The problem is that your shared data (the single OverSharedData
object) contains pointers to non-shared data. You need to allocate all the data that you want shared in the shared memory segment, rather than with malloc. Something like:
static void *shared_available;
static size_t shared_left;
void init_shared(size_t size) {
key_t key = ftok("garbage.txt", 71);
int eyedee = shmget(key, size,
IPC_CREAT | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
if (eyedee == -1) {
perror("shmget");
exit(1); }
shared_available = shmat(eyedee, 0, 0);
if (shared_available == (void *) -1) {
perror("shmat");
exit(1); }
shared_left = size;
}
void *alloc_shared(size_t size) {
void *rv = shared_available;
if (size > shared_left) {
fprintf(stderr, "Ran out of shared memory!\n");
exit(1); }
shared_available = (char *)rv + size;
shared_left -= size;
return rv;
}
OverSharedData *initialize() {
init_shared(sizeof(struct OverSharedData) +
sizeof(struct SharedData *) * consumerthreads +
sizeof(struct SharedData) * consumerthreads)
OverSharedData *bill = alloc_shared(sizeof(OverSharedData));
bill->rep = alloc_shared(sizeof(struct SharedData*)*consumerthreads);
for (int on=0; on<consumerthreads; on++) {
bill->rep[on] = alloc_shared(sizeof(struct SharedData));
init(&bill->rep[on], on); }
}
The above will still have problems if the init
routine tries to store pointers to non-shared memory into the SharedData
struct (you don't show the definition of either, so we can't say).
If you want to be able to more flexibly allocate and manage shared memory across processes, you really need to use a general purpose shared memory allocator/manager, such as this