[Interprocess] Using shared Memory with different compilers (msvc, mingw)

hi, My library uses boost::interprocess' Shared Memory and has to be delivered with msvc(7.1) and mingw compiled versions. Every instance of the that library opens a connection to the Shared Memory "sharedMemoryMapTest" and communicates via instances of the class "SyncObject". In my test program ProcessA opens the shared memory, instanciates a SynObject with the identifyer String "id1". ProcessB connects to the same SyncObject and synchronizes with ProcessA. If ProcessA and ProcessB are both compiled with the same compiler it works fine. If one process is compiled with mscv and the other is compiled with mingw it fails. (mscv = ProcessA, ProcessB = mingw -> I read my Windows environment variables instead of "id1") Did I make a mistake in my implementation, or is it simply not possible to access the same Shmem with different compiled versions? Thanks in advance Martin (compilable) code: #include <iostream> #include <boost/interprocess/managed_shared_memory.hpp> #include <boost/interprocess/allocators/allocator.hpp> #include <boost/interprocess/containers/string.hpp> #include <boost/interprocess/containers/list.hpp> typedef unsigned long U32; using namespace boost::interprocess; class SyncObject { public: SyncObject(std::string aId) : id(aId), locAddrSp0Range(0), locAddrSp0Remap(0), locAddrSp1Range(0), locAddrSp1Remap(0), usbInterfaceOwner(0), useCounter(0) {} ; ~SyncObject() { std::cout << "SyncObject Destructor\n" << std::flush; }; void print() { std::cout << " id = " << id << " locAddrSp0Range = " << locAddrSp0Range << " locAddrSp0Remap = " << locAddrSp0Remap << " locAddrSp1Range = " << locAddrSp1Range << " locAddrSp1Remap = " << locAddrSp1Remap << " usbInterfaceOwner = " << usbInterfaceOwner << " useCounter = " << useCounter << "\n" << std::flush; }; std::string id; interprocess_mutex mtxReadWrite; interprocess_mutex mtxFunction; U32 locAddrSp0Range; U32 locAddrSp0Remap; U32 locAddrSp1Range; U32 locAddrSp1Remap; U32 usbInterfaceOwner; U32 useCounter; }; const char* MANAGED_SHARED_MEMORY_NAME = "sharedMemoryMapTest58"; const char* SYNC_OBJ_LIST_NAME = "sharedMemorySyncList"; typedef offset_ptr<SyncObject> SyncObjOffsetPtr; typedef allocator<SyncObjOffsetPtr, managed_shared_memory::segment_manager> SyncObjOffsetPtrAllocator; typedef list<SyncObjOffsetPtr, SyncObjOffsetPtrAllocator> SyncObjectList; class SharedMemory { public: SharedMemory(); ~SharedMemory(); void printList(); SyncObject* getSyncObject(std::string id); void removeSyncObject(std::string id); private: managed_shared_memory segment; }; SharedMemory::SharedMemory() { segment = managed_shared_memory(open_or_create, MANAGED_SHARED_MEMORY_NAME, 65536); } SharedMemory::~SharedMemory() { std::cout << "SharedMemory Destuctor\n" << std::flush; SyncObjectList* pList = segment.find<SyncObjectList>(SYNC_OBJ_LIST_NAME).first; if (pList) { if (pList->size() < 1) { segment.destroy_ptr(pList); std::cout << "pList destroyed! \n" << std::flush; } } // unlink shared mem object // shared_memory_object::remove(MANAGED_SHARED_MEMORY_NAME); if( shared_memory_object::remove(MANAGED_SHARED_MEMORY_NAME)) std::cout << MANAGED_SHARED_MEMORY_NAME << " successfully removed from the system!\n" << std::flush; else std::cout << MANAGED_SHARED_MEMORY_NAME << " could not be removed from the system!\n" << std::flush; } void SharedMemory::printList() { SyncObjectList* pList = segment.find<SyncObjectList>(SYNC_OBJ_LIST_NAME).first; if (!pList) { std::cout << "List does not exist!\n" << std::flush; return; } std::cout << "list contains: "; for(SyncObjectList::iterator iter = pList->begin(); iter != pList->end(); ++iter ) { std::cout << iter->get()->id << "\t"; } std::cout << "\n" << std::flush; } SyncObject* SharedMemory::getSyncObject(std::string id) { //Initialize shared memory STL-compatible allocator const SyncObjOffsetPtrAllocator syncObjOffsetPtrAllocatorInst (segment.get_segment_manager()); SyncObjectList* pList = segment.find_or_construct<SyncObjectList>(SYNC_OBJ_LIST_NAME)(syncObjOffsetPtrAllocatorInst); printList(); for(SyncObjectList::iterator iter = pList->begin(); iter != pList->end(); ++iter ) { if (iter->get()->id == id) { std::cout << id << " already exists in SHMem! returning pointer\n"; iter->get()->useCounter++; return iter->get(); } } std::cout << id << " is not in the list and will be created in SHMem!