El 09/09/2021 a las 11:28, John Emmas via Boost-users escribió:
On 08/09/2021 15:56, John Emmas wrote:
I realise there are two types of hook available for
'boost::intrusive::list' ( the list_member_hook<> and the
list_base_hook<>) - so are there certain situations where one would
preferable over the other?
Overnight I got told (off-list) that when 2 x classes are both
declared using the 'list_base_hook<>' option, I'll get a runtime crash
if I try to add the same object to both lists. In other words, this
will crash at the specified line:-
class animal : public boost::intrusive::list_base_hook<>
{
[...]
};
[...]
animals.push_back (a2); // <--- 'bulldog' works okay
[...]
dogs.push_back (a2); // <--- 'bulldog' crashes !!!
You're trying to insert a2 into dogs when the element is alredy inserted
into animals.
You can either remove a2 from animals beforehand:
animals.erase(Animals::s_iterator_to(a2));
or, if you mean for the elements to be allowed in both lists at the same
time, use tags:
#include <boost/intrusive/list.hpp>
#include <string>
#include <utility>
typedef
boost::intrusive::list_base_hook<boost::intrusive::tag<struct
animal_tag>> animals_hook;
typedef
boost::intrusive::list_base_hook<boost::intrusive::tag<struct dog_tag>>
dogs_hook;
class animal :
public animals_hook, public dogs_hook
{
public:
animal (std::string n, int l) : name{std::move(n)}, legs{l} {}
std::string name;
int legs;
};
typedef
boost::intrusive::list<animal,boost::intrusive::base_hook<animals_hook>>
Animals;
typedef
boost::intrusive::list<animal,boost::intrusive::base_hook<dogs_hook>> Dogs;
int main()
{
animal a1{"labrador", 4};
animal a2{"bulldog", 4};
Animals animals;
animals.push_back (a2); // <--- 'bulldog' works okay
Dogs dogs;
dogs.push_back (a1); // <--- 'labrador' works okay
dogs.push_back (a2); // <--- 'bulldog' works okay
return 0;
}
Joaquín M López Muñoz
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