I'm trying to allocate a string inside a custom object SharedValue in shared memory using Boost 1.73.0
My object:
typedef boost::interprocess::allocator<char, boost::interprocess::managed_shared_memory::segment_manager> char_allocator;
class SharedValue {
public:
SharedValue(const char_allocator& ca);
boost::interprocess::basic_string<char, std::char_traits<char>, char_allocator> val;
};
SharedValue::SharedValue(const char_allocator& ca) : val(ca) {}
Then in the shared memory builder:
boost::interprocess::managed_shared_memory shm(boost::interprocess::open_or_create, "SharedMemory", 65536);
boost::interprocess::managed_shared_memory::allocator<char>::type ca(shm.get_allocator<char>());
auto *value = shm.find_or_construct<SharedValue>(string(ID + "_" + name + "_SharedValueSHM").c_str())(ca);
And it gives me this error:
In file included from boost/include/boost/interprocess/containers/string.hpp:23,
from SharedValue.h:24,
from SharedValue.cpp:13:
boost/include/boost/container/string.hpp: In instantiation of ‘boost::container::dtl::basic_string_base<Allocator>::members_holder::members_holder() [with Allocator = boost::interprocess::allocator<char, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >]’:
boost/include/boost/container/string.hpp:100:18: required from ‘boost::container::dtl::basic_string_base<Allocator>::basic_string_base() [with Allocator = boost::interprocess::allocator<char, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >]’
boost/include/boost/container/string.hpp:643:16: required from ‘boost::container::basic_string<CharT, Traits, Allocator>::basic_string() [with CharT = char; Traits = std::char_traits<char>; Allocator = boost::interprocess::allocator<char, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >]’
SharedValue.cpp:19:50: required from here
boost/include/boost/container/string.hpp:220:27: 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()’
220 | : allocator_type()
| ^
In file included from boost/include/boost/interprocess/segment_manager.hpp:38,
from boost/include/boost/interprocess/detail/managed_memory_impl.hpp:30,
from boost/include/boost/interprocess/managed_shared_memory.hpp:25,
from SharedValue.h:21,
from SharedValue.cpp:13:
boost/include/boost/interprocess/allocators/allocator.hpp:142:4: note: candidate: ‘template<class T2> boost::interprocess::allocator<T, SegmentManager>::allocator(const boost::interprocess::allocator<T2, SegmentManager>&)’
142 | allocator(const allocator<T2, SegmentManager> &other)
| ^~~~~~~~~
boost/include/boost/interprocess/allocators/allocator.hpp:142:4: note: template argument deduction/substitution failed:
In file included from boost/include/boost/interprocess/containers/string.hpp:23,
from SharedValue.h:24,
from SharedValue.cpp:13:
boost/include/boost/container/string.hpp:220:27: note: candidate expects 1 argument, 0 provided
220 | : allocator_type()
| ^
In file included from boost/include/boost/interprocess/segment_manager.hpp:38,
from boost/include/boost/interprocess/detail/managed_memory_impl.hpp:30,
from boost/include/boost/interprocess/managed_shared_memory.hpp:25,
from SharedValue.h:21,
from SharedValue.cpp:13:
boost/include/boost/interprocess/allocators/allocator.hpp:136:4: note: candidate: ‘boost::interprocess::allocator<T, SegmentManager>::allocator(const boost::interprocess::allocator<T, SegmentManager>&) [with T = char; SegmentManager = boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index>]’
136 | allocator(const allocator &other)
| ^~~~~~~~~
boost/include/boost/interprocess/allocators/allocator.hpp:136:4: note: candidate expects 1 argument, 0 provided
boost/include/boost/interprocess/allocators/allocator.hpp:131:4: note: candidate: ‘boost::interprocess::allocator<T, SegmentManager>::allocator(boost::interprocess::allocator<T, SegmentManager>::segment_manager*) [with T = char; SegmentManager = boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index>; boost::interprocess::allocator<T, SegmentManager>::segment_manager = boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index>]’
131 | allocator(segment_manager *segment_mngr)
| ^~~~~~~~~
boost/include/boost/interprocess/allocators/allocator.hpp:131:4: note: candidate expects 1 argument, 0 provided
Anyone have some ideas to solve this error?
Thanks
It compiles fine for me on 1_73_0:
I would probably not write it like that, but slightly briefer:
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
namespace bip = boost::interprocess;
namespace Shared {
using Mem = bip::managed_shared_memory;
template <typename T>
using Alloc = bip::allocator<T, Mem::segment_manager>;
using String
= bip::basic_string<char, std::char_traits<char>, Alloc<char> >;
struct Value {
Value(String::allocator_type a)
: val(a) { }
String val;
};
}
int main()
{
using namespace Shared;
Mem shm(bip::open_or_create, "SharedMemory", 65536);
auto* value = shm.find_or_construct<Value>(
"ID_name_SharedValueSHM")(shm.get_segment_manager());
}
This would sidestep the apparent type mismatch between youd
char_allocator
and the result ofboost::interprocess::managed_shared_memory::allocator<char>::type
. Really, you should probably check that it is using the correctly spelled typedefs in your real code.
Leveraging the implicit construction of the allocator from a segment manager pointer. If you can, accept heterogeneous allocators, because they can interconvert:
template <typename Alloc>
explicit Value(Alloc a) : val(a) { }
This will help when you get more advanced and use e.g. scoped allocators.