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ASSS Questions - Where should pointers used in arenadata be initialized?

Bak - Thu Jun 17, 2004 3:16 pm
Post subject: Where should pointers used in arenadata be initialized?

I'm looking at balls.c and how it handles per arena data allocation:

abdkey = aman->AllocateArenaData(sizeof(ArenaBallData));

so it gets a key for the data... now I'd assume any pointers in the data (like BallData *balls) would now contain a random value until i amalloc or malloc something for it. So my question is, where does this value get initialized?

The obvious answer is when the arena is created, so I looked in the AABall function:

void AABall(Arena *arena, int action)
{
/* create the mutex if necessary */
if (action == AA_CREATE)
{
pthread_mutexattr_t attr;

pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init((pthread_mutex_t*)P_ARENA_DATA(arena, mtxkey), &attr);
pthread_mutexattr_destroy(&attr);
}

LOCK_STATUS(arena);
if (action == AA_CREATE || action == AA_DESTROY)
{
ArenaBallData *abd = P_ARENA_DATA(arena, abdkey);

/* clean up old ball data */
if (abd->balls)
{
afree(abd->balls);
abd->balls = NULL;
}
abd->ballcount = 0;
}
if (action == AA_CREATE)
{
/* only if we're creating, load the data */
load_ball_settings(arena, 1);
}
....

it looks like the first thing it does if action == AA_CREATE is create some thread stuff... then it does if (action == AA_CREATE || action == AA_DESTROY)
and if (abd->balls)

then it'll free the memory pointed to by abd->balls. But if abd->balls is a random value(just been allocated) wouldn't it be trying to free a random memory location? It doesn't. I put a check in and when the arena is created abd->balls is zero so it skips that if statement. But where does abd become zero??? when you do allocatearenadata does it initialize all the data to zero?

Also: when should I do LOCK_STATUS(arena); and UNLOCK_STATUS(arena); ??? is that whenever I get or modify arena data? what about when I get player data? LOCK_PLAYER?

Thanks!!!

Smong - Fri Jun 18, 2004 2:26 pm
Post subject:

The per arena/player data is always zero'd for you. (If you look in util.c amalloc() sets the mem to 0).

The LOCK_STATUS() is a macro specific only to the source file it is defined in. It is most likely used so two callbacks don't try and write to the same data at the same time (or maybe one callback is reading data).