[PATCH 1/2] comctl32/listbox: Fix InitStorage heap extension

[Huw Davies]

On 18 Sep 2018, at 21:10, Gabriel Ivăncescu <gabrielopcode at gmail.com> wrote:
> 
> Signed-off-by: Gabriel Ivăncescu <gabrielopcode at gmail.com>
> ---
> 
> Only increase the item array if we actually have to. Previously, sending 1 to
> nb_items repeatedly would always increase the array by LB_ARRAY_GRANULARITY,
> even if there was plenty of space.
> 
> dlls/comctl32/listbox.c | 18 +++++++++++-------
> 1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/dlls/comctl32/listbox.c b/dlls/comctl32/listbox.c
> index 2137ef8..9cd89ff 100644
> --- a/dlls/comctl32/listbox.c
> +++ b/dlls/comctl32/listbox.c
> @@ -673,16 +673,20 @@ static LRESULT LISTBOX_InitStorage( LB_DESCR *descr, INT nb_items )
> {
>     LB_ITEMDATA *item;
> 
> -    nb_items += LB_ARRAY_GRANULARITY - 1;
> -    nb_items -= (nb_items % LB_ARRAY_GRANULARITY);
>     if (descr->items) {
> -        nb_items += HeapSize( GetProcessHeap(), 0, descr->items ) / sizeof(*item);
> -	item = HeapReAlloc( GetProcessHeap(), 0, descr->items,
> -                              nb_items * sizeof(LB_ITEMDATA));
> +        nb_items += descr->nb_items;
> +        if (nb_items > HeapSize(GetProcessHeap(), 0, descr->items) / sizeof(*item))
> +        {
> +            UINT n = nb_items + LB_ARRAY_GRANULARITY - 1;
> +            item = HeapReAlloc(GetProcessHeap(), 0, descr->items,
> +                               (n - n % LB_ARRAY_GRANULARITY) * sizeof(*item));

I dislike having the calculation split up like this.

Further, I think we can insist that LB_ARRAY_GRANULARITY is a power of two,
(perhaps add a comment to that effect above its #define) which should
simplify things a bit.

Huw.