On 05/15/2017 02:27 AM, Nicolai Hähnle wrote:
> Hi all,
>
> This series aims to simplify how we handle unnamed struct types and fix some
> bugs on the way. Some of the patches should be uncontroversial, and all of
> them align with my understanding of the GLSL spec, but the spec isn't
> exactly explicit, so...
>
> At a high level, the series changes two things:
>
> 1) Unnamed structs can never match named structs during linking.
>
> 2) Unnamed structs are considered the same type if they have the same
> content. They will literally use the same glsl_type instance.
>
> The second point causes a deviation from the behavior of C/C++, in that the
> following code snippet now compiles (and does the reasonable thing):
>
> struct { float a; } s1;
> struct { float a; } s2;
>
> s2 = s1;
I'll have to do some archaeology, but I believe this is what we used to
do. I believe that we changed it because we were required to do so.
Does this fix some app, or is it just to simplify the code?
> The justification is basically that the GLSL spec says (when it comes to
> linking, in Section 4.2) that
>
> "Structures must have the same name, sequence of type names, and
> type definitions, and member names to be considered the same type."
>
> And since people generally seem to read that as mandating that globals of
> unnamed struct types should match if they're structurally the same, and the
> GLSL spec otherwise says nothing (as far as I can tell) about when struct
> types are equal, the cleanest thing is to just say that _in general_ (not
> just for linking) struct types are the same if and only if they have the
> same name and the same fields; where "same name" can mean that they both
> have no name.
>
> Please contemplate and review! :)
> Thanks,
> Nicolai
> --
> src/compiler/glsl/ast.h | 1 +
> src/compiler/glsl/ast_to_hir.cpp | 17 ++---
> src/compiler/glsl/glsl_parser_extras.cpp | 17 +++--
> src/compiler/glsl/link_varyings.cpp | 41 +++---------
> src/compiler/glsl/linker.cpp | 47 +++++---------
> src/compiler/glsl/lower_ubo_reference.cpp | 2 +-
> src/compiler/glsl_types.cpp | 69 +++++++++------------
> src/compiler/glsl_types.h | 11 ++--
> 8 files changed, 80 insertions(+), 125 deletions(-)
>
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