Re: [PATCH 0/1] MR3936: gdiplus/tests: add tests of InterpolationMode Bilinear for GdipDrawImagePointsRect

[Jeffrey Smith (＠whydoubt)]

Jeffrey Smith (@whydoubt) commented about dlls/gdiplus/tests/image.c:
> }
>  }
>
> +INT compare_with_precision(const void *ptr1, const void *ptr2, size_t num, INT precision)
> +{
> +  if (ptr1 == NULL || ptr2 == NULL)
> +    return ptr1 < ptr2 ? -1 : 1;
> +
> +  for (size_t i = 0; i < num; i++)
> +  {
> +    unsigned char byte1 = *((unsigned char *)ptr1 + i);
> +    unsigned char byte2 = *((unsigned char *)ptr2 + i);
> +
> +    if ((byte1 < byte2 - precision) || (byte1 > byte2 + precision))

I believe the operations here could over/under-flow.  Seems like that may cause problems.

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https://gitlab.winehq.org/wine/wine/-/merge_requests/3936#note_46694