[PATCH 5/5] ntoskrnl.exe: Make user shared data pointers volatile (GCC 11).

[Zebediah Figura]

On 9/27/21 3:58 AM, Rémi Bernon wrote:
> So that GCC 11 stops warning about reading from a 0-size memory region.
> 
> Signed-off-by: Rémi Bernon <rbernon at codeweavers.com>
> ---
>   dlls/ntoskrnl.exe/instr.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/dlls/ntoskrnl.exe/instr.c b/dlls/ntoskrnl.exe/instr.c
> index f197570db0c..fbcd376dbc1 100644
> --- a/dlls/ntoskrnl.exe/instr.c
> +++ b/dlls/ntoskrnl.exe/instr.c
> @@ -498,8 +498,8 @@ WINE_DEFAULT_DEBUG_CHANNEL(int);
>   #define SIB_BASE( sib, rex )    (((sib) & 7) | (((rex) & REX_B) ? 8 : 0))
>   
>   /* keep in sync with dlls/ntdll/thread.c:thread_init */
> -static const BYTE *wine_user_shared_data = (BYTE *)0x7ffe0000;
> -static const BYTE *user_shared_data      = (BYTE *)0xfffff78000000000;
> +static const BYTE *volatile wine_user_shared_data = (BYTE *)0x7ffe0000;
> +static const BYTE *volatile user_shared_data      = (BYTE *)0xfffff78000000000;
>   
>   static inline DWORD64 *get_int_reg( CONTEXT *context, int index )
>   {
> 

This looks wrong. It should presumably be "const volatile BYTE *" 
(actually: "const volatile BYTE *const"), but I'm guessing that doesn't 
actually fix the warning. Granted, there's an open GCC bug for this [1], 
and marking the variable volatile is suggested as a workaround...

Perhaps at least we should mark that we're working around a GCC bug in 
the code, since otherwise it looks like "volatile" is in the wrong place.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578