[PATCH] D30009: Add support for '#pragma clang attribute'

[Reid Kleckner via Phabricator via cfe-commits]

rnk added inline comments.


================
Comment at: docs/LanguageExtensions.rst:2349
+attribute is supported by the pragma by referring to the
+:doc:`individual documentation for that attribute <AttributeReference>`.
----------------
arphaman wrote:
> efriedma wrote:
> > arphaman wrote:
> > > arphaman wrote:
> > > > efriedma wrote:
> > > > > I'm wondering if we can tweak the approach so that we don't have to separately define how this works for each attribute; for example, `#pragma clang attribute_function_declaration push(...)` would apply to each function declaration, `#pragma clang attribute_global_variable_declaration push(...)` would apply to each global variable declaration, etc.
> > > > I agree with this idea, I think it would be useful to have the ability to specify the target declarations. I do think it would be better to use the 'clang attribute' umbrella pragma, and maybe add an extra argument to the 'push', e.g.:
> > > > 
> > > > ```
> > > > #pragma attribute push (annotate("functions-only"), applicable_to=function) // or maybe received_by=?
> > > > #pragma attribute push (annotate("struct+enum"), applicable_to=struct, applicable_to=enum)
> > > > ```
> > > I think that the further tweaks that control which declarations receive the attributes should be kept for a follow-up patch.
> > I'm not sure we can wait to address this, especially if we're turning this on for all attributes by default.  There's a compatibility hazard here: if the push doesn't specify what declarations it applies to, we can never change AttributeAppliesToDecl for any existing attribute.
> Are you saying that we should never allow a push without specifying which declarations should the attribute apply to? I think that would make this feature less useful, as some attributes have a well defined set of declarations that they apply to. Even if we will change the attribute's subjects in the future, I think it might be more likely that the users would've wanted to apply the attribute to the updated compiler-determined subject list.
I agree, users shouldn't have to repeat that attribute "target" applies to functions and attribute "warn_unused" applies to record types. Asking the user to figure it out just makes it harder to use.


Repository:
  rL LLVM

https://reviews.llvm.org/D30009