Re: Crash in erasing element of a list.
Markus Schoder wrote:
Noah Roberts wrote:
mahajan.vibhor@gmail.com wrote:
I have a list of pointers. e.g
A* a = new A(); // A is a class
stl::list<A*> list_a;
I am inserting object of class in the after allocating memeory thru new
operator.
But when i want to erase all elements from the list. my progam crashes.
I delete element by using a iterator.
A * temp = NULL;
stl::list<A*>::iterator Iter,
stl::list<A*>::iterator IterTemp;
for( Iter = list_a.begin() ; Iter != list_a.end() ; ){
Iter = list_a.begin();
temp = *Iter;
IterTemp = Iter;
Iter++;
list_a.erase(IterTemp);
delete temp;
}
Iter is invalid after the erase.
list erase may only invalidate iterators to the erased element.
I doubt it. Think about what happens:
iterator it = v.begin() + 3;
v.erase(v.begin());
What does it point to now?
Iter
should still be valid. As has been pointed out the code can be
improved but I see no reason why the given code has undefined behavior.
What happens when begin() + 1 == end()?
iterator it = begin();
temp = *it; // ok
iterator tempit = it;
++it; // it == end().
v.erase(tempit); // begin() == end().
delete temp;
end state:
v is empty. it points to begin() + 1. Where is end()? it != end().
Continue the loop...
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