for(vector<const Program::UniformInfo *>::const_iterator i=block.uniforms.begin(); i!=block.uniforms.end(); ++i)
{
SlotMap::const_iterator j = uniform_slots.find((*i)->name);
+ /* TODO issue a warning (or even error?) either here or in update_block
+ if all uniforms for a buffer-backed block are not found */
if(j!=uniform_slots.end() && j->second<MASK_BITS)
mask |= 1<<j->second;
}