Re: [RFC (fix for 5.0?)] block/io: do not do pointer arithmetic on void *

[Daniel P . Berrangé]

On Wed, Mar 18, 2020 at 05:22:53PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> 
> Hi all!
> 
> C standard doesn't allow pointer arithmetic on void *.
> Still, gcc allows it as an extension:
>  https://gcc.gnu.org/onlinedocs/gcc-4.8.0/gcc/Pointer-Arith.html
> 
> I can create a series of patches like this. Do we need it?

I don't think so, we only care about gcc & clang.

> Also, where is documented which compilers are supported by Qemu?

It is checked in configure - gcc 4.8 or clang 3.4 or xcode clang 5.1

> 
>  block/io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/io.c b/block/io.c
> index aba67f66b9..539178aed5 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1277,7 +1277,7 @@ static int coroutine_fn 
> bdrv_co_do_copy_on_readv(BdrvChild *child,
>       * modifying the image file.  This is critical for zero-copy guest I/O
>       * where anything might happen inside guest memory.
>       */
> -    void *bounce_buffer = NULL;
> +    char *bounce_buffer = NULL;
>  
>      BlockDriver *drv = bs->drv;
>      int64_t cluster_offset;
> -- 
> 2.21.0
> 
> 

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|