Destructors should never emit exceptions. If functions called in a destructor may throw, the destructor should catch any exceptions, then swallow them or terminate the program.
1. Terminate the program if close throws, typically by calling abort:
DBConn::~DBConn() { try { db.close(); } catch (...) { // make log entry that the call to close failed; std::abort(); } }
2. Swallow the exception arising from the call to close:
DBConn::~DBConn() { try { db.close(); } catch (...) { //make log entry that the call to close failed; } }
If class clients need to be able to react to exceptions thrown during an operation, the class should provide a regular (i.e., non-destructor) function that performs the operation.
class DBConn { public: // ... void close() // new function for { // client use db.close(); closed = true; } ~DBConn() { if (!closed) { try { // close the connection db.close(); // if the client didn’t } catch (...) { // if closing fails, //make log entry that call to close failed; //note that and ... terminate or swallow } } } private: DBConnection db; bool closed; };