[PATCH] D31343: Add an attribute plugin example

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


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Comment at: clang/examples/Attribute/Attribute.cpp:25
+struct ExampleAttrInfo : public ParsedAttrInfo {
+  ExampleAttrInfo() {
+    // Set the kind to NoSemaHandlerAttribute to make sure clang doesn't assume
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It would be really handy for the example to show how to list subjects for the declaration attribute, as that's a very common need.


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Comment at: clang/examples/Attribute/Attribute.cpp:29
+    AttrKind = ParsedAttr::NoSemaHandlerAttribute;
+    // Can take an optional string argument.
+    OptArgs = 1;
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Nothing here suggests the argument must be a string. It would be ideal to show users how to list out arguments and their types.


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Comment at: clang/examples/Attribute/Attribute.cpp:32-33
+    // GNU-style __attribute__(("example")) and C++-style [[example]] supported.
+    Spellings.push_back({ParsedAttr::AS_GNU, "example"});
+    Spellings.push_back({ParsedAttr::AS_CXX11, "::example"});
+  }
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Showing how to have a vendor namespace would also be especially helpful.

As a point of design, I wonder if we should be documenting (or diagnosing?) attributes from plugins that are added to the clang vendor namespace, as that does not seem like something we want to encourage?


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Comment at: clang/examples/Attribute/Attribute.cpp:35
+  }
+  virtual bool handleDeclAttribute(Sema &S, Decl *D,
+                                   const ParsedAttr &Attr) const {
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It is unclear to me how a user would add an attribute that needs to follow the merge pattern we use in `mergeDeclAttribute()`.


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Comment at: clang/examples/Attribute/Attribute.cpp:53
+      } else {
+        S.Diag(ArgExpr->getExprLoc(), diag::err_attribute_argument_type)
+            << Attr.getAttrName() << AANT_ArgumentString;
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Do we have a way for plugin authors to introduce their own diagnostics, or are they limited to just what diagnostics we already provide?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D31343/new/

https://reviews.llvm.org/D31343