c++ - Memory issues with threads -


i'm working on multi-threaded server application. have struct try pass 2 threads:

struct params{   safequeue<int> *mq;   database *db; }; class server{   server(database *db){     dword sthread, ethread;     params *p;     p = new params;     p->db = db;     safequeue<int> *msgq = new safequeue<int>;     p->mq = msgq;     cout << "address of params: " << p << endl;     cout << "address of safequeue: " << msgq << endl;     cout << "starting server...\n";     createthread(null, 0, smtpreceiver, &p, 0, &sthread);      createthread(null, 0, mqueue, &p, 0, &ethread);   } } dword winapi mailqueue(lpvoid lpparam){   params *p = (params *) lpparam;   safequeue<int> *msgq = p->mq;   cout << "address of params: " << p << endl;   cout << "address of safequeue: " << msgq << endl;   cout << "queue thread started...\n"; }

now issue i'm having pointer safequeue in mailqueue thread has address of params struct... see output:

address of params: 0x23878 address of safequeue: 0x212c8 starting server... address of params: 0x28fe60 address of safequeue: 0x23878 queue thread started... 

createthread(null, 0, mqueue, &p, 0, &ethread);                               ^^

this should p

you pass params** mailqueue thread cast params* , dereference it, that's undefined behaviour. happens in practice p->mq address @ *p (because offsetof(params, mq) == 0) value of p in server constructor, you're seeing in cout output.

to fix it, should passing params* new thread, i.e. variable p not address.


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