我应该在C＃dllimport本机方法调用中为参数释放内存吗？

Question

I used native method call in C# with DllImport feature. I want to know that should I release memory for method paremeters manually in native-side.

Currently, I send double[] array to native method, and native method get paretmers as double* type. Should I release double* in native method?

Answer 1

No, you should let .NET handle the memory management itself. The native code marshaller follows the basic rules for COM interop, which also happen to work most of the time for P/Invoke, since Win32 also follows the rules. (There are exceptions, but they'd be called out in the Windows API documentation).

Since you wrote both ends of the P/Invoke call, you should follow those same rules to make your life easy. As far as memory allocations are concerned, most of the time the caller is responsible for freeing any memory that crosses the P/Invoke boundary, since the callee doesn't know if/when it's safe to do so. This includes:

• If you allocate memory for a parameter and pass it in
• If there is an out parameter or return value that is allocated by the callee and returned

In both cases, only the caller knows when the memory is no longer needed and is safe to be freed. In the case of a P/Invoke call, the run-time marshaller knows this, and it will allocate memory to marshal your double[] to a double * before it makes the call, then free that memory when the call returns. Depending on the combination of ref , out , [In] or [Out] attributes, it may or may not try to copy the data back into your double[] , but it will always free that memory.