[ECOS] Re: Some weirdnes with the tools

[ECOS] Re: Some weirdnes with the tools

[Jesper Skov]

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

[ECOS] RE: Some weirdnes with the tools

[Jesper Skov]

>>>>> "Bob" == Bob Koninckx <bob.koninckx@mail.mech.kuleuven.ac.be> writes:

Bob> No, That's certainly not the problem, memory allocation works
Bob> fine. It looks more like a problem that occured with the ARM
Bob> toolchain (The last one on the known problem list)

[please remember to CC the ecos-discuss list]

Come to think of it,we may have seen this, or a similar, problem
before. Try removing the -fvtable-gc option.

Jesper

RE: [ECOS] Re: Some weirdnes with the tools

[Gary Thomas]

I think the problem here is that the 'm_cob->create()' function is declared 
"virtual". There is a known problem with this with our use of --gc-sections 
in the linker.  If the "create" function is only ever referenced as a virtual
function of the class, the linker can't tell that it is being used and
it will blissfully optimize it out of the resulting application.

For the time being a work-around is to remove '-fvtable-gc' from your
compile-time flags.  This will preserve your virtual functions.

On 18-Oct-99 Jesper Skov wrote:
> 
> 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
> ------------------------------------------------------------------------
> 
> 
>