ERROR: EXTERNAL CALLS NOT SUPPORTED

This error can be caused by the compiler not finding a matching definition for a function that has been declared. For instance, if a given function is declared taking an int and defined taking a float:

__device__ int myfunc(int a);

...

int b = myfunc(123);

...

__device__ int myfunc(float a) {

 ...

}

–> External calls are not supported (found non-inlined call to myfunc)