[PATCH] D96838: Add GNU attribute 'retain'

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added inline comments.


================
Comment at: clang/include/clang/Basic/Attr.td:2655
+
+def Retain : InheritableAttr {
+  let Spellings = [GCC<"retain">];
----------------
aaron.ballman wrote:
> MaskRay wrote:
> > aaron.ballman wrote:
> > > Should this be a target-specific attribute as it only has effects on ELF targets?
> > As I understand it, GCC `retain` is not warned on unsupported targets.
> > 
> > Regardless of GCC's choice, I think not having a `warning: unknown attribute 'retain' ignored [-Wunknown-attributes]` diagnostic makes sense. `retain` will be usually used together with `used`. In Clang, `used` already has "retain" semantics on macOS and Windows (I don't know what they do on GCC; GCC folks want orthogonality for ELF and I agree). If `retain` is silently ignored on macOS and Windows, then users don't need to condition compile for different targets.
> The other side of that is a user who writes only `retain` and expects it to do something when it's actually being silently ignored. While they may usually use it in conjunction with `used`, I'm more worried about the situation where the user is possibly confused.
`retain` without `used` can be used on some external linkage definitions, as well as internal linkage definitions which are referenced by live sections. I agree there could be some confusion, but hope with mccall's suggestion (thanks) the documentation is clear.


Repository:
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  https://reviews.llvm.org/D96838/new/

https://reviews.llvm.org/D96838