I have tried to use Boost and had a segv after 3000 allocations of objects of size 24, now i started to use sys/ipc.h and sys/shm.h , i allocate 25 mio bytes (if i understand this properly)
it seems also to work properly on my linux box ipcs -m will show the allocated segment
0x000081bc 917516 testUser 644 25000000 0
sysctl -p will print
kernel.shmmax = 25500000
For some reason it works until the program reaches "43406 x 24 bytes" that's the place it will segv. I would be glad to get some hints where my problem lies. Please also note if this is the wrong way to allocate and use the shared memory with objects.
#define MAXMYMEM 25000000
int sharedMemId;
x *p_sharedMemory;
x *p_other;
sharedMemId = shmget(2232, MAXMYMEM, IPC_CREAT | 0644);
if(sharedMemId >= 0){
p_sharedMemory = (x*) shmat( sharedMemId, 0 , 0);
if(p_sharedMemory != ( x *)-1) {
cout << sizeof(x) << endl;
for(unsigned int i = 0 ; i < 1000000;i++ ){
(p_sharedMemory + (sizeof(x) * i))->setTest(i);
}
(p_sharedMemory + (sizeof(x) * i))->setTest(i);
Why are you using sizeof(x) here? Adding one to a pointer that points to an x will point at the next x, not the next byte. I suspect this is your problem.
change (p_sharedMemory + (sizeof(x) * i))->setTest(i); to
++p_sharedMemory;
p_sharedMemory->setTest(i);