非托管DLL函数正确调用约定 [英] Proper calling convention of unmanaged DLL function

问题描述

我试着写一个最基本的超简单的轻量包装的LibVLC DLL库。我并不需要访问很多，只是能力，播放暂停，停止媒体文件。我在看文档，我发现，说明LibVLC的旧版本的其他环节，但它是过时的最新版本。我也试过LibVLC.Net，但它也已经过时，我无法找到我要找的源$ C ​​$ C匹配到我想要导出功能。

I'm trying to write a bare-bones ultra-simple light-weight wrapper for the LibVLC DLL Library. I don't need access to much, just the ability to play pause and stop media files. I'm looking at the documentation and this other link I found that explains an older version of LibVLC, but it's outdated for the most recent version. I also tried LibVLC.Net but it too is outdated and I can't find what I'm looking for in the source code to match it to the functions I'm trying to export.

我有以下签名我想出口：

I have the following signature I'm trying to export:

libvlc_new (int argc, const char *const *argv)

说明：

argc    the number of arguments (should be 0)
argv    list of arguments (should be NULL)

这是方法我想。

And this is the method I'm trying.

[DllImport("libvlc", EntryPoint = "libvlc_new")]
public static extern IntPtr New(Int32 argc, String[] argv);

描述表明，它应该是一个数组，我认为这个问题是第二个参数。我尝试过：

The description suggests it should be an array, and I think the problem is the second argument. I've tried:

[MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPStr)] String[] argv

如根据此处，并且有一几个其他的选项，如一个字符串和StringBuilder的的建议这里但它仍然发生，每次我打电话的功能，我得到一个失衡的PInvoke堆栈。

as according to here, and there are a couple of other options such as a String and StringBuilder as suggested here but it still happens that every time I call the function I get an Imbalanced PInvoke stack.

我需要知道这个正确的调用约定，并且很可能其他几个，功能。 A的PInvoke傻瓜在线参考将是超好。

I need to know what the proper calling convention of this, and very likely several other, functions are. A "PInvoke For Dummies" online reference would be super good.

推荐答案

没有太多声明参数类型，如果只为NULL是允许的点。刚刚宣布它的IntPtr并通过IntPtr.Zero。

Not much point in declaring the argument type if only NULL is permitted. Just declare it IntPtr and pass IntPtr.Zero.

调试器是指出你忘了申报CallingConvention。这是不是默认的.NET，这是一个__cdecl函数。所以正确的声明将是：

The debugger is pointing out that you forgot to declare the CallingConvention. It is not the default for .NET, this is a __cdecl function. So the proper declaration would be:

[DllImport("libvlc", EntryPoint = "libvlc_new", 
     CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr New(int argc, IntPtr argv);

调用为：

New(0, IntPtr.Zero);

请尽量挑一个更好的名字......

Do try to pick a better name...

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