The problem is you are storing pointers in the map, which are not in
the address space of proc#2. Check
http://ice.prohosting.com/newfunk/boost/libs/shmem/doc/html/shmem/limitation...
On 8/1/06, Pataki Szilard
Hello,
I have a problem retrieving objects from a map placed in shared memory. I have two processes:
proc#1: creates the shared memory, puts a map into it and populates it with objects proc#2: connects to the shared memory and tries to read out the objects from the map
Whenever I try to read out the objects from the map, I get zeroes for the internal members (a, b).
The class definition for the objects: -------------------------------------------------- class ShmNode { private: int a; int b; public: ShmNode(); ShmNode(int newa, int newb); ~ShmNode(); void set(int newa, int newb); int getA(); int getB(); }; --------------------------------------------------
I'm posting the source codes for the two programs. I removed the synchronization stuff with semaphores for the sake of clarity:
Proc#1: -------------------------------------------------- #include
#include #include #include #include #include <iostream> #include "../shmem/ShmNode.hpp"
typedef std::pair< const int, ShmNode*> MyPair;
typedef boost::shmem::allocator < MyPair,
boost::shmem::named_shared_object::segment_manager> MyAlloc;
typedef boost::shmem::map< const int, ShmNode*, std::less<const int>, MyAlloc> MyMap;
int main() { boost::shmem::named_shared_object segment;
segment.create("/myshmem", 20000);
MyAlloc nodesAlloc(segment.get_segment_manager()); std::less<const int> comparator;
MyMap *table = segment.construct<MyMap>("table")(comparator, nodesAlloc);
MyPair myPair1(1, new ShmNode(1,2)); MyPair myPair2(2, new ShmNode(3,4)); MyPair myPair3(3, new ShmNode(5,6));
table->insert(myPair3); table->insert(myPair1); table->insert(myPair2);
return 0; } --------------------------------------------------
Proc#2 -------------------------------------------------- /* same includes */
/* same typedefs */
int main() { boost::shmem::named_shared_object segment; segment.open("/myshmem");
MyMap *table = segment.find<MyMap>("table").first;
std::cout << "table size: " << table->size() << std::endl;
MyMap::iterator iter; for (iter = table->begin(); ; iter++) { if (iter == table->end()) break; std::cout << iter->second->getA() << " " << iter->second->getB() << std::endl; } return 0; } --------------------------------------------------
The problem once again: in proc#2, iter->second->getA() and iter->second->getB() return 0. If I put the same loop into proc#1, the correct values are returned. As a further hint, the size of the map object in proc#2 is returned correctly (=3).
What am I doing wrong?
Regards, Szilard _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users