["Paul Price" <slxzz@cc.usu.edu>: unsubscribe]

[Paul Morris <pmorris at ptolemy dot arc dot nasa dot gov>]

My gnats report (entered through the web page) seems to have been
misdirected?

                ---------------

Reply-To: <paul@xpit.com>
From: "Paul Price" <slxzz@cc.usu.edu>
To: <pmorris@ptolemy.arc.nasa.gov>
Subject: unsubscribe
Date: Fri, 26 May 2000 17:48:26 -0700



-----Original Message-----
From: gnats-prs-owner@sourceware.cygnus.com
[mailto:gnats-prs-owner@sourceware.cygnus.com]On Behalf Of
pmorris@ptolemy.arc.nasa.gov
Sent: Friday, May 26, 2000 3:28 PM
To: gnats-gnats@sourceware.cygnus.com
Cc: wedgingt@ptolemy.arc.nasa.gov
Subject: gnats/78: g++ 2.95.2 copies without constructor, then calls
destructor



>Number:         78
>Category:       gnats
>Synopsis:       g++ 2.95.2 copies without constructor, then calls
destructor
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 26 15:34:00 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator:     Paul Morris and Will Edgington
>Release:        g++-2.95.2 and earlier
>Organization:
>Environment:
Sun Ultra 2 SunOS 5.6 (Solaris)
>Description:
g++ compiles incorrectly.  Under certain circumstances, it
creates a copy without calling the copy constructor, and
later passes the copy to the destructor.  This can cause
reference-count schemes to prematurely release storage.
>How-To-Repeat:
Enclosed is a self-contained program that exercises the bug,
with print statements to illustrate the problem.
Note that the refCount goes to -1.(If the SUNWspro compiler
is used instead, the refCount correctly ends at 0.)

PRINTOUT FROM EXAMPLE PROGRAM

Created tag 1 item
     refCount now 1
Created tag 2 item as copy of tag 1 item
     refCount now 2
Created tag 3 item
Assigned tag 3 item as copy of tag 2 item
     refCount now 3
Descoped tag 2 item
     refCount now 2
Created tag 4 item as copy of tag 3 item
     refCount now 3
Created tag 5 item
Assigned tag 5 item as copy of tag 4 impostor
     refCount now 4
Descoped tag 4 impostor
     refCount now 3
Descoped tag 4 item
     refCount now 2
Descoped tag 5 item
     refCount now 1
Descoped tag 3 item
     refCount now 0
Descoped tag 1 item
     refCount now -1
>Fix:
The compiler needs to be modified to call the copy
constructor when it makes the copy identified as the
"impostor" in the example printout.
>Release-Note:
>Audit-Trail:
>Unformatted:

----gnatsweb-attachment----
Content-Type: application/octet-stream; name="test.cc"
Content-Transfer-Encoding: text
Content-Disposition: attachment; filename="test.cc"

#include <iostream.h>

class ModId {
public:
  ModId (int datum = 0);
  ModId(const ModId& org);
  ModId& operator=(const ModId& org);
  ~ModId ();
  char* judge() const;
private:
  int tag;
  int datum;
  int* refCount;
};

int topTag = 1;
ModId* tagPtr[1000];

char* ModId::judge() const 
{ return (this == tagPtr[this->tag]) ? " item " : " impostor "; }

ModId::ModId (int dat)
{
  tagPtr[tag = topTag++] = this;
  datum = dat;
  *(refCount = new int) = 1;

  cerr << "Created tag " << tag << judge() << "\n";
  if (datum) cerr << "     refCount now " << *refCount << "\n";
}

ModId::ModId(const ModId& org)
{
  tagPtr[tag = topTag++] = this;
  datum = org.datum;
  (*(refCount = org.refCount))++;

  cerr << "Created tag " << tag << judge() << "as copy of tag " << org.tag
       << org.judge() << "\n";
  if (datum) cerr << "     refCount now " << *refCount << "\n";
}

ModId::~ModId ()
{
  (*refCount)--;

  cerr << "Descoped tag " << tag << judge() << "\n";
  if (datum) cerr << "     refCount now " << *refCount << "\n";
}

ModId& ModId::operator=(const ModId& org)
{
  (*org.refCount)++;
  (*refCount)--;

  cerr << "Assigned tag " << tag << judge() << "as copy of tag " << org.tag
       << org.judge() << "\n";
  if (datum && org.datum)
    cerr << "     refCount unchanged" << *refCount << "\n";
  else if (datum) cerr << "     refCount now " << *refCount << "\n";
  else if (org.datum) cerr << "     refCount now " << *(org.refCount) << "\n";

  refCount = org.refCount;
  datum = org.datum;
  // Tag itself not copied -- unique to each instance

  return *this;
}

class VarEntry {
public:
  ModId mod;
  VarEntry (ModId p) { mod = p; }
  VarEntry () { }
};

class pseudoTT {
  ModId mod;
public:
  pseudoTT (ModId p) { mod = p; }
  pseudoTT () { }
};

VarEntry copy (const VarEntry& var) { return var; }

int main()
{
  ModId foo(1);
  VarEntry v(foo);
  pseudoTT var = pseudoTT(copy(v).mod);
}