SIGABRT on dump()

[cronnosli]

/usr/local/include/nlohmann/json.hpp:6190: void nlohmann::detail::serializer::dump(const BasicJsonType&, bool, bool, unsigned int, unsigned int) [with BasicJsonType = nlohmann::basic_json<>]: Assertion `std::next(i) == val.m_value.object->cend()' failed.

Thread 1 "pk052" received signal SIGABRT, Aborted

[nlohmann]

Could you please provide more information: how does your JSON value look like? Which version of the code you are using? Which OS/compiler?

[cronnosli]

I'm compiling into an armhf raspberry pi 3 using raspbian 9 and g++ 6.3.
The error occurs randomly.

The data looks like:
{"assembled":500,"meta":870,"currTarget":515,"station":[{"name":"1","value":0},{"name":"10","value":0},{"name":"11","value":0},{"name":"12","value":0},{"name":"2","value":125},{"name":"3","value":0},{"name":"4","value":0},{"name":"5","value":0},{"name":"6","value":0},{"name":"7","value":0},{"name":"8","value":0},{"name":"9","value":0},{"name":"gin","value":0},{"name":"lunch","value":3600},{"name":"cleanning","value":0},{"name":"timeStopped","value":3725}],"tackt":65350}

[nlohmann]

This is really strange. The assertion makes sure we properly iterated over the object.

Here is the code for that:

o->write_character('{');

// first n-1 elements
auto i = val.m_value.object->cbegin();
for (std::size_t cnt = 0; cnt < val.m_value.object->size() - 1; ++cnt, ++i)
{
    o->write_character('\"');
    dump_escaped(i->first, ensure_ascii);
    o->write_characters("\":", 2);
    dump(i->second, false, ensure_ascii, indent_step, current_indent);
    o->write_character(',');
}

// last element
assert(i != val.m_value.object->cend());
assert(std::next(i) == val.m_value.object->cend()); // <-- this assertion fails
o->write_character('\"');
dump_escaped(i->first, ensure_ascii);
o->write_characters("\":", 2);
dump(i->second, false, ensure_ascii, indent_step, current_indent);

o->write_character('}');

The assertion states that iterator i must point to the last element of the object. If the assertion fails, then for some strange reason iterator i does not point to the last element of the object even though we incremented from cbegin() size()-1 times.

I am clueless how you get into a situation where the assertion does not hold.

[cronnosli]

I thought that it could be some sort of problem with shared data between two threads, but even using mutex to protect data writes the result was the same.

Using the lastest release another segmentation fault occurs but with the same dump call.
received signal SIGSEGV, Segmentation fault.
0x0007390c in unsigned int std::accumulate<__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, unsigned int, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long long, unsigned long long, double, std::allocator, nlohmann::adl_serializer>::extra_space(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)::{lambda(unsigned int, char)#1}>(__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, unsigned int, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long long, unsigned long long, double, std::allocator, nlohmann::adl_serializer>::extra_space(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)::{lambda(unsigned int, char)#1}, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long long, unsigned long long, double, std::allocator, nlohmann::adl_serializer>::extra_space(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)::{lambda(unsigned int, char)#1}) ()

[gregmarr]

Can you post the full stack trace, or at least more of it?
Are you using the same json object across multiple threads?
If so, are you sure the mutex is protecting all access (not just all writes)?

[cronnosli]

Yes I'm sure, there is only one thread writting into the json object.

I have a std::thread member function called run, in which the json is been manipulated. There is a std::lock_guard protecting the write.

On the main thread I access a member function called get, that return the std::string from the dump. The read also call a std::lock_guard before the dump.

