Khronos Public Bugzilla
Bug 876 - shared buffer layout and querying variables
shared buffer layout and querying variables
Status: ASSIGNED
Product: OpenGL
Classification: Unclassified
Component: API Specification
4.3
All All
: P3 normal
: ---
Assigned To: johnk
:
Depends on:
Blocks:
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Reported: 2013-05-24 04:45 PDT by Alfonse
Modified: 2013-07-15 12:01 PDT (History)
1 user (show)

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Description Alfonse 2013-05-24 04:45:38 PDT
The `shared` layout qualifier means that the layout of a particular set of variables in a block will be identical, so long as all blocks share the same definition. However, this does *not* mean that all of the members of a `shared` block are considered "active". Which means that you aren't guaranteed to be able to query the full layout for such a block from any program you compile that uses the shared block.

This is not a phantasmal issue; it is real and is really affecting code. NVIDIA's current drivers apparently will not consider shared uniforms active unless they're used. And the specification seems to allow this. See here for details: http://www.opengl.org/discussion_boards/showthread.php/181747-Nvidia-319-320-drivers-and-shared-layout-UBOs

The specification should *not* permit this.
Comment 1 johnk 2013-07-15 12:01:48 PDT
I believe this related to something we have been recently working on internally, and will update here once that's confirmed and with the result.