尝试分配指针容器时出现P/Invoke EntryPointNotFoundException

我试图在下面的Alsa函数上调用DllImport(从 documentation :

#define snd_seq_client_info_alloca( ptr )  __snd_alloca(ptr, snd_seq_client_info)

分配一个snd_seq_client_info_t 堆叠的容器

这里是我在C++中发现的一个实现 application 类似于我想在Mono中完成的任务:

snd_seq_client_info_t* cinfo;
snd_seq_client_info_alloca(&cinfo);

到目前为止,我所拥有的一切,但都不管用:

[DllImport(libasound.so.2)]
private static extern void snd_seq_client_info_alloca(out IntPtr ptr);

internal static void MyFunction ()
{
    IntPtr clientInfo = IntPtr.Zero;
    snd_seq_client_info_alloca(out clientInfo);
    // and then some more ...
}

但我有个例外:

System.EntryPointNotFoundException: snd_seq_client_info_alloca
at (wrapper managed-to-native)   
MonoMultiJack.ConnectionWrapper.Alsa.LibAsoundWrapper:snd_seq_client_info_alloca (intptr&)