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[0010] Clarify behavior of vk::aliased_pointer on vk::BufferPointer #95

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merged 4 commits into from
Nov 8, 2023
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[0010] Clarify behavior of vk::aliased_pointer on vk::BufferPointer #95

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a606931
[0010] Clarify behavior of vk::aliased_pointer
greg-lunarg Sep 8, 2023
ef17c4a
[0010] Add aliasing casting rules
greg-lunarg Oct 13, 2023
0177706
[0010] Add alias casting example
greg-lunarg Oct 13, 2023
ec520f9
[0010] Refer to aliasing casting example.
greg-lunarg Oct 13, 2023
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2 changes: 1 addition & 1 deletion proposals/0010-vk-buffer-ref.md
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Expand Up @@ -184,7 +184,7 @@ Applying HLSL semantic annotations to objects of type vk::BufferPointer is disal

By default, buffer pointers are assumed to be restrict pointers as defined by the C99 standard.

An attribute vk::aliased_pointer can be attached to a variable, function parameter or a block member of buffer pointer type. It is assumed that the pointee of an object with this attribute can overlap with the pointee of any other object with this attribute.
An attribute vk::aliased_pointer can be attached to a variable, function parameter or a block member of BufferPointer type. It ie assumed that the pointee of a BufferPointer with this attribute can overlap with the pointee of any other BufferPointer with this attribute. This also means that the pointee of a BufferPointer with this attribute does not overlap with the pointee of a default (restrict) BufferPointer.
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Looks like you introduced a typo "It ie assumed ...".

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The meaning of the restrict attribute only applies to a scope.

For example the following is allowed in C:

int foo(restrict int* p) {
  return *p;
}

int func(int * p) {
  return foo(p); // implicit cast from "aliased" to "restrict".
}

The extra sentence you added is not true. An aliased pointer and restrict pointer can point to overlapping storage as long as the aliased pointer is not used during the lifetime of the restrict pointer.

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I agree this PR does not necessarily address #87. I will attempt to redress that.

I am not sure I agree that my "extra" statement above is false, although perhaps underspecified. My statement above assumes that the two pointers in question have overlapping scopes. If they don't have overlapping scopes, than their overlapping memory is moot, it seems to me. But I will add that the pointers have overlapping scopes to clarify.


### Buffer Pointers and Address Space

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