UnityPluginLoad not called in native plugin

In my native plugin, I created the UnityPluginLoad / UnityPluginUnload function as what described in https://docs.unity3d.com/Manual/NativePluginInterface.html . However, I can't make the
UnityPluginLoad() be called when using the plugin, although my own functions could be called from Unity C# script without any problem.

In the C++ code, the UnityPluginLoad function is declared in the same way as the documentation:

#include "IUnityInterface.h"
extern "C" void UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API
UnityPluginLoad(IUnityInterfaces* unityInterfaces)​

I checked the exported names of the DLL, and can find UnityPluginLoad function there. Here is the list of the exported functions:

_Cleanup@0
_Initialize@0
_ReturnIntFunc@0
_SetLogFunction@4
_UnityPluginLoad@4
_UnityPluginUnload@0​

Among them, Cleanup(), Initialize(), ReturnIntFunc(), SetLogFunction() are all explicitly exported functions, and they all work fine. It seems UnitPluginLoad() is also exported with the same naming convention.

I'm using Unity 5.4.0f3-FTP. Might it be a Unity version or platform specific problem? Thank you very much!

 

I checked the sample and found the problem. It seems a .def file is necessary to prevent VC from mangling the name of UnityPluginLoad. The export name has to be "UnityPluginLoad". "_UnityPluginLoad@4" doesn't be recognized.

However, it's interesting that the native plugin system is more tolerate on the name mangling of user exported functions.

Thank you very much for your help!

 

I thought I had the same problem, but I just made a mistake in my code. I just tested it and it seems that at least in Unity v5.5 it is no longer needed to use a .def file. (Visual Studio 2015). I looked with DependencyWalker and the function names were not mangled. Maybe just using extern "C" fixes this also (because C++ mangles function names).

 

I just had this problem with 2017.1.1f1. I hope that the .def file requirements can be be added to the "Low-level Native Plugin Interface" documentation.

 

UnityRegisterRenderingPlugin() seems to cause UnityPluginLoad() not called.
If you use multiple plugins and one of them uses UnityRegisterRenderingPlugin() that also affects other plugin's UnityPluginLoad() not called.
Check if all the plugins use UnityRegisterRenderingPluginV5 instead of
UnityRegisterRenderingPlugin().

 

I just ran into this issue and followed the steps in this helpful article to resolve it:

https://medium.com/@bengreenier/building-native-unity-plugins-with-visual-studio-8f470e5af9ca

Like others have mentioned here, the issue is that the UnityPluginLoad function gets prefixed with an underscore when building for x86 (_UnityPluginLoad) unless you use a .def file. This article I linked to provides an example of a .def file and describes how to set it in Visual Studio.