Re: throwing dtors...

From:
"Chris M. Thomasson" <no@spam.invalid>
Newsgroups:
comp.lang.c++
Date:
Wed, 1 Oct 2008 20:28:00 -0700
Message-ID:
<L6XEk.4877$cs4.2705@newsfe01.iad>
"Chris M. Thomasson" <no@spam.invalid> wrote in message
news:k4XEk.16199$hX5.2021@newsfe06.iad...

Is it every appropriate to throw in a dtor? I am thinking about a simple
example of a wrapper around a POSIX file...
________________________________________________________________________

[...]

________________________________________________________________________

How to properly handle `EAGAIN' in dtor? Well, what about any error for
that matter? I am a C programmer and only code C++ for fun, and some
in-house projects. If I were really going to create C++ application and
release it into the wild, well, how would you advise me to handle the case
above? I am interested in how throwing in a dtor effects dynamic
destruction... Would something like the following be legal?

<pseudo code!!!!>
_______________________________________________________________
struct throw_from_dtor {
 int const m_status;

public:
 throw_from_dtor(int const status)
  m_status(status) {}

 int get_status() const { return m_status; }
};

class file {
 FILE* m_handle;

public:
 // [ctor];

 ~file() {
   int const status = fclose(m_handle);
   if (status) {
     throw throw_from_dtor(status);

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    // ummmm! well, stupid me forgot to store `errno' into the
exception!!!!!!

       throw throw_from_dtor(errno);

    // sorry about the non-sense! ;^(...

   }
 }
};

int main() {
 file* f = new file();
 try {
   delete f;
 } catch(throw_from_dtor const& e) {
   // handle error from `e.get_status()'
   delete f;
 }
 return 0;
}
_______________________________________________________________

?

or what about using smart pointer...

int main() {
 std::auto_ptr<file> f;
 try {
   f.reset(new file());
 } catch(throw_from_dtor const& e) {
   // handle error from `e.get_status()'
 }
}

?

Please keep in mind that refusing to not handle an error from `fclose'
could resule is HORRIBLE things down the road... Think massive data
lost... Perhaps __permanent__ data-! OUCH!!!

;^/

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