1 //===- Attribute.cpp ------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Example clang plugin which adds an an annotation to file-scope declarations
10 // with the 'example' attribute.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/AST/ASTContext.h"
15 #include "clang/AST/Attr.h"
16 #include "clang/Sema/ParsedAttr.h"
17 #include "clang/Sema/Sema.h"
18 #include "clang/Sema/SemaDiagnostic.h"
19 #include "llvm/IR/Attributes.h"
20 using namespace clang;
21 
22 namespace {
23 
24 struct ExampleAttrInfo : public ParsedAttrInfo {
ExampleAttrInfo__anonbca32ac70111::ExampleAttrInfo25   ExampleAttrInfo() {
26     // Can take an optional string argument (the check that the argument
27     // actually is a string happens in handleDeclAttribute).
28     OptArgs = 1;
29     // GNU-style __attribute__(("example")) and C++-style [[example]] and
30     // [[plugin::example]] supported.
31     static constexpr Spelling S[] = {{ParsedAttr::AS_GNU, "example"},
32                                      {ParsedAttr::AS_CXX11, "example"},
33                                      {ParsedAttr::AS_CXX11, "plugin::example"}};
34     Spellings = S;
35   }
36 
diagAppertainsToDecl__anonbca32ac70111::ExampleAttrInfo37   bool diagAppertainsToDecl(Sema &S, const ParsedAttr &Attr,
38                             const Decl *D) const override {
39     // This attribute appertains to functions only.
40     if (!isa<FunctionDecl>(D)) {
41       S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type_str)
42         << Attr << "functions";
43       return false;
44     }
45     return true;
46   }
47 
handleDeclAttribute__anonbca32ac70111::ExampleAttrInfo48   AttrHandling handleDeclAttribute(Sema &S, Decl *D,
49                                    const ParsedAttr &Attr) const override {
50     // Check if the decl is at file scope.
51     if (!D->getDeclContext()->isFileContext()) {
52       unsigned ID = S.getDiagnostics().getCustomDiagID(
53           DiagnosticsEngine::Error,
54           "'example' attribute only allowed at file scope");
55       S.Diag(Attr.getLoc(), ID);
56       return AttributeNotApplied;
57     }
58     // Check if we have an optional string argument.
59     StringRef Str = "";
60     if (Attr.getNumArgs() > 0) {
61       Expr *ArgExpr = Attr.getArgAsExpr(0);
62       StringLiteral *Literal =
63           dyn_cast<StringLiteral>(ArgExpr->IgnoreParenCasts());
64       if (Literal) {
65         Str = Literal->getString();
66       } else {
67         S.Diag(ArgExpr->getExprLoc(), diag::err_attribute_argument_type)
68             << Attr.getAttrName() << AANT_ArgumentString;
69         return AttributeNotApplied;
70       }
71     }
72     // Attach an annotate attribute to the Decl.
73     D->addAttr(AnnotateAttr::Create(S.Context, "example(" + Str.str() + ")",
74                                     Attr.getRange()));
75     return AttributeApplied;
76   }
77 };
78 
79 } // namespace
80 
81 static ParsedAttrInfoRegistry::Add<ExampleAttrInfo> X("example", "");
82