Re: [PATCH v10 0/8] MR1628: ntdll: Implement Low Fragmentation Heap.

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/ntdll/heap.c:
> -
>    /* if GROUP_FLAG_FREE isn't set, thread is responsible for putting it back into group list. */
> -
>    if ((group = InterlockedExchangePointer( (void *)bin_get_affinity_group( bin, affinity ), group )))
> -
>        RtlInterlockedPushEntrySList( &bin->groups, (SLIST_ENTRY *)&group->entry );
> - }
> -
> - return block;
>
> +}
> -
>
> +static NTSTATUS heap_allocate_block_lfh( struct heap *heap, ULONG flags, SIZE_T block_size,
> -
>                                     SIZE_T size, void **ret )
>
> +{
> - struct bin *bin, *last = heap->bins + BLOCK_SIZE_BIN_COUNT - 1;
> - struct block *block;
> -
> - bin = heap->bins + BLOCK_SIZE_BIN( block_size );
> - if (!heap->bins || bin == last) return STATUS_UNSUCCESSFUL;

Can we avoid arithmetic on NULL pointer? It is undefined behavior, since it does not point to a valid object.[^note]

```suggestion:-4+0
    struct bin *bin;
    struct block *block;

if (!heap->bins) return STATUS_UNSUCCESSFUL;

bin = heap->bins + BLOCK_SIZE_BIN( block_size );
    if (bin == heap->bins + BLOCK_SIZE_BIN_COUNT - 1) return STATUS_UNSUCCESSFUL;
```

[^note]: https://stackoverflow.com/a/22104122