iterator problem

[Chameleon]

All these happen in VC++ NET 2003, if you ask me about the compiler.
it._Myptr is a VC++ specific member of the iterator implementation.
But from this, we extract usefull informations about crash.
----------------------------
vector<int*> v;
vector<int*>::i terator it = v.begin(); // it._Myptr == 0 (what pointer
is this?)
v.insert(it, 5); // works
it++; // it._Myptr == 4
v.insert(it, 5); // crashes
----------------------------
and this.
----------------------------
vector<int*> v;
vector<int*>::i terator it = v.begin(); // it._Myptr == 0
v.push_back(5);
vector<int*>::i terator it = v.begin(); // it._Myptr == 0x00323b40 (the
pointer to first element)
----------------------------


All of these are compiler bugs on iterator implementation, or I miss
something?

Thanks

[Kai-Uwe Bux]

Re: iterator problem

Chameleon wrote:
[color=blue]
> All these happen in VC++ NET 2003, if you ask me about the compiler.
> it._Myptr is a VC++ specific member of the iterator implementation.
> But from this, we extract usefull informations about crash.
> ----------------------------
> vector<int*> v;
> vector<int*>::i terator it = v.begin();
> // it._Myptr == 0 (what pointer is this?)
> v.insert(it, 5); // works[/color]

This insert() call invalidates all iterators to v. In particular:
[color=blue]
> it++; // it._Myptr == 4[/color]

is undefined behavior,
[color=blue]
> v.insert(it, 5); // crashes[/color]

which manifests itself here.
[color=blue]
> ----------------------------
> and this.
> ----------------------------
> vector<int*> v;
> vector<int*>::i terator it = v.begin(); // it._Myptr == 0
> v.push_back(5);[/color]

Do you think that 5 is a good int* ?
[color=blue]
> vector<int*>::i terator it = v.begin(); // it._Myptr == 0x00323b40 (the
> pointer to first element)
> ----------------------------[/color]

What about it?

[color=blue]
> All of these are compiler bugs on iterator implementation, or I miss
> something?[/color]

You missed the rules for iterators for std::vector.



Best

Kai-Uwe Bux

[Chameleon]

Re: iterator problem

Kai-Uwe Bux wrote:[color=blue]
> Chameleon wrote:
>[color=green]
>> All these happen in VC++ NET 2003, if you ask me about the compiler.
>> it._Myptr is a VC++ specific member of the iterator implementation.
>> But from this, we extract usefull informations about crash.
>> ----------------------------
>> vector<int*> v;
>> vector<int*>::i terator it = v.begin();
>> // it._Myptr == 0 (what pointer is this?)
>> v.insert(it, 5); // works[/color]
>
> This insert() call invalidates all iterators to v. In particular:
>[color=green]
>> it++; // it._Myptr == 4[/color]
>
> is undefined behavior,
>[color=green]
>> v.insert(it, 5); // crashes[/color]
>
> which manifests itself here.
>[color=green]
>> ----------------------------
>> and this.
>> ----------------------------
>> vector<int*> v;
>> vector<int*>::i terator it = v.begin(); // it._Myptr == 0
>> v.push_back(5);[/color]
>
> Do you think that 5 is a good int* ?[/color]


sorry, it is a fast-written sample:
vector<int> v;