Re: heap corruption problem in singleton class

From:

Paavo Helde <myfirstname@osa.pri.ee>

Newsgroups:

comp.lang.c++

Date:

Mon, 21 Feb 2011 11:51:13 -0600

Message-ID:

<Xns9E93C9F6718A4myfirstnameosapriee@216.196.109.131>

"venkatarao0@gmail.com" <battula.venkat@gmail.com> wrote in
news:d7cfd4e4-3381-43e0-910a-27461a85e8b2@t13g2000prc.googlegroups.com:

Hi all,

Here one tricky issue, In my project I have used a singleton class
used to store data and value info. this information I will use(call
after system up) 4 times in a year and depends on the requirement not
frequently. In rare scenario while calling get member function I am
getting the exception my system is going down(core dump). I
reproduced the issue bye corrupting the ms_ptr pointer pointing to the
memory location(in Vxworks 6.7 facility is there) bye manually after
some time(not immediately) I generated a scenario to call this
singleton class member function I got the same core dump.

What do you mean? The core dump file was byte-by-byte identical to the
first core dump file?

This same
issue I reproduced by ms_ptr pointing to invalid location.

class config_data
{
  public:
    typedef config_data this_t;
    typedef map<char*, int> input_data;

Using 'char*' here seems error-prone, suggesting std::string instead.

      static this_t& instance ();

    void set (const input_data& inData);
  private:
     static this_t* ms_ptr;
    // Constructor
    config_data () {}
    // GET method
int get (const char *inName, const int inValue);

    // Cannot copy a singleton
    config_data(const this_t&);
    this_t& operator= (const this_t&);
};

config_data* config_data::ms_ptr(NULL);
config_data& config_data::instance ()
{
    if (!ms_ptr)
    {
ms_ptr = new config_data;
    }
    return *ms_ptr;
}
set & get used to set the values into map and getting the values from
map. there is iterator problem over here I have not used iterator in
get also.

If yoy think the error appeared in the get() method it would have been
wise to include its definition, and maybe also an example of how you call
it.

can any one please help me to fix this problem.

1) I want to know who is corrupting the heap location fist to fix the
problem. How I come to know while corrupting the heap memory itself
there is any mechanism to protect/ raise an exception while corrupting
the memory itself.

Run your code with valgrind, this is a good tool for finding out memory
access errors.

hth
Paavo