C struct being passed thru a linux msg queue failing intermittently - c

Question

I have a client process that builds an IPC message struct queue_msg that is being sent to a server via the linux IPC msg queue. 68 bytes in size. struct is defined as:
struct FOO_TYPE {
long mtype;
struct {
int sev;
char msg[32];
char bt[32];
} foomsg;
};
the client declares a pointer to the a struct of FOO_TYPE locally in the function and mallocs space for it. the code then loads the sev, msg and bt fields.
static struct FOO_TYPE *FooEntry = NULL;
...code clipped
if (FooEntry == NULL)
FooEntry = malloc(sizeof(struct FOO_TYPE));
memset(FooEntry, 0, sizeof(struct FOO_TYPE));
...code clipped
MsgSize = sizeof(FooEntry) - sizeof(long);
FooEntry->mtype = CHANGESTATUS;
FooEntry->foomsg.sev = serr->serr_data->sev;
strcpy(FooEntry->syserrmsg.emsg, elog);
strcpy(FooEntry->syserrmsg.bt, btlog);
... code clipped
result = msg_snd(FooExchange, FooEntry, MsgSize, IPC_WAIT);
the server receiving the IPC msg is getting 68 bytes (ie: sizeof FOO_TYPE), however intermittently, the fields inside are either missing or garbage.
do I have to malloc space for the fields in the struct inside the structure as well??

Answer 1

This is at least one bug:
MsgSize = sizeof(FooEntry) - sizeof(long);
FooEntry is a pointer defined here:
static struct FOO_TYPE *FooEntry = NULL;
so sizeof(FooEntry) gives you the size of a pointer - not the size of a struct.
You probably want
MsgSize = sizeof(*FooEntry) - sizeof(long);
or perhaps just
MsgSize = sizeof(FooEntry->foomsg);