--- /dev/null
+//===- 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 an optional string argument (the check that the argument
+ // actually is a string happens in handleDeclAttribute).
+ OptArgs = 1;
+ // GNU-style __attribute__(("example")) and C++-style [[example]] and
+ // [[plugin::example]] supported.
+ Spellings.push_back({ParsedAttr::AS_GNU, "example"});
+ Spellings.push_back({ParsedAttr::AS_CXX11, "example"});
+ Spellings.push_back({ParsedAttr::AS_CXX11, "plugin::example"});
+ }
+
+ 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;
+ }
+ // Check if we have an optional string argument.
+ StringRef Str = "";
+ if (Attr.getNumArgs() > 0) {
+ Expr *ArgExpr = Attr.getArgAsExpr(0);
+ StringLiteral *Literal =
+ dyn_cast<StringLiteral>(ArgExpr->IgnoreParenCasts());
+ if (Literal) {
+ Str = Literal->getString();
+ } else {
+ S.Diag(ArgExpr->getExprLoc(), diag::err_attribute_argument_type)
+ << Attr.getAttrName() << AANT_ArgumentString;
+ return AttributeNotApplied;
+ }
+ }
+ // Attach an annotate attribute to the Decl.
+ D->addAttr(AnnotateAttