Question

In my static lib project(target:sdk.a), I used an extern function like this:

// in the PlatformUnity.h file
extern "C"{
    extern UIView * UnityGetGLView();  
    extern UIViewController * UnityGetGLViewController();

}

// in the PlatformUnity.mm file (*.mm NOT the *.m)

UIView * funcA(){
    return UnityGetGLView();
}

UIViewController * funcB(){
    return UnityGetGLViewController();
}

In another project named Unity-iPhone.xcodeproj, I used the SDK.a .
And there’s a file named AppController.mm contains the code below:

static UIViewController* sGLViewController = nil;
UIViewController* UnityGetGLViewController()
{
   return sGLViewController;
}
static UIView* sGLView = nil;
UIView* UnityGetGLView()
{
    return sGLView;
}

When I build the Unity-iPhone.xcodeproj, It tells me that it can’t find the function UnityGetGLView(). link error below:

Undefined symbols for architecture armv7:
  "_UnityGetGLViewController", referenced from:_funcB in SDK.a(PlatformUnity.o)
  "_UnityGetGLView", referenced from:_funcA in SDK.a(PlatformUnity.o)

This two function are really defined in AppController.mm But why I can’t find it when link? The other linker flag of Unity-iPhone.xcodeproj is below:

-all_load -weak_framework CoreMotion -weak-lSystem

Answer 1

I was able to solve this problem. The reason was I hadn’t added extern “C” to “UnityGetGLViewController” method. Compiler was compiling it as C++ function but actually it has to be compiled as C function.

i.e. Use following Code snippets

extern "C"
{
    extern UIViewController* UnityGetGLViewController();
}