A major design concern in modern software development frameworks is to ensure that mechanisms for updating code running on remote devices comply with given safety specifications. This paper presents a delta-oriented approach for implementing product lines where software reuse is achieved at the three levels of state-diagram modeling, C/ $$\text {C}^{_{_{_{++}}}} $$ source code and binary code. A safety specification is expressed on the properties of reusable software libraries that can be dynamically loaded at run time after an over-the-air update. The compilation of delta-engineered code is certified using the framework of proof-carrying code in order to guarantee safety of software updates on remote devices. An empirical evaluation of the computational cost associated with formal safety checks is done by means of experimentation.