| //===- Attribute.cpp ------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Example clang plugin which adds an an annotation to file-scope declarations |
| // with the 'example' attribute. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/Attr.h" |
| #include "clang/Sema/ParsedAttr.h" |
| #include "clang/Sema/Sema.h" |
| #include "clang/Sema/SemaDiagnostic.h" |
| #include "llvm/IR/Attributes.h" |
| using namespace clang; |
| |
| namespace { |
| |
| struct ExampleAttrInfo : public ParsedAttrInfo { |
| ExampleAttrInfo() { |
| // Can take up to 15 optional arguments, to emulate accepting a variadic |
| // number of arguments. This just illustrates how many arguments a |
| // `ParsedAttrInfo` can hold, we will not use that much in this example. |
| OptArgs = 15; |
| // GNU-style __attribute__(("example")) and C++-style [[example]] and |
| // [[plugin::example]] supported. |
| static constexpr Spelling S[] = {{ParsedAttr::AS_GNU, "example"}, |
| {ParsedAttr::AS_CXX11, "example"}, |
| {ParsedAttr::AS_CXX11, "plugin::example"}}; |
| Spellings = S; |
| } |
| |
| bool diagAppertainsToDecl(Sema &S, const ParsedAttr &Attr, |
| const Decl *D) const override { |
| // This attribute appertains to functions only. |
| if (!isa<FunctionDecl>(D)) { |
| S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type_str) |
| << Attr << "functions"; |
| return false; |
| } |
| return true; |
| } |
| |
| AttrHandling handleDeclAttribute(Sema &S, Decl *D, |
| const ParsedAttr &Attr) const override { |
| // Check if the decl is at file scope. |
| if (!D->getDeclContext()->isFileContext()) { |
| unsigned ID = S.getDiagnostics().getCustomDiagID( |
| DiagnosticsEngine::Error, |
| "'example' attribute only allowed at file scope"); |
| S.Diag(Attr.getLoc(), ID); |
| return AttributeNotApplied; |
| } |
| // We make some rules here: |
| // 1. Only accept at most 3 arguments here. |
| // 2. The first argument must be a string literal if it exists. |
| if (Attr.getNumArgs() > 3) { |
| unsigned ID = S.getDiagnostics().getCustomDiagID( |
| DiagnosticsEngine::Error, |
| "'example' attribute only accepts at most three arguments"); |
| S.Diag(Attr.getLoc(), ID); |
| return AttributeNotApplied; |
| } |
| // If there are arguments, the first argument should be a string literal. |
| if (Attr.getNumArgs() > 0) { |
| auto *Arg0 = Attr.getArgAsExpr(0); |
| StringLiteral *Literal = |
| dyn_cast<StringLiteral>(Arg0->IgnoreParenCasts()); |
| if (!Literal) { |
| unsigned ID = S.getDiagnostics().getCustomDiagID( |
| DiagnosticsEngine::Error, "first argument to the 'example' " |
| "attribute must be a string literal"); |
| S.Diag(Attr.getLoc(), ID); |
| return AttributeNotApplied; |
| } |
| SmallVector<Expr *, 16> ArgsBuf; |
| for (unsigned i = 0; i < Attr.getNumArgs(); i++) { |
| ArgsBuf.push_back(Attr.getArgAsExpr(i)); |
| } |
| D->addAttr(AnnotateAttr::Create(S.Context, "example", ArgsBuf.data(), |
| ArgsBuf.size(), Attr.getRange())); |
| } else { |
| // Attach an annotate attribute to the Decl. |
| D->addAttr(AnnotateAttr::Create(S.Context, "example", nullptr, 0, |
| Attr.getRange())); |
| } |
| return AttributeApplied; |
| } |
| }; |
| |
| } // namespace |
| |
| static ParsedAttrInfoRegistry::Add<ExampleAttrInfo> X("example", ""); |