[PATCH 0/1] MR2723: evr: Fix incorrect integral computation.

[eric pouech (＠epo)]

Note: typeof (int * unsigned) is unsigned.
So:
- on 64bit CPUs, where sizeof(int) = 4 < sizeof(void*) = 8,
- when the result of the multiplication is supposed to be negative
- there's no progation of the negative sign from 32bit to 64 bit integers

Fixes a crash in Age of Empire II.

Signed-off-by: Eric Pouech <epouech(a)codeweavers.com>

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/2723

[PATCH 1/1] evr: Fix incorrect integral computation.

[Eric Pouech]

From: Eric Pouech <epouech(a)codeweavers.com>

Note: typeof (int * unsigned) is unsigned.
So:
- on 64bit CPUs, where sizeof(int) = 4 < sizeof(void*) = 8,
- when the result of the multiplication is supposed to be negative
- there's no progation of the negative sign from 32bit to 64 bit integers

Fixes a crash in Age of Empire II.

Signed-off-by: Eric Pouech <epouech(a)codeweavers.com>
---
 dlls/evr/evr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dlls/evr/evr.c b/dlls/evr/evr.c
index 26a2a3a1eb5..611f6762844 100644
--- a/dlls/evr/evr.c
+++ b/dlls/evr/evr.c
@@ -382,7 +382,7 @@ static HRESULT evr_copy_sample_buffer(struct evr *filter, IMediaSample *input_sa
         {
             if (SUCCEEDED(hr = IDirect3DSurface9_LockRect(surface, &locked_rect, NULL, D3DLOCK_DISCARD)))
             {
-                if (src_stride < 0) src -= src_stride * (lines - 1);
+                if (src_stride < 0) src -= src_stride * (INT32)(lines - 1);
                 MFCopyImage(locked_rect.pBits, locked_rect.Pitch, src, src_stride, width * 4, lines);
                 IDirect3DSurface9_UnlockRect(surface);
             }
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/2723

[Nikolay Sivov (＠nsivov)]

Will it work if you made "lines" signed?

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/2723#note_31771

[eric pouech (＠epo)]

yes, any form that lets the result of the multiplication to be signed integer

so any of these will do
- make lines a signed int
- or cast (lines - 1) to a signed int
- or cast the result of the (unsigned) multiplication to a signed int

one could event prefer adding a positive integer to subtracting a negative one:
```
if (src_stride < 0) src += (-src_stride) * (lines - 1);
```
which I find more readable to show to intent to walk the image starting from last line in memory order

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/2723#note_31773

[Alexandre Julliard (＠julliard)]

> one could event prefer adding a positive integer to subtracting a negative one:
>
> ```
> if (src_stride < 0) src += (-src_stride) * (lines - 1);
> ```
>
> which I find more readable to show to intent to walk the image starting from last line in memory order

Yes, that's definitely better.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/2723#note_31780