Re: Problem understanding 'boost::intrusive::list_member_hook<>'

From: Joaquin M López Muñoz (joaquinlopezmunoz_at_[hidden])
Date: 2021-09-09 15:48:21

El 09/09/2021 a las 15:21, John Emmas escribió:
> On 09/09/2021 12:16, Joaquin M López Muñoz via Boost-users wrote:
>> [...]
>> if you mean for the elements to be allowed in both lists at the same 
>> time, use tags:
>>
>> Â Â Â  #include <boost/intrusive/list.hpp>
>> Â Â Â  #include <string>
>> Â Â Â  #include <utility>
>>
>> Â Â Â  typedef 
>> boost::intrusive::list_base_hook<boost::intrusive::tag<struct 
>> animal_tag>> animals_hook;
>> Â Â Â  typedef 
>> boost::intrusive::list_base_hook<boost::intrusive::tag<struct 
>> dog_tag>> dogs_hook;
>>
>> Â Â Â  class animal :
>> Â Â Â Â Â  public animals_hook, public dogs_hook
>> Â Â Â  {
>> Â Â Â Â  public:
>> Â Â Â Â Â Â Â  animal (std::string n, int l) : name{std::move(n)}, legs{l} {}
>>
>> Â Â Â Â Â Â Â  std::string name;
>> Â Â Â Â Â Â Â  int legs;
>> Â Â Â  };
>>
>> Â Â Â  typedef 
>> boost::intrusive::list<animal,boost::intrusive::base_hook<animals_hook>> 
>> Animals;
>> Â Â Â  typedef 
>> boost::intrusive::list<animal,boost::intrusive::base_hook<dogs_hook>> 
>> Dogs;
>>
>> Â Â Â  int main()
>> Â Â Â  {
>> Â Â Â Â Â Â Â  animal a1{"labrador", 4};
>> Â Â Â Â Â Â Â  animal a2{"bulldog", 4};
>>
>> Â Â Â Â Â Â Â  Animals animals;
>> Â Â Â Â Â Â Â  animals.push_back (a2);Â  // <--- 'bulldog' works okay
>>
>> Â Â Â Â Â Â Â  Dogs dogs;
>> Â Â Â Â Â Â Â  dogs.push_back (a1);Â Â Â Â  // <--- 'labrador' works okay
>> Â Â Â Â Â Â Â  dogs.push_back (a2);Â Â Â Â  // <--- 'bulldog' works okay
>>
>> Â Â Â Â Â Â Â  return 0;
>> Â Â Â  }
> [portion above moved from end of post]

Please don't top post. Thank you!

https://www.boost.org/community/policy.html

> Thanks Joaquin - one quick question... do I need to define 'struct 
> animal_tag' and 'struct dog_tag' somewhere?

No, this is not needed.

> At present, your code compiles and links okay but I still see a 
> runtime crash at the same line ('dogs.push_back (a2);')

It seems to work for me:

http://coliru.stacked-crooked.com/a/d605f0b3bccfe9fa

Please note that dogs in line 29 is defined as:

 Â Â Â  Dogs dogs;

whereas in your original code this was:

 Â Â  Animals dogs;

Maybe this is the problem?

Joaquín M López Muñoz