要unsafe关键字？我想了解一下为什么我们可以在没有关键字的情况下使用它。

为什么不'；t IntPtr需要unsafe关键字

根据MSDN：

http://msdn.microsoft.com/en-gb/library/system.intptr（v=vs.100）.aspx

它只是"指针或句柄"的表示

我一直在阅读GC如何与其他托管类型不同地处理IntPtr，并且我没有发现任何文档或文章表明IntPtr的收集方式有任何不同，即一旦IntPtr超出范围，它就可能是GC’d。

关于为什么没有使用unsafe关键字阅读已接受的答案，特别是更新：

不安全代码对安全代码有影响吗？

IntPtr的实现中已经指定了unsafe（请参阅下面IntPtr实现中的字段声明），因此使用IntPtr的类不必将其使用的IntPtr的任何使用标记为unsafe，否则它将一直级联到其他类，这些类可能在实现中使用具有不安全代码的类型。

除了unsafe代码不是IntPtr之外，字段private unsafe void* m_value;是unsafe，您没有直接使用它

// Type: System.IntPtr
// Assembly: mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:'Windows'Microsoft.NET'Framework'v4.0.30319'mscorlib.dll
using System.Globalization;
using System.Runtime;
using System.Runtime.ConstrainedExecution;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;
using System.Security;
namespace System
{
  [ComVisible(true)]
  [__DynamicallyInvokable]
  [Serializable]
  public struct IntPtr : ISerializable
  {
    [SecurityCritical]
    private unsafe void* m_value;
    public static readonly IntPtr Zero;
    [__DynamicallyInvokable]
    public static int Size
    {
      [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success), TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get
      {
        return 4;
      }
    }
    [SecuritySafeCritical]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    [__DynamicallyInvokable]
    public IntPtr(int value)
    {
      this.m_value = (void*) value;
    }
    [SecuritySafeCritical]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    [__DynamicallyInvokable]
    public IntPtr(long value)
    {
      this.m_value = (void*) checked ((int) value);
    }
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    [SecurityCritical]
    [CLSCompliant(false)]
    [TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
    public IntPtr(void* value)
    {
      this.m_value = value;
    }
    [SecurityCritical]
    private IntPtr(SerializationInfo info, StreamingContext context)
    {
      long int64 = info.GetInt64("value");
      if (IntPtr.Size == 4 && (int64 > (long) int.MaxValue || int64 < (long) int.MinValue))
        throw new ArgumentException(Environment.GetResourceString("Serialization_InvalidPtrValue"));
      this.m_value = (void*) int64;
    }
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    public static explicit operator IntPtr(int value)
    {
      return new IntPtr(value);
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    public static explicit operator IntPtr(long value)
    {
      return new IntPtr(value);
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    [SecurityCritical]
    [CLSCompliant(false)]
    public static explicit operator IntPtr(void* value)
    {
      return new IntPtr(value);
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    [CLSCompliant(false)]
    public static explicit operator void*(IntPtr value)
    {
      return value.ToPointer();
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    public static explicit operator int(IntPtr value)
    {
      return (int) value.m_value;
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    public static explicit operator long(IntPtr value)
    {
      return (long) (int) value.m_value;
    }
    [SecuritySafeCritical]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    public static bool operator ==(IntPtr value1, IntPtr value2)
    {
      return value1.m_value == value2.m_value;
    }
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    public static bool operator !=(IntPtr value1, IntPtr value2)
    {
      return value1.m_value != value2.m_value;
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    public static IntPtr operator +(IntPtr pointer, int offset)
    {
      return new IntPtr(pointer.ToInt32() + offset);
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    public static IntPtr operator -(IntPtr pointer, int offset)
    {
      return new IntPtr(pointer.ToInt32() - offset);
    }
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [SecuritySafeCritical]
    internal unsafe bool IsNull()
    {
      return (IntPtr) this.m_value == IntPtr.Zero;
    }
    [SecurityCritical]
    unsafe void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
    {
      if (info == null)
        throw new ArgumentNullException("info");
      info.AddValue("value", (long) (int) this.m_value);
    }
    [SecuritySafeCritical]
    [__DynamicallyInvokable]
    public override unsafe bool Equals(object obj)
    {
      if (obj is IntPtr)
        return this.m_value == ((IntPtr) obj).m_value;
      else
        return false;
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    [__DynamicallyInvokable]
    public override unsafe int GetHashCode()
    {
      return (int) this.m_value;
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [__DynamicallyInvokable]
    public unsafe int ToInt32()
    {
      return (int) this.m_value;
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [SecuritySafeCritical]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [__DynamicallyInvokable]
    public unsafe long ToInt64()
    {
      return (long) (int) this.m_value;
    }
    [SecuritySafeCritical]
    [__DynamicallyInvokable]
    public override unsafe string ToString()
    {
      return ((int) this.m_value).ToString((IFormatProvider) CultureInfo.InvariantCulture);
    }
    [SecuritySafeCritical]
    [__DynamicallyInvokable]
    public unsafe string ToString(string format)
    {
      return ((int) this.m_value).ToString(format, (IFormatProvider) CultureInfo.InvariantCulture);
    }
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    public static IntPtr Add(IntPtr pointer, int offset)
    {
      return pointer + offset;
    }
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    [ReliabilityContract(Consistency.MayCorruptInstance, Cer.MayFail)]
    public static IntPtr Subtract(IntPtr pointer, int offset)
    {
      return pointer - offset;
    }
    [SecuritySafeCritical]
    [CLSCompliant(false)]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
    public unsafe void* ToPointer()
    {
      return this.m_value;
    }
  }
}

IntPtr是一种托管类型，用于获取Windows操作系统的本机句柄。您不应该将它与int*这样的实际指针混淆。

请参阅MSDN以获取更多参考。

IntPtr本质上只是指针类型的托管表示。您可以在不安全的上下文中自由地将任何指针类型强制转换为IntPtr。从本质上讲，IntPtr只是void*的一个薄薄的包装（IIRC包含一个私有的void*字段）。

它通常在与非托管代码的互操作过程中（通过PInvoke或Marshal类）作为非托管指针类型的就地替换，因为与指针一样，IntPtr的大小随体系结构而变化（x86系统上为4字节，x64系统上为8字节）。

一个相关的问题。。。为什么dllimport不需要不安全的上下文？

我怀疑IntPtr和dllimport不需要不安全上下文的原因是为了使VB.NET（没有不安全的）能够轻松访问本机API。

然而，dllimport、IntPtr及其相互作用肯定存在"不安全"之处。

将无效参数交给dllimport入口点可能会导致崩溃，或者更糟的是，会悄悄损坏内存。这意味着在我看来，任何执行dllimport的代码都是"不安全的"。此外，如果该代码将IntPtr从安全代码泄漏到dllimport入口点，那么它本质上就是泄漏的——它"不安全"地泄漏到该安全代码中，因为安全代码可能会修改IntPtr使其无效。

当我使用dllimport时，我更喜欢将指针键入为不安全的结构指针，而不是IntPtr。这有两大好处。首先，它为我提供了不同类型的本机指针的类型检查。其次，它可以防止危险的非托管本机指针泄漏到"安全"代码中。

http://www.codeproject.com/script/Articles/ArticleVersion.aspx?aid=339290&av=638710

http://software.1713.n2.nabble.com/using-unsafe-struct-instead-of-IntPtr-with-PInvoke-td5861023.html

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