Function ensure_pretrained_map

src/semantic/semantic.c:399–431

Thread-safe lazy init of the pretrained token lookup map. * Uses double-checked locking: fast path reads an atomic flag. */

/* Thread-safe lazy init of the pretrained token lookup map.
 * Uses double-checked locking: fast path reads an atomic flag. */
static void ensure_pretrained_map(void) {
    if (atomic_load_explicit(&g_pretrained_ready, memory_order_acquire)) {
        return;
    }
    /* First-time init of the mutex itself (also needs to be thread-safe) */
    int expected = MTX_STATE_UNINIT;
    if (atomic_compare_exchange_strong_explicit(&g_pretrained_mtx_init, &expected,
                                                MTX_STATE_INITIALIZING, memory_order_acq_rel,
                                                memory_order_acquire)) {
        cbm_mutex_init(&g_pretrained_mtx);
        atomic_store_explicit(&g_pretrained_mtx_init, MTX_STATE_READY, memory_order_release);
    } else {
        /* Spin until another thread finishes initializing the mutex */
        while (atomic_load_explicit(&g_pretrained_mtx_init, memory_order_acquire) !=
               MTX_STATE_READY) {
            /* brief spin */
        }
    }
    cbm_mutex_lock(&g_pretrained_mtx);
    if (!atomic_load_explicit(&g_pretrained_ready, memory_order_acquire)) {
        g_pretrained_map = cbm_ht_create(PRETRAINED_TOKEN_COUNT);
        char idx_buf[CBM_SZ_16];
        for (int i = 0; i < PRETRAINED_TOKEN_COUNT; i++) {
            const char *tok = PRETRAINED_TOKENS[i];
            if (tok && tok[0]) {
                snprintf(idx_buf, sizeof(idx_buf), "%d", i);
                cbm_ht_set(g_pretrained_map, strdup(tok), strdup(idx_buf));
            }
        }
        atomic_store_explicit(&g_pretrained_ready, MAP_READY, memory_order_release);
    }
    cbm_mutex_unlock(&g_pretrained_mtx);
}

void cbm_sem_ensure_ready(void) {
    ensure_pretrained_map();