Should any function be able to work in-place by default

If I am building a library for C++. Is it OK if some functions could not accept in-place operation? would it affect the standard property of the library?

For example:

void do_somthing(object const& input, object& output);

int main(){
   object a;
   object b;
   do_somthing(a, b);//OK
   do_somthing(a, a);//wrong
}

If it is OK, how should I tell that? for example should I put an assertion? throw exception? Just put it in the documentation and let it produces undefined behavior if someone insists to call it?

Some clarification:

In the OpenCV library, some function like cv::Canny can work in place like this:

cv::Canny(img,img,100,200);

However, cv::warpAffine can not as it was written in the documentation.