[ECOS] Re: Some weirdnes with the tools

[Jesper Skov <jskov@cygnus.co.uk>]

If I'm not mistaken (and I may very well be) the problem is caused
because you use a 'new' operator without defining it. I think it calls
malloc() and throws an exception if the allocation fails. Remember
that C++ exceptions are not handled when you use the default compiler
arguments. 

Anyway, this is beyond me. I'm not the biggest C++ hacker there ever
was, I must admit. You should have asked on the list directly where
you would be more likely to get a correct answer.


Jesper

--------------------
Hi Jesper,
This WE, I came accross something I really do not understand. I am working
on a package implementing the CANopen protocol. I am writing this in C++.

It contains something like this :

class CommunicationObject
{ ...
  public:
    virtual      ~CommunicationObject();
    virtual void create(void) = 0;
    virtual void destroy(void) = 0;
};

class TxCOB : public CommunicationObject
{ ...
  public:
    virtual      ~TxCOB();
    virtual void create(void);
    virtual void destroy(void);
};

class RxCOB : public CommunicationObject
{ ...
  public:
    virtual      ~RxCOB();
    virtual void create();
    virtual void destroy(void);
};

template <class Type>
class CMS_Variable
{
  ....

  protected:
    CommunicationObject * m_cob;
};

template <class Type>
class CMS_ServerVar : public CMS_Variable<Type>
{
  public:
    CMS_ServerVar()
    {
      m_cob = new TxCOB();
      m_cob->create();
    }
};

template <class Type>
class CMS_ClientVar : public CMS_Variable<Type>
{
  public:
    CMS_ServerVar()
    {
      m_cob = new RxCOB();
      m_cob->create();
    }
};

typedef CMS_ServerVar<int> CMS_IntServerVar;
typedef CMS_ClientVar<int> CMS_IntClientVar;

It compiles and links fine, no problem there.


The strange thing is when I use it from the application that is linked
against the ECOS library.

An application like

main()
{
  CMS_IntServerVar server();
  CMS_IntClientVar client();

  return 0;
}

Crashes on the call to m_cob->create(). When I look at the v-table of both
TxCOB and RxCOB, it is partially filled with zeros. (the create function is
a zero, the destroy is not)

If I rewrite the application as follows

main()
{
  TxCOB txcob();
  CommunicationObject * cob = &txcob;
  cob->create()

  CMS_IntServerVar server();
  CMS_IntClientVar client();

  return 0;
}

everything goes fine and the v-tables of both TxCOB and RxCOB are filled in
correctly.
It looks like only classes that are explicitly instantiated outside the ECOS
library have correctly filled in v-tables (although that doesn't make much
sense to me).

Have you ever come accross something like this ?? Or am I doing something
wrong ?? What section are the v-tables stored in anyway (looks like they are
in .rodata, I am not sure though) I use the EcosSWTools that I downloaded
from the web (with the Redhat 6.0 patch)

If you don't know an answer, can you post this on the appropriate discussion
forum please.

Regards,
Bob

------------------------------------------------------------------------
ir. Bob Koninckx
Katholieke Universiteit Leuven
Division Production Engineering,                      tel. +32 16 322535
Machine Design and Automation                         fax. +32 16 322987
Celestijnenlaan 300B                 bob.koninckx@mech.kuleuven.ac.be
B-3001 Leuven Belgium            http://www.mech.kuleuven.ac.be/pma.html
------------------------------------------------------------------------