[cronnosli]

I found new information on this.
I change the logic to share a struct and make sure the problem wasn't within the mutex.

struct MyData {
  uint32_t assembled;
  uint32_t goal;
  uint32_t currentGoal;
  uint32_t tackt;
  uint32_t stops;
  std::map<std::string, uint64_t> station;
};

std::string MyObject::get() {
    std::string data = "";
    json transfer;
    transfer["station"] = json::array();
    try {
        MyData localData;
        {
            std::lock_guard<std::mutex>(this->mutex);
            localData = this->countData;
        }
        transfer["assembled"] = localData.assembled;
        transfer["goal"] = localData.goal;
        transfer["currentGoal"] = localData.currentGoal;
        transfer["stops"] = localData.stops;
        transfer["tackt"] = localData.tackt;
        for (auto station : localData.station) {            
            transfer["station"].push_back({
                {"name", station.first},
                {"value", station.second}
            });
        }
        data = transfer.dump();
    } catch (std::exception &e) {
        std::cout << "Error count get: " << e.what() << std::endl;
    } catch (...) {
        std::cout << "Error count get" << std::endl;
    }
    return data;
}

The problem looks to be here:

transfer["station"].push_back({
        {"name", station.first},
       {"value", station.second}
});

Here is the backtrace:

Thread 1 "counterSystem" received signal SIGSEGV, Segmentation fault.
0x76e62f1c in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
   from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6


# 0  0x76e62f1c in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
   from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
# 1  0x0006cabc in std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>::pair(std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&) ()
# 2  0x000787e8 in void __gnu_cxx::new_allocator<std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::construct<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&>(std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>*, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&) ()
#3  0x00078188 in void std::allocator_traits<std::allocator<std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > > >::construct<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&>(std::allocator<std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >&, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>*, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&) ()
#4  0x00077cb0 in void std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_construct_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >*, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&) ()
#5  0x00077d20 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_create_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&>(std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&) ()
#6  0x00076d88 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node::operator()<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&>(std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> const&) ()
#7  0x00075f68 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_clone_node<std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > const*, std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node&)()
#8  0x000734e8 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_copy<std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > const*, std::_Rb_tree_node_base*, std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node&) ()
#9  0x00073528 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_copy<std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > const*, std::_Rb_tree_node_base*, std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node&) ()
#10 0x00073528 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_copy<std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > const*, std::_Rb_tree_node_base*, std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node&) ()
#11 0x00073528 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_copy<std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > const*, std::_Rb_tree_node_base*, std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node&) ()
#12 0x00073528 in std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >* std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_M_copy<std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node>(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > const*, std::_Rb_tree_node_base*, std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::_Reuse_or_alloc_node&) ()
#13 0x00070568 in std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::operator=(std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > > const&) ()
#14 0x0006d824 in std::map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned long long, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > >::operator=(std::map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned long long, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, unsigned long long> > > const&) ()
#15 0x0006ca60 in MyObject::operator=(MyData const&) ()
#16 0x0006afe0 in MyObject::get[abi:cxx11]() ()
#17 0x00056238 in main ()

The problem is not constant, the software could run for 1 hour before get this segfault.

[gregmarr]

The segfault is actually here:

localData = this->countData;

There is no json anywhere in this stack trace.

Actually, that's not it either. It's in MyObject::operator=(MyData const&), which I don't even see in this function. Are you running with these actual type names, or did you do some text replacement?

[cronnosli]

Ok, so what is affecting this copy was also affecting the access in the json before when it fault into:

/usr/local/include/nlohmann/json.hpp:6190: void nlohmann::detail::serializer::dump(const BasicJsonType&, bool, bool, unsigned int, unsigned int) [with BasicJsonType = nlohmann::basic_json<>]: Assertion `std::next(i) == val.m_value.object->cend()' failed.

Thread 1 "pk052" received signal SIGABRT, Aborted

Right?

[gregmarr]

That one seems like some other thread is modifying the json object during the dump call.

[cronnosli]

But in the previous code I was just interact with the json array in a for loop. And it was protected by a mutex lock.

Could be that the reference for the object was destroyed durring the operation?

[gregmarr]

There really isn't enough information to tell what's going on here. It does seem to be something outside the basic operation of the library.

[nlohmann]

I'm closing this. I shall reopen the issue when we have more information on why this library is causing the SIGABRT.