\n"; SyncObject* ptr = segment.construct<SyncObject>(id.c_str())(id); ptr->useCounter++; pList->push_back(offset_ptr<SyncObject>(ptr)); return ptr; } void SharedMemory::removeSyncObject(std::string id) { //Initialize shared memory STL-compatible allocator const SyncObjOffsetPtrAllocator syncObjOffsetPtrAllocatorInst (segment.get_segment_manager()); SyncObjectList* pList = segment.find_or_construct<SyncObjectList>(SYNC_OBJ_LIST_NAME)(syncObjOffsetPtrAllocatorInst); printList(); for(SyncObjectList::iterator iter = pList->begin(); iter != pList->end(); ++iter ) { if (iter->get()->id == id) { if (iter->get()->useCounter < 2) { std::cout << "removing " << id << " from list \n" << std::flush; SyncObject *ptr = iter->get(); segment.destroy_ptr(ptr); pList->erase(iter); } else { std::cout << "decrementing userCounter of id " << id << "\n" << std::flush; iter->get()->useCounter--; } break; } } } int main() { try { SharedMemory shm; SyncObject *pSync = shm.getSyncObject("id1"); pSync->mtxFunction.lock(); pSync->print(); pSync->locAddrSp0Range++; pSync->print(); pSync->mtxFunction.unlock(); shm.removeSyncObject("id1"); pSync = shm.getSyncObject("id1"); pSync->mtxFunction.lock(); pSync->print(); pSync->locAddrSp0Range++; pSync->print(); pSync->mtxFunction.unlock(); shm.removeSyncObject("id1"); } catch(boost::interprocess::interprocess_exception &ex) { std::ostringstream sout; sout.str(""); sout << ex.what(); std::cout << sout.str() << std::flush; } return 0; } -- Neu: GMX DSL bis 50.000 kBit/s und 200,- Euro Startguthaben! 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AMDG BaDBuTz wrote:
My library uses boost::interprocess' Shared Memory and has to be delivered with msvc(7.1) and mingw compiled versions.
Every instance of the that library opens a connection to the Shared Memory "sharedMemoryMapTest" and communicates via instances of the class "SyncObject".
In my test program ProcessA opens the shared memory, instanciates a SynObject with the identifyer String "id1". ProcessB connects to the same SyncObject and synchronizes with ProcessA. If ProcessA and ProcessB are both compiled with the same compiler it works fine. If one process is compiled with mscv and the other is compiled with mingw it fails. (mscv = ProcessA, ProcessB = mingw -> I read my Windows environment variables instead of "id1")
Did I make a mistake in my implementation, or is it simply not possible to access the same Shmem with different compiled versions?
You can't use std::string in shared memory. It probably works in this case because of SBO. Regardless, you can't safely use Interprocess with different compilers because the ABI can be different depending on the compiler. In Christ, Steven Watanabe

hi Steven, I'll change the std::string to boost::interprocess::basic_string::string or basic_string. What does SBO stand for? I searched the web but couldn't find anything. Can I use interprocess with different compilers, if I store the elements of the SyncObject(U32 values, mutexes, strings) directly in the Shmem without wrapping them into the SyncObject container? example: pMtxReadWrite = segment.construct<interprocess_mutex>(id.c_str() + "_mtx"); plocAddrSp0Range = segment.construct<U32>(id.c_str() + "_locAddrSp0Range"); then I use the pointers now as if they are in the SyncObject before. Best regards Martin Steven Watanabe schrieb:
AMDG
BaDBuTz wrote:
My library uses boost::interprocess' Shared Memory and has to be delivered with msvc(7.1) and mingw compiled versions.
Every instance of the that library opens a connection to the Shared Memory "sharedMemoryMapTest" and communicates via instances of the class "SyncObject".
In my test program ProcessA opens the shared memory, instanciates a SynObject with the identifyer String "id1". ProcessB connects to the same SyncObject and synchronizes with ProcessA. If ProcessA and ProcessB are both compiled with the same compiler it works fine. If one process is compiled with mscv and the other is compiled with mingw it fails. (mscv = ProcessA, ProcessB = mingw -> I read my Windows environment variables instead of "id1")
Did I make a mistake in my implementation, or is it simply not possible to access the same Shmem with different compiled versions?
You can't use std::string in shared memory. It probably works in this case because of SBO. Regardless, you can't safely use Interprocess with different compilers because the ABI can be different depending on the compiler.
In Christ, Steven Watanabe
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AMDG BaDBuTz wrote:
I'll change the std::string to boost::interprocess::basic_string::string or basic_string.
What does SBO stand for? I searched the web but couldn't find anything.
Small buffer optimization. In this case, it means that small strings will be stored directly in the string object instead of being allocated on the heap.
Can I use interprocess with different compilers, if I store the elements of the SyncObject(U32 values, mutexes, strings) directly in the Shmem without wrapping them into the SyncObject container?
example: pMtxReadWrite = segment.construct<interprocess_mutex>(id.c_str() + "_mtx"); plocAddrSp0Range = segment.construct<U32>(id.c_str() + "_locAddrSp0Range");
then I use the pointers now as if they are in the SyncObject before.
I don't think it matters. Unless the internal data structures used by Interprocess and all the types involved have exactly the same layout you can't use managed_shared_memory with different compilers. In Christ, Steven Watanabe
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