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Errors when deleting dynamic memory stored within std::map [solved]

Started by eSCHEn Mar 25, 2006 at 8:43 PM 4 replies 1.4k views

Original Post

Mar 25, 2006 at 8:43 PM

Hi, I'm using a std::map to contain some dynamically allocated classes within C++. The classes are constructed in the main loop and then added to a std::map, which is then responsible for them. Everything works hunky-dory until I come to clear out the map, when I get nasty errors galore. Here's a link to the error in question: clicky (9Kb). Here's an example of how I'm declaring and using the std::map:

// definition of map type
typedef std::map<std::string, gui::CForm*> TStringFormMap;

// this is how I add a form
bool CApplication::AddForm(gui::CForm* Form)
{
    // error checking
    if (Form == NULL)
        return false;
    if (Form->GetName() == "")
        return false;
    if (m_forms.find(Form->GetName()) != m_forms.end())
        return false;

    // add form
    m_forms[Form->GetName()] = Form;
    return true;
}

// this is how I delete a form
void CApplication::DeleteForm(const std::string FormName)
{
    if (this->Forms(FormName) != NULL)
    {
        if (FormName == m_focused_form)
            m_focused_form.clear();
        gui::CForm* form_del = m_forms[FormName];
        delete form_del;
        form_del = NULL;
        m_forms.erase(FormName);
    }
}


// sample usage
gui::CForm form1;
g_application.AddForm(&form1);
// blah...
// kill form
g_application.DeleteForm(form1.GetName());  // bang!

The "DeleteForm" line at the bottom is what generates the error in question. Many thanks. [Edited by - eSCHEn on March 25, 2006 9:18:02 PM]

dave

Mar 25, 2006 at 8:47 PM

Hey bud,

The first thing to check is that the form name you are deleting actually exists. there is no checking for this in the deleting function.

That's all i can think of i'm afraid, hope that helps,

Dave

eSCHEn

Mar 25, 2006 at 8:52 PM

Hi Dave, thanks for the suggestion but unfortunately I already check for a form's existence using this->Forms("") which returns NULL if the form doesn't exist within the map.

Thanks for trying though [smile].

graveyard filla

Mar 25, 2006 at 8:58 PM

hmmm

it looks like you are creating a Form on the stack, and then trying to delete it....

this is no good!

this:
gui::CForm form1;
g_application.AddForm(&form1);

needs to become this:
gui::CForm *form1 = new gui::CForm();
g_application.AddForm(form1);

you cannot delete memory you didn't allocate yourself.... why are you even using pointers if you are going to create it on the stack?

PS, you can consolidate the following 3 lines:

gui::CForm* form_del = m_forms[FormName];
delete form_del;
form_del = NULL;

into this:

delete m_forms[FormName];

eSCHEn

Mar 25, 2006 at 9:15 PM

I love you forever man, you just sorted it [grin]. Thanks a lot for the code suggestion as well, always appreciated!

If you're ever in SW Scotland then you're more than welcome to come in for a nice cup of tea and some biscuits :)

Rating++ for you my good sir.

graveyard filla

Mar 25, 2006 at 9:26 PM

your welcome [grin]

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