Subj : Re: Linux thread weird problem..
To   : comp.programming.threads
From : ranjeetw
Date : Sun Jul 10 2005 04:34 am

Hi Joe,

Sorry, just forgot to give update. I have solution. Thanks for all the
help.

(I am posting what the solution is, though it is not related to
threads, just in case somebody is interested. Though, initially I
thought, it is synchronization issue.)

The trouble was, I adopted a lazy approach to the compare function for
map where I needed to handle 4 different strings as key. This resulted
in the endless loop when erase was called on the map.

struct  mycomparefunction

{
  bool operator()(const node  s1, const node   s2)
  {
	if (strcmp( s1.source_addr , s2.source_addr ) < 0)
             return true;
        else if (strcmp( s1.dest_addr, s2.dest_addr ) < 0)
               return true ;
        else if (strcmp( s1.msg_id, s2.msg_id ) < 0 )
               return true ;
        else if( strcmp(s1.device_id < s2.device_id) < 0 )
             return true ;
        else
             return false ;
  }

};

Whereas it should have been...

struct  mycomparefunction

{
  bool operator()(const node  s1, const node   s2)
  {
        int result = strcmp( s1.source_addr , s2.source_addr );
	if ( result < 0)
             return true;
        else if (result > 0)
              return false;

        result = strcmp( s1.dest_addr, s2.dest_addr );
        if ( result < 0)
               return true ;
        else if (result > 0)
              return false;

        result = strcmp( s1.msg_id, s2.msg_id );
        if ( result < 0 )
               return true ;
        else if (result > 0)
              return false;
        else if( strcmp(s1.device_id < s2.device_id) < 0 )
             return true ;
        else
             return false ;
  }

};

Thanks again,

HTH somebody,

RS.


Joe Seigh wrote:
> ranjeetw@gmail.com wrote:
> >
> > I have single thread handling this data in std::map. This thread waits
> > on select, and gets notified from other threads through pipe (as
> > mentioned earlier).  Main thread wakes up, and processes requests.
> >
> > I am not creating any other thread. I am not passing any functions for
> > callback. I am not supplying pointers to this std::map structures. This
> > remains a mystery for me, why app should get in endless loop in STL lib
> > only.
> >
>
> The data structure was probably corrupted earlier, not at the point
> you're seeing the problem.   I don't have enough inforation and
> am not familiar enough with STL to know what the problem is.  One
> problem is that "threadsafe as int" in C++ doesn't mean very much.
>
>
> --
> Joe Seigh
>
> When you get lemons, you make lemonade.
> When you get hardware, you make software.

.