如何在C＃和未管理的C ++库之间传递引用指针？(How to pass a Reference

如何在C＃和未管理的C ++库之间传递引用指针？(How to pass a Reference-to-Pointer between between C# and an un-managed C++ Library?)

在我的C / C ++库中，我有一个这样的原型函数：

long myFunction( const wchar_t*& pszOutput)

Dll为pszOutput分配内存并释放它。

如何从C＃调用此函数？

我已经尝试了以下几行的很多变化（使用MarshalAs，......），但是在退出myFunction时我总是遇到崩溃：

[DllImport("mydll.dll", EntryPoint = "myFunction", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)] private static extern long myFunction(ref string szOutput);

有谁知道，怎么做？

In my C/C++ Library, I've a function with such a prototype:

long myFunction( const wchar_t*& pszOutput)

The Dll allocates the memory for pszOutput and deallocates it too.

How do I call this function from C# ?

I've tried a lot of variation of the following line (with out, with MarshalAs, ...), but I always get a crash when exiting myFunction:

[DllImport("mydll.dll", EntryPoint = "myFunction", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)] private static extern long myFunction(ref string szOutput);

Does anyone knows, how to do that?

最满意答案

如果你在Windows上，C ++ long不是C＃ long ，通常是C＃ int 。 用C ++检查sizeof(long) 。 如果它是4那么它是int 。

尝试传递out IntPtr szOutput ，然后将Marshal.PtrToStringUni()与返回的IntPtr 。

有关类似问题，请参阅例如PInvoke和char ** 。

If you are on Windows, C++ long isn't C# long, it is normally C# int. Check the sizeof(long) in C++. If it is 4 then it is int.

Try passing a out IntPtr szOutput, then use the Marshal.PtrToStringUni() with the returned IntPtr.

See for example PInvoke and char** for a similar problem.