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From: charlie@genrad.com (Charlie D. Havener)
Newsgroups: comp.lang.c++
Subject: Borland Turbo C++ Bug - invokes destructor twice for a local object!
Keywords: Turbo C++ destructor bug
Message-ID: <37824@genrad.UUCP>
Date: 6 Jul 90 14:53:53 GMT
Sender: news@genrad.UUCP
Lines: 60


// Weird Borland Turbo C++ BUG! Calls destructor for local object twice!
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>

class Trace
    {
    const char *name;  			// points to the string arg in the code body
    static int spaces;  		// space over this much before printing out trace msg
public:
    Trace(const char *fname);
    ~Trace();
    };

class Foobar
    {
    int k;
public:
    Foobar(int i = 0 ) { k = i; }
    ~Foobar() { Trace trace("~Foobar"); }
    // Note that this destructor causes a Trace object to
    // be created and destroyed.
    };

//----------------------------------------------------------------------------
main()
    {
    Foobar y;  // Borland calls destructor TWICE!
	// This results in zillions of spaces being sent
	// to the output stream from the ~Trace below.
	// Happens on my 286 Clone and on a 386
	// Works fine on Sun C++ 2.0
    }

//---------------------------------------------------------------------------------
Trace::Trace(const char *p)
    {
    name = p;
    int i = spaces;
    spaces+=2;
    while ( i-- )
	cout << " ";
    cout << "enter " << p << '\n';
    }

Trace::~Trace()
    {
    spaces-=2;
    int i = spaces;
    while ( i-- )
	cout << " ";
    cout << "leave " << name << '\n';
    }
// Many thanks to Craig Dawson at GenRad for confirming this bug
// on his 386 PC. Extensive analysis with the Turbo debugger
// whittled this down from a much larger program to what you see
// above.
// Charlie Havener at GenRad Inc. 300 Baker Ave. Concord. Mass.
// charlie@genrad.com