src/http/ngx_http_file_cache.c:1893: error: Integer Overflow L2
  ([0, +oo] - [0, 15]):unsigned64 by call to `ngx_slab_free_locked`.

src/http/ngx_http_file_cache.c:1893:9: Call
1891.         ngx_queue_remove(q);
1892.         ngx_rbtree_delete(&cache->sh->rbtree, &fcn->node);
1893.         ngx_slab_free_locked(cache->shpool, fcn);
              ^
1894.         cache->sh->count--;
1895.     }

src/core/ngx_slab.c:441:1: <LHS trace>
439. 
440. 
441. void
     ^
442. ngx_slab_free_locked(ngx_slab_pool_t *pool, void *p)
443. {

src/core/ngx_slab.c:441:1: Global `ngx_pagesize_shift`
  439. 
  440. 
  441. void
       ^
  442. ngx_slab_free_locked(ngx_slab_pool_t *pool, void *p)
  443. {

src/core/ngx_slab.c:441:1: <RHS trace>
439. 
440. 
441. void
     ^
442. ngx_slab_free_locked(ngx_slab_pool_t *pool, void *p)
443. {

src/core/ngx_slab.c:441:1: Parameter `pool->pages->slab`
  439. 
  440. 
  441. void
       ^
  442. ngx_slab_free_locked(ngx_slab_pool_t *pool, void *p)
  443. {

src/core/ngx_slab.c:458:5: Assignment
  456.     n = ((u_char *) p - pool->start) >> ngx_pagesize_shift;
  457.     page = &pool->pages[n];
  458.     slab = page->slab;
           ^
  459.     type = page->prev & NGX_SLAB_PAGE_MASK;
  460. 

src/core/ngx_slab.c:465:9: Assignment
  463.     case NGX_SLAB_SMALL:
  464. 
  465.         shift = slab & NGX_SLAB_SHIFT_MASK;
               ^
  466.         size = 1 << shift;
  467. 

src/core/ngx_slab.c:494:13: Binary operation: ([0, +oo] - [0, 15]):unsigned64 by call to `ngx_slab_free_locked` 
  492.             bitmap[n] &= ~m;
  493. 
  494.             n = (1 << (ngx_pagesize_shift - shift)) / 8 / (1 << shift);
                   ^
  495. 
  496.             if (n == 0) {
