Exceptions as smart pointers

Long ago I've posted some messages on this topic, in particular this one:
Message-ID: <410A48AB.95A97D57@iobox.com>
http://groups.google.com/group/comp.lang.c++.moderated/msg/41de6076288f7c89

Now I've finished my "C++ multithreading" tutorial and opened a
discussion in comp.programming.threads:
Message-ID: <4899c3e1$0$90276$14726298@news.sunsite.dk>
http://groups.google.com/group/comp.programming.threads/msg/b52ce202a371778b

But there exist some points that deserve C++ specific attention. And one
of these points is "exceptions being thrown as smart pointers to actual
exception objects".

In particular, the object is being thrown is always sh_ptr<Exception>:
typedef sh_ptr<Exception> shException;
See http://ders.stml.net/cpp/mtprog/doc/exception_8hpp-source.html for
the details.

There also can be nested exceptions and used like this:

void f(mem_pool& mp, int i)
{
  shException exc(mp, 0);
  try {
      g(mp, i);
      return;
  }
  catch (shException she) { if (she->is<MsgException>()) throw; else
exc=she; }
  catch (...) { exc=recatchException(mp, _FLINE_); } // recatch!

  throw newException(_FLINE_, "Problems in f()", exc); // use as nested!
}

That is we recatch an exception and use it as a nested. The output can
look like this:
-----------------------------------8<-----------------------------------
    Exception #1:
ders::Exception [..\tst_exc.cpp:127], message: Problems in f()
ders::Exception [..\tst_exc.cpp:156], message: Problems in g()
ExampleException [..\tst_exc.cpp:136], message: Hello from g()

    Exception #2:
ders::Exception [..\tst_exc.cpp:127], message: Problems in f()
ders::Exception [..\tst_exc.cpp:156], message: Problems in g()
ders::StdExternException [..\tst_exc.cpp:154],
typeName="St12out_of_range", message: vector::_M_range_check

    Exception #3:
ders::Exception [..\tst_exc.cpp:127], message: Problems in f()
ders::Exception [..\tst_exc.cpp:156], message: Problems in g()
ders::UnknExternException [..\tst_exc.cpp:154], typeName="unknown",
message: Unknown exception

    Exception #4:
ders::UnknExternException [..\tst_exc.cpp:110], typeName="unknown",
message: Unknown exception

Non-empty exit message
-----------------------------------8<-----------------------------------
The sources are available here: http://ders.stml.net/cpp/mtprog/code.zip
So you can compile mtprog\derslib\tst\tst_exc.cpp yourself and se what's
going on.

Function recatchException() is defined as

shException recatchException(mem_pool& mp, const FileLine& location)
{
  try { throw; }
  catch (shException she) {
        return she;
  }
  catch (const std::exception& se) {
        return newStdExternException(mp, location, se.what(),
typeid(se).name());
  }
  catch (...) {
        return newUnknExternException(mp, location, "Unknown exception");
  }
}

And you can browse the documentation to quickly get the remaining
details: http://ders.stml.net/cpp/mtprog/doc/exception_8cpp-source.html
--
          With all respect, Sergey. http://ders.stml.net/
          mailto : ders at skeptik.net

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