boost json serialization and message_queue segfault - c++

Question

i'm making some test with boost interprocess and ptree structure, i have a segfault when i try to read the message sent(or when i try to parse it in json).
i'm using boost1.49 on debian linux.
i'm serializing it in json for later uses, and because i didn't find any good doc for the direct serialization of the boost property threes.
this is the code i'm using to test(the commed say where the segfault is):
recv.cc
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/interprocess/ipc/message_queue.hpp>
#include <sstream>
struct test_data{
std::string action;
std::string name;
int faceID;
uint32_t Flags;
uint32_t freshness;
};
test_data recvData()
{
boost::interprocess::message_queue::remove("queue");
boost::property_tree::ptree pt;
test_data data;
std::istringstream buffer;
boost::interprocess::message_queue mq(boost::interprocess::open_or_create,"queue", 1, sizeof(buffer)
boost::interprocess::message_queue::size_type recvd_size;
unsigned int pri;
mq.receive(&buffer,sizeof(buffer),recvd_size,pri);
std::cout << buffer.str() << std::endl; //the segfault is there
boost::property_tree::read_json(buffer,pt);
data.action = pt.get<std::string>("action");
data.name = pt.get<std::string>("name");
data.faceID = pt.get<int>("face");
data.Flags = pt.get<uint32_t>("flags");
data.freshness = pt.get<uint32_t>("freshness");
boost::interprocess::message_queue::remove("queue");
return data;
}
int main()
{
test_data test;
test = recvData();
std::cout << test.action << test.name << test.faceID << test.Flags << test.freshness << std::endl;
}
sender.cc
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/interprocess/ipc/message_queue.hpp>
#include <sstream>
struct test_data{
std::string action;
std::string name;
int faceID;
uint32_t Flags;
uint32_t freshness;
};
int sendData(test_data data)
{
boost::property_tree::ptree pt;
pt.put("action",data.action);
pt.put("name",data.name);
pt.put("face",data.faceID);
pt.put("flags",data.Flags);
pt.put("freshness",data.freshness);
std::ostringstream buffer;
boost::property_tree::write_json(buffer,pt,false);
boost::interprocess::message_queue mq(boost::interprocess::open_only,"chiappen")
std::cout << sizeof(buffer) << std::endl;
mq.send(&buffer,sizeof(buffer),0);
return 0;
}
int main ()
{
test_data prova;
prova.action = "registration";
prova.name = "prefix";
prova.Flags = 0;
prova.freshness = 52;
sendData(prova);
}

Answer 1

I know it's a bit late to an answer right now, but anyway..
You can't pass an istringstream as a buffer for receive. Boost message queues only handle raw bytes and don't handle std like objects.
To make it work, you must use a char array or any buffer previously reserved with malloc.
Ex:
char buffer [1024];
mq.receive(buffer, sizeof(buffer), recvd_size, pri);
For sending it's the same, you can only send raw bytes, so you can't use ostringstream.
Hope it helps.