c++ - How to use smart pointer in this situation -

i want use smart pointer in following situation:

   some_struct* ptr = new some_struct;    ptr->some_member = new byte[100];    callsomeapi(ptr); 

now api can either return error or pass in both cases want delete object , 1 way can write delete statement during error exit , during normal exit.

but how can use smart pointer these pointers ? smart pointers mean unique_ptr, shared_ptr , etc. whichever can work !

thanks!

i assume cannot modify smoe_struct add destructor it. leaves 2 options: custom deleter, , encapsulation.

first, create custom deleter use std::unique_ptr:

struct some_struct_deleter {   void operator() (some_struct *p) const   {     delete[] p->some_member;     delete p;   } };  std::unique_ptr<some_struct, some_struct_deleter> ptr{new some_struct}; ptr->some_member = new byte[100]; callsomeapi(ptr.get()); 

if find that, unlike situation described in question, shared ownership suit better exclusive one, can use deleter shared_ptr well, this:

std::shared_ptr<some_struct> ptr{new some_struct, some_struct_deleter{}}; ptr->some_member = new byte[100]; callsomeapi(ptr.get()); 

a second option, find preferable, wrap some_struct:

struct some_struct_plus_plus {   some_struct s;   ~some_struct_plus_plus()   {     delete[] s.some_member;   }    some_struct_plus_plus()   {     s.some_member = new byte[100];   } };  std::unique_ptr<some_struct_plus_plus> ptr{new some_struct_plus_plus}; callsomeapi(&ptr->s); 

you "wrap" making some_struct_plus_plus derive some_struct instead of aggregating it, give direct access members without need go through s. @ same time, lead memory leaks if cast some_struct_plus_plus* some_struct* , called delete on it.