//===- 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", ""); |