On 11/01/2017 10:33 AM, Roland Scheidegger wrote:
Oh no msvc enums strike again... (A real pity c doesn't allow to explicitly make enums signed or unsigned.)
There's a proposal for that feature for a future std C version.
We use bitfields for compact representation, so if we need an extra bit that seems a bit counterintuitive (even if it dosen't increase the overall size here). Also, I believe the 16 bits for format were chosen for slightly more efficient code. Worse though, needing one bit more than everybody thinks is necessary looks error-prone to me (albeit in this case it seems very unlikely the enum gets more values).
I'll certainly be on the lookout for this issue in the future.
But I guess the alternative would be to just use unsigned:4 for the target. Not sure if that would be preferable, there's really no good solution, but in any case Reviewed-by: Roland Scheidegger <srol...@vmware.com>
Thanks. -Brian
Am 01.11.2017 um 15:45 schrieb Brian Paul:MSVC treats enums as being signed. The 4-bit target field isn't large enough to correctly store the value 8 (for PIPE_TEXTURE_CUBE_ARRAY). The bitfield value 0x8 was being interpreted as -8 so matching the target with PIPE_TEXTURE_CUBE_ARRAY in switch statements, etc. was failing. To keep the structure size the same, we reduce the format field from 16 bits to 15. There don't appear to be any other enum bitfields which need to be adjusted. This fixes a number of Piglit cube map array tests. --- src/gallium/include/pipe/p_state.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/src/gallium/include/pipe/p_state.h b/src/gallium/include/pipe/p_state.h index 10bf678..90dc561 100644 --- a/src/gallium/include/pipe/p_state.h +++ b/src/gallium/include/pipe/p_state.h @@ -34,6 +34,10 @@ * Basic notes: * 1. Want compact representations, so we use bitfields. * 2. Put bitfields before other (GLfloat) fields. + * 3. enum bitfields need to be at least one bit extra in size so the most + * significant bit is zero. MSVC treats enums as signed so if the high + * bit is set, the value will be interpreted as a negative number. + * That causes trouble in various places. */ @@ -436,8 +440,8 @@ struct pipe_surface struct pipe_sampler_view { struct pipe_reference reference; - enum pipe_format format:16; /**< typed PIPE_FORMAT_x */ - enum pipe_texture_target target:4; /**< PIPE_TEXTURE_x */ + enum pipe_format format:15; /**< typed PIPE_FORMAT_x */ + enum pipe_texture_target target:5; /**< PIPE_TEXTURE_x */ unsigned swizzle_r:3; /**< PIPE_SWIZZLE_x for red component */ unsigned swizzle_g:3; /**< PIPE_SWIZZLE_x for green component */ unsigned swizzle_b:3; /**< PIPE_SWIZZLE_x for blue component */
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