DLL中的共享内存 [英] Shared memory in DLLs

问题描述

共享内存在DLL中如何工作？

当DLL附加到进程时，它使用与进程相同的内存地址。假设我们在DLL中有以下功能：

  int * data = 0; 
 int foo（）
 {
 if（！data）data = new int（random（））; 
 return * data; 
} 
  

当进程A调用此函数时，它将创建新对象（int），并返回值。
但现在进程B附加这个DLL。它调用foo（），但是我不明白它是如何工作的，因为 data 正在处理'内存空间。 B如何能够直接使用它？

解决方案

你是正确的，默认情况下，DLL不会在进程之间共享内存。在您的示例中，进程A和B都将获得单独的数据实例。

如果您有一个设计，您想要在DLL中共享全局变量在所有使用该DLL的进程中，您可以使用共享数据段，如这里。您可以通过共享数据段共享预先声明的数组和值类型，但您绝对不能共享指针。

How does sharing memory works in DLLs?

When DLL is attached to process, it uses the same memory addresses as process. Let's assume we have following function in DLL:

int * data = 0;
int foo()
{
    if (!data) data = new int(random());
    return *data;
}

When process A calls this function it creates new object (int) and returns its value. But now process B attaches this DLL. It calls foo() but I don't understand how would it work, because data is in process' A memory space. How would B be able to directly use it?

解决方案

You are correct, DLLs do NOT share memory across processes by default. In your example, both process A and B would get a separate instance of "data".

If you have a design where you want to have global variables within a DLL shared across all the processes that use that DLL, you can use a shared data segment as described here. You can share pre-declared arrays and value types through shared data segments, but you definitely can't share pointers.

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