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Weird (?) problem using std::list ...

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Join Date: Mar 2006

Posts: 4

Reputation: shlinky is an unknown quantity at this point

Solved Threads: 0

shlinky

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Newbie Poster

Weird (?) problem using std::list ...

Mar 23rd, 2006

Hi!

I have a class called anItem which is defined something like this :

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 C++ Syntax (Toggle Plain Text) 
class anItem
{
   CString string1;
   CString string2;
   long bla1;
   long bla2;
}
class anItem
{
   CString string1;
   CString string2;
   long bla1;
   long bla2;
}

ok should be enough. Constructor/Destructor are empty.

At another place I use this class as a template for a std::list.

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C++ Syntax (Toggle Plain Text)

std::list<anItem> list;

I can add and get items from that list without any problem, UNLESS I do the following.

If I add another Item to the anItem-class, it only works if it is not a CString type.

Examples :

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 C++ Syntax (Toggle Plain Text) 
class anItem
{
   CString string1;
   CString string2;
   char string3[10000]; //new char array
   long bla1;
   long bla2;
}
class anItem
{
   CString string1;
   CString string2;
   char string3[10000]; //new char array
   long bla1;
   long bla2;
}

above is OK!

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 C++ Syntax (Toggle Plain Text) 
class anItem
{
   CString string1;
   CString string2;
   CString string3; // new CString
   long bla1;
   long bla2;
}
class anItem
{
   CString string1;
   CString string2;
   CString string3; // new CString
   long bla1;
   long bla2;
}

Runtime Error ("Memory could not be read.").

Does any of you have an idea what the problem here is?
I am using MS Visual C++ 6.0; this is used in an MFC application.

Thanks!

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Join Date: Sep 2004

Posts: 7,625

Reputation: Narue has a reputation beyond repute

Solved Threads: 717

Narue

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Code Goddess

Re: Weird (?) problem using std::list ...

Mar 23rd, 2006

>I have a class called anItem which is defined something like this
I'll assume it's "something" like that rather than exactly like that because that class won't compile (no trailing semicolon) and even if it did would be unusable because all of the data members are private with no way to access them.

>Runtime Error ("Memory could not be read.").
Step through your code, and find out exactly when this happens and what you're doing at the time. Debugging remotely is difficult enough when the problem isn't vague.

I'm here to prove you wrong.

•

Join Date: Mar 2006

Posts: 4

Reputation: shlinky is an unknown quantity at this point

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shlinky

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Newbie Poster

Re: Weird (?) problem using std::list ...

Mar 23rd, 2006

youre right, sorry. here is the actual class :

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class DataTreeItem  
{
public:
	DataTreeItem();
	virtual ~DataTreeItem();
 
CString projectpath;
	CString spec;
	CString name;
	char local[1024];
	//CString lspec;
	int size;
	int type;
	long version;
	long checkedout;
	HTREEITEM treeitem;
	IVSSItem * vssitem;
};
class DataTreeItem  
{
public:
	DataTreeItem();
	virtual ~DataTreeItem();

CString projectpath;
	CString spec;
	CString name;
	char local[1024];
	//CString lspec;
	int size;
	int type;
	long version;
	long checkedout;
	HTREEITEM treeitem;
	IVSSItem * vssitem;
};

so what happens is that the app crashes as soon as i compile with the comment removed and CString lspec is an attribute of the class.

Any Ideas anyone??

•

Join Date: Sep 2004

Posts: 7,625

Reputation: Narue has a reputation beyond repute

Solved Threads: 717

Narue

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Code Goddess

Re: Weird (?) problem using std::list ...

Mar 24th, 2006

>so what happens is that the app crashes
Define 'crash'.

>Any Ideas anyone??
No, because you're still not giving enough information. At this point, post a small program that exhibits the problem so that we can debug it personally rather than play twenty questions with you.

I'm here to prove you wrong.

•

Join Date: Nov 2005

Posts: 251

Reputation: dwks has a spectacular aura about

Solved Threads: 25

dwks

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Posting Whiz in Training

Re: Weird (?) problem using std::list ...

Mar 25th, 2006

So this doesn't run:

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CString bad;
bad[999] = 'a';
CString bad;
bad[999] = 'a';

but this does:

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 C++ Syntax (Toggle Plain Text) 
char good[10000];
good[999] = 'a';
char good[10000];
good[999] = 'a';

It looks like a CString is equivalent to a char*. In that case, you need to allocate memory dynamically for it or use a char array.

Your best bet would be to use a string, from <string>. They automatically resize themselves.

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#include <iostream>
#include <string>
 
int main(void) {
    string name;
 
    std::cout << "Enter your name: ";
    std::cin >> name;
 
    std::cout << "Hello, " << name << '!' << std::endl;
 
    return 0;
}
#include <iostream>
#include <string>

int main(void) {
    string name;

    std::cout << "Enter your name: ";
    std::cin >> name;

    std::cout << "Hello, " << name << '!' << std::endl;

    return 0;
}

dwk

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