pthread_mutex_init result in Segmentation Fault - c

Question

I'm a college student learning how to deal with threads and databases.
Overall, I'm trying to make a function that will take a list of locks, see if the current lock the program is handling is in the list, and mutex lock that lock.
Currently, I am having issues initializing the *locks, but every time I do so, I get a segmentation error (core dump).
I already try using the different ways of initializing the mutex lock:
&locks->lock = PTHREAD_MUTEX_INITIALIZER;
as well as using : pthread_mutex_init(&locks->lock, NULL);
on the .h file, it contains
typedef struct {
char *table;
pthrad_mutex_t lock;} TableLock;
main file:
static pthread_mutex_t lock_on_locks;
static int active_tables = 0;
static TableLock *locks = NULL;
// Table locking functions
void sudba_lock(char *table) {
sleep(2);
if (locks == NULL) {
my_realloc(locks, sizeof(TableLock));
}
pthread_mutex_lock(&lock_on_locks);
char table_name[strlen(table) + 1];
table_name[strlen(table)] = '\0';
sprintf(table_name, "%s", table);
if (active_tables == 0) {
pthread_mutex_init(&locks->lock, NULL);
pthread_mutex_lock(&locks->lock);
locks[active_tables].table = table_name;
active_tables++;
}
the my_realloc function is this:
void *my_realloc(void *ptr, size_t size) {
void *result = malloc(size);
if(!result) abort();
return result
}
Any help is appreciated

Answer 1

Your crash has nothing to do with pthread_mutex_lock; it's just that you're passing a null pointer to it because you didn't save the result of realloc. Where you have:
my_realloc(locks, sizeof(TableLock));
it should be:
locks = my_realloc(locks, sizeof(TableLock));
But I'm not clear why you're allocating it anyway since this looks like a single-instance lock. Normally locks either have static storage duration or exist inside some structure you're allocating (whose contents they'll protect). Allocating an individual lock by itself is a code smell.
There are a lot of other things that look wrong with your code too, independent of the crash.