Spec doesn't specify the behavior of vkCmdTraceRayKHR with zero addressed shader binding table.

[kevyuu]

These VUIDs below implies that zero addressed SBT for miss and hit shader group is valid and have a special behavior, yet the behavior is not specified in the spec.

(https://docs.vulkan.org/spec/latest/chapters/raytracing.html#VUID-vkCmdTraceRaysKHR-flags-03696)
(https://docs.vulkan.org/spec/latest/chapters/raytracing.html#VUID-vkCmdTraceRaysKHR-flags-03697)
(https://docs.vulkan.org/spec/latest/chapters/raytracing.html#VUID-vkCmdTraceRaysKHR-flags-03511)

Furthermore from experimentation, validation layer does not trigger a complain that these zero addressed SBT have to be created with VK_BUFFER_USAGE_SHADER_BINDING_TABLE_BIT to follow this. This and other exceptions for zero addressed SBT affirm my believe that zero address have a special semantic that is not documented.