get_error_info takes a const exception object and returns a pointer to const data object of respective error_info. But why is there no way of getting non-const pointer (which would allow to modify the data)? This is especially strange because operator << can be used to add data to a const exception object so I don't see reason for not being able to get modifiable data back (at least from non-const exception object). Having this would allow me to safely gather exception data before throwing or during exception propagation. What I wanted was to insert an empty vector of data to the preconstructed exception object. Then obtain the vector with get_error_info (since operator << adds a copy I have to get the actual object). Then call reserve on the obtained vector and start the actual operation. During the operation I can gather (possible) error data and safely add it to the vector since memory is already reserved. In the end if any error data was gathered I will throw the preconstructed exception object. In reasonable implementation this should be safe as well. (Similar thing might be done while propagating the exception.) With current code (lack of non-const get_error_info) it is not possible. I have to get the vector from exception object. Then add data to the vector (this may fail). Then again add vector to the exception object (overwriting old vector; this may fail). And in the end throw (if needed). Alternatively I could preconstruct vector, reserve space add data to it. Then in the end if I will throw the data vector is there for me. However I still have to add it to the exception object and this still may fail. Adam Badura