Bug#151065: g++: destructor called twice

[Peter Bastian <peter@luft.iwr.uni-heidelberg.de>]

Package: g++
Version: 2:2.95.4-14
Severity: normal

Hi !

We have problems with a C++ program reported in detail below.
It is not a Debian specific problem. In particular we checked:
- there is the same problem using GNU C++ compiler on SuSE Linux
  and MacOS X
- Code compiles and executes properly on MacOS using the
  CodeWarrior compiler
- Problem does not go away with g++ version 3.0

The code below compiles but when the expression
z = 3.0*x in the main function is executed the destructur of some
temporary object is called twice, leading to a segmentation
fault.

In addition there is a second problem: When the line
z = 3.0*x in main() is changed to z = x*3.0 the compiler
tries to instantiate the function template
T_leaftype operator* (double alpha, T_leaftype x) with
T_leaftype=double, but it should use the method operator*(double)
of class ScalarVector which is inherited from Vector<ScalarVector>

The code compiles and executes properly with the
CodeWarrior compiler on MacOS.

Thanks for considering this problem

------------------------>---<-----------------------------
#include<iostream>
#include<string>

using namespace std;

// The base class
template <class T_leaftype>
class Vector {
public:
	T_leaftype operator* (double alpha);
protected:
	Vector () {}
private:
	T_leaftype& asLeaf ()
		{ return static_cast<T_leaftype&>(*this);}
} ;

template <class T_leaftype>
inline T_leaftype Vector<T_leaftype>::operator* (double alpha)
{
	T_leaftype z(asLeaf());
	return z;
}

template <class T_leaftype>
inline T_leaftype operator* (double alpha, T_leaftype x)
{
	return x.operator*(alpha);
}

// The derived class
class ScalarVector : public Vector<ScalarVector> {
public:
	ScalarVector (int elements);
	ScalarVector (const ScalarVector&);
	~ScalarVector ();
private:
	int n;     // number of doubles
	double *v; // array of values
} ;

ScalarVector::ScalarVector (int elements)
{
	n = elements;
	v = new double[n];
	cout << "making ScalarVector v=" << v << endl;
}

ScalarVector::ScalarVector (const ScalarVector& x)
{
	n = x.n;
	v = new double[n];
	for (int i=0; i<n; i++) v[i] = x.v[i];
	cout << "making ScalarVector v=" << v << endl;
}

ScalarVector::~ScalarVector ()
{
	cout << "delete ScalarVector v=" << v << endl;
	delete[] v;
}

// main program
int main ()
{
	ScalarVector x(3), z(3);

	z = 3.0*x;
}




-- System Information
Debian Release: 3.0
Architecture: i386
Kernel: Linux luft 2.4.18 #1 Wed Jun 12 14:53:15 CEST 2002 i686
Locale: LANG=de_DE, LC_CTYPE=de_DE

Versions of packages g++ depends on:
ii  cpp                          2:2.95.4-14 The GNU C preprocessor.
ii  g++-2.95                     1:2.95.4-7  The GNU C++ compiler.
ii  gcc-2.95                     1:2.95.4-7  The GNU C compiler.



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