[Bug c++/33799] New: Return value's destructor not executed when a local variable's destructor throws

[bitti at iki dot fi]

In C++, if a local variable's destructor throws after the return value object
has been created, the return value object is never destroyed!
G++ uses the allowed C++ return value optimisation and creates a return value
object directly without copying it. This is probably one source of the bug.

This bug manifests in all versions of g++ (3.2.3 - 4.2.2) I happened to have on
my machine, it also shows on both i686 and x86_64 architectures. It seems that
throwing destructors are rare enough so that this bug has gone unnoticed for
really long... :)

Test case:
-------- etest.cc --------------
#include <iostream>
#include <ostream>
using namespace std;

class X
{
public:
  X(bool throws) : throws_(throws)
  {
    cerr << "X::X() (" << throws_ << ")" << endl;
  }

  X(const X& x) : throws_(x.throws_)
  {
    cerr << "X::X(const X&) (" << throws_ << ")" << endl;
  }

  ~X()
  {
    cerr << "X::~X() (" << throws_ << ")" << endl;
    if (throws_) { throw 1; }
  }
private:
  bool throws_;
};

X f()
{
  X x(true);
  return X(false);
}

int main()
{
  try
  {
    f();
  }
  catch (...)
  {
    cerr << "Catch!" << endl;
  }
}
---------- end of etest.cc -----------
pulu:/home/bitti/tmp/t> g++ etest.cc
pulu:/home/bitti/tmp/t> ./a.out
X::X() (1)
X::X() (0)
X::~X() (1)
Catch!


-- 
           Summary: Return value's destructor not executed when a local
                    variable's destructor throws
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bitti at iki dot fi
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33799