[PATCH] D64380: Add 'require_designated_init' and 'required' attribute to clang

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

C++20 designated initializers don't permit mixing designated fields with non-designated ones, so some of the examples here are invalid. However, I think we should be looking for an attribute design that works well in both C and C++, and with the various Clang extensions that permit the full generality of C designated initializers in other language modes. I also think this patch is combining multiple features that would be useful to expose separately. To that end, I think something like this might make sense:

- An attribute that can be applied to either a field or to a struct that requires a designator to be used on any initializer for that field (and for a struct, is equivalent to specifying the attribute on all fields)
- An attribute that can be applied to either a field or to a struct that requires an explicit initializer to be used for that field, for both aggregate initialization and constructor mem-initializer lists (and for a struct, is equivalent to specifying the attribute on all fields with no default member initializers)

Maybe `requires_designator` and `requires_init` or similar?

And I think these attributes should be made available in both C++11 attribute syntax and GNU attribute syntax. Inventing a C++-only extension to improve support for designated initializers doesn't seem like the right choice to me.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D64380/new/

https://reviews.llvm.org/D64380