boost - unordered_map with string in managed_shared_memory fails -

this code:

int main (int argc, char *argv[]) {     typedef int keytype;     typedef string mappedtype;      typedef std::pair<keytype, mappedtype> valuetype;     typedef boost::interprocess::allocator<valuetype, boost::interprocess::managed_shared_memory::segment_manager> shmalloc;     typedef boost::unordered_map<keytype, mappedtype, boost::hash<keytype>, std::equal_to<keytype>, shmalloc> shmhashmap;      boost::interprocess::managed_shared_memory segment(boost::interprocess::open_or_create, "containersharedmemory", 65536);      if(argc == 2 && string(argv[1]) == "clear")     {         boost::interprocess::shared_memory_object::remove("containersharedmemory");         return 0;     }      shmhashmap *hash_map = segment.find_or_construct<shmhashmap>(boost::interprocess::unique_instance)(segment.get_segment_manager());      if(hash_map == null)     {         cout << "find_or_construct error" << endl;         return 0;     }      for(int = 0; < 5; ++i) {         shmhashmap::iterator iter = hash_map->find(i);         if (iter == hash_map->end()) {             hash_map->insert(valuetype(i, "test"));         }     }      cout << "all..." << endl;     for(shmhashmap::iterator iter = hash_map->begin(); iter != hash_map->end(); ++iter)     {         cout << iter->first << "|" << iter->second << endl;     }     cout << "end..." << endl;      return 0; } 

everything ok when mappedtype int, segment fault whit code this:

rerun program access hash map in shared memory coredump

----------------------------edit again----------------------------------

the problem string solved sehe, thank , if design template class want hide detail, how do? if there perfect way

template<typename mappedtype> struct complexmappedtype {     complexmappedtype(): t_access(0), t_expire(0) {}     complexmappedtype(const mappedtype& v, uint32_t a, uint32_t e): value(v), t_access(a), t_expire(e) {}     mappedtype value;      uint32_t t_access;      uint32_t t_expire;  };   template <typename keytype, typename mappedtype>  class mmshashmap  {  private:     typedef complexmappedtype<mappedtype> datatype;     typedef std::pair<keytype, datatype> valuetype;     typedef boost::interprocess::allocator<valuetype, boost::interprocess::managed_shared_memory::segment_manager> shmalloc;     typedef boost::unordered_map<keytype, datatype, boost::hash<keytype>, std::equal_to<keytype>, shmalloc> shmhashmap;  public:     mmshashmap(const std::string& name, size_t size, float e_thr, float e_scale);     ~mmshashmap() {delete pmemorysegment;}      size_t getmemsize() { return pmemorysegment->get_size(); }     size_t getmemfreesize() { return pmemorysegment->get_free_memory(); }      bool get(const keytype& key, mappedtype& value, uint32_t& expire);     bool set(const keytype& key, const mappedtype& value, uint32_t expire);     bool del(const keytype& key);  private:     void docapacityelimination();      std::string _name;     boost::interprocess::managed_shared_memory* pmemorysegment;     boost::shared_mutex mutex, mutex_eliminate;     float feliminatethreshold, feliminatescale; }; 

of course. std::string allocates heap.

the heap in process address space, other process reading same shared memory going wrong raw pointer there , invoke ub.

you need use shared-memory allocator strings too.

live on coliru (using mapped file coliru)

with shared memory:

#include <boost/interprocess/managed_shared_memory.hpp> #include <boost/interprocess/allocators/allocator.hpp> #include <boost/container/scoped_allocator.hpp> #include <boost/container/string.hpp> #include <boost/unordered_map.hpp> #include <iostream>  namespace bip = boost::interprocess;  int main (int argc, char *argv[]) {     typedef int keytype;      typedef boost::container::basic_string<char, std::char_traits<char>, bip::allocator<char, bip::managed_shared_memory::segment_manager> > mappedtype;      typedef std::pair<keytype, mappedtype> valuetype;     typedef boost::interprocess::allocator<valuetype, boost::interprocess::managed_shared_memory::segment_manager> shmalloc;     typedef boost::unordered_map<keytype, mappedtype, boost::hash<keytype>, std::equal_to<keytype>, boost::container::scoped_allocator_adaptor<shmalloc> > shmhashmap;      boost::interprocess::managed_shared_memory segment(boost::interprocess::open_or_create, "containersharedmemory", 65536);      if(argc == 2 && std::string(argv[1]) == "clear")     {         boost::interprocess::shared_memory_object::remove("containersharedmemory");         return 0;     }      shmhashmap *hash_map = segment.find_or_construct<shmhashmap>(boost::interprocess::unique_instance)(segment.get_segment_manager());      if(hash_map == null)     {         std::cout << "find_or_construct error" << std::endl;         return 0;     }      for(int = 0; < 5; ++i) {         shmhashmap::iterator iter = hash_map->find(i);         if (iter == hash_map->end()) {             hash_map->insert(valuetype(i, mappedtype { "hello", segment.get_segment_manager() }));         }     }      std::cout << "all..." << std::endl;     for(shmhashmap::iterator iter = hash_map->begin(); iter != hash_map->end(); ++iter)     {         std::cout << iter->first << "|" << iter->second << std::endl;     }     std::cout << "end..." << std::endl; } 

prints

all... 4|hello 3|hello 2|hello 1|hello 0|hello end...