throwing dtor: %%justified use cases

Status — still I don’t have a well-justified use case.

I feel throwing dtor is frowned upon but not “illegal”. In practice it’s seldom done by design. When used, it’s not worth the analysis. In interviews, however, this receives disproportionate attention.

However, in practice, there are reasons to break the rule. Suppose I have

int i1, i2;// temp variables,
try{
  i1 = myobj->eat();
  myobj->drink(&i1);
  //....
  delete myobj;
}catch(business_exception & be){
  //handle exception using the temp variables i1, i2 etc
}

Since eat(), drink() etc and dtor all throw the same business_exception, this code is clean and maintainable. If we need to throw more than one exception type from those 3 functions, we can easily add the code. The same exception handler is used as a catch-all.

It would be messy to pass the temp variables i1, i2 etc into myobj dtor and replicate the same exception-handling logic therein.

So in this case, I’d make myobj dtor throw business_exception.

Now, as described in [[moreEffC++]] myobj dtor is invoked as part of stack unwinding due to another exception? [1] Well, in this case, I know that’s a fatal scenario and I do want system to crash anyway, like an assertion error, so the terminate() behavior is not unacceptable.

In other words, myobj’s class is written such that its dtor should throw exception only under normal object destruction and should never be part of an exceptional stack unwinding. In such a case, no one should misuse this class in an exception-unsafe context. If they ignore the restrictions on this class, they could get this dtor invoked as part of an exceptional stack unwinding, and the consequence is something they must deal with.

[1] in c++11, system will trigger std::terminate() whether or not this is part of unwinding. See https://akrzemi1.wordpress.com/2011/09/21/destructors-that-throw/

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