How to construct vector with given count in boost interprocess and add elements to it

I've started to learn boost interprocess library and I encountered 2 problems so far. The first one is related to construction of vector with passing its size.

shm.construct<MyShmVector>("MyVector")(MAX_INPUT_SIZE, std::make_pair{"not_used", 0.0}, allocInstance);

/usr/include/boost169/boost/container/string.hpp:220:22: error: no matching function for call to 'boost::interprocess::allocator<char, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >::allocator()'
      : Allocator()

so should I pass arguments to the vector in other way ?

The second problem is related to emplace_back function. When I try to add in this way an element to the vector I get an error:

/usr/include/boost169/boost/container/allocator_traits.hpp:415:10: error: no matching function for call to 'std::pair<boost::container::basic_string<char, std::char_traits<char>, boost::interprocess::allocator<char, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > >, double>::pair(std::basic_string<char>, double)'
   {  ::new((void*)p, boost_container_new_t()) T(::boost::forward<Args>(args)...); }
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So once again I did something wrong ?

The code:

#include<boost/interprocess/managed_shared_memory.hpp>
#include<boost/interprocess/containers/vector.hpp>
#include<boost/interprocess/containers/string.hpp>
#include<boost/interprocess/allocators/allocator.hpp>

constexpr int MAX_INPUT_SIZE = 10'000;
namespace bip = boost::interprocess;

class ShmWrapper
{
    using SegmentManagerType = bip::managed_shared_memory::segment_manager;
    using CharAllocator = bip::allocator<char, SegmentManagerType>;
    using MyShmString =  bip::basic_string<char, std::char_traits<char>, CharAllocator>;
    using MyShmPair = std::pair<MyShmString, double>;
    using MyShmPairAllocator = bip::allocator<MyShmPair, SegmentManagerType>;
    using MyShmVector = bip::vector<MyShmPair, MyShmPairAllocator>;
public:
    ShmWrapper()
    {
        bip::shared_memory_object::remove("SHM_SEGMENT");
        bip::managed_shared_memory shm{bip::open_or_create, "SHM_SEGMENT", MAX_INPUT_SIZE * sizeof(MyShmPair) * 4 + sizeof(MyShmVector)};

        MyShmPairAllocator const allocInstance{shm.get_segment_manager()};
        stocks_ = shm.construct<MyShmVector>("MyVector")(MAX_INPUT_SIZE, std::make_pair("not_used", 0.0), allocInstance);

        for (auto index = 1; index < MAX_INPUT_SIZE; ++index)
            stocks_->emplace_back("Item_" + std::to_string(index), 0.0);
    }

private:
    MyShmVector* stocks_;
};

int main()
{
    ShmWrapper shm;
    return 0;
}

I simply don't get the first error when I try out your code:

https://godbolt.org/z/rBBfHe

That's a normal constructor you're using, and it exists in std::vector too, so there's not another way you're supposed to be calling that I know of.

---

I did reproduce the second one. It's complaining that you used the std::string output of std::to_string to write to an argument that is boost::container::basic_string.

boost::container::basic_string is a bit of a C++98 relic. According to the documentation it, like a lot of 3rd party "better string" implementations, was made to avoid the copy-on-write semantics in gcc's std::string and add some performance optimizations.

Since C++11 bans copy-on-write and mandates short-string optimization, there's few reasons not to use std::string. Just change this line:

using MyShmString =  bip::basic_string<char, std::char_traits<char>, CharAllocator>;

to this:

using MyShmString = std::string

And it should compile.