[Tarantool-patches] [PATCH 05/10] sql: make BtCursor's memory aligned

[Cyrill Gorcunov]

On Thu, May 21, 2020 at 10:37:28PM +0200, Vladislav Shpilevoy wrote:
> Vdbe at runtime allocates VdbeCursor structure using
> allocateCursor() function. Inside there is a pointer at BtCursor
> structure. To make the allocation faster and improve cache
> locality, both cursors are allocated in one memory block + some
> extra memory for uint32_t array, where BtCursor followed
> VdbeCursor and the array without any padding:
> 
>    VdbeCursor + uint32_t * N + BtCursor
> 
> The problem is that BtCursor needs 8 byte alignment. When it
> followed VdbeCursor (aligned by 8) + some uint32_t values, its
> actual alignment could become 4 bytes. That led to a crash when
> alignment sanitizer is enabled in clang.
> 
> The patch makes BtCursor offset aligned by 8 bytes.
> 
> Part of #4609
Reviewed-by: Cyrill Gorcunov <gorcunov at gmail.com>