BOOST 1.73.0 进程间字符串分配器错误

Question

我正在尝试使用 Boost 1.73.0 在共享内存中的自定义对象 SharedValue 中分配一个字符串

我的对象：

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) {}

然后在共享内存构建器中：

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);

它给了我这个错误：

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

有人有解决这个错误的想法吗？

谢谢

Answer 1

它在 1_73_0 上对我来说编译得很好：

• Live On Wandbox
• 在编译器资源管理器（GCC、MSVC）上直播：https://godbolt.org/z/15TM9c

我可能不会那样写，但稍微简短一点：

#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());
}

这会回避你们之间明显的类型不匹配 char_allocator 和结果 boost::interprocess::managed_shared_memory::allocator<char>::type 。 真的，您可能应该检查它是否使用正确 在您的真实代码中拼写 typedef。

利用来自段管理器指针的分配器的隐式构造。如果可以，请接受异构分配器，因为它们可以相互转换：

template <typename Alloc>
explicit Value(Alloc a) : val(a) { }

这将在您变得更高级并使用例如范围分配器。