[Mesa-dev] [PATCH] mesa: fix MSVC bitshift overflow warnings
Mathias Fröhlich
Mathias.Froehlich at gmx.net
Fri Mar 30 15:19:24 UTC 2018
On Friday, 30 March 2018 17:09:40 CEST Brian Paul wrote:
> In the BITFIELD_MASK() macro, if b==32 the expression evaluates to
> ~0u, but the compiler still sees the expression (1 << 32) in the
> unused part and issues a warning about integer bitshift overflow.
>
> Fix that by using (b) % 32 to ensure the max shift is 31 bits.
>
> This issue has been present for a while, but shows up much more
> often because of the recent VBO changes.
> ---
> src/mesa/main/mtypes.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 801bd17..b7a7b34 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -59,7 +59,7 @@ extern "C" {
> #define BITFIELD_BIT(b) ((GLbitfield)1 << (b))
> /** Set all bits up to excluding bit b */
> #define BITFIELD_MASK(b) \
> - ((b) == 32 ? (~(GLbitfield)0) : BITFIELD_BIT(b) - 1)
> + ((b) == 32 ? (~(GLbitfield)0) : BITFIELD_BIT((b) % 32) - 1)
> /** Set count bits starting from bit b */
> #define BITFIELD_RANGE(b, count) \
> (BITFIELD_MASK((b) + (count)) & ~BITFIELD_MASK(b))
>
Definitely:
Reviewed-by: Mathias Fröhlich <mathias.froehlich at web.de>
best
Mathias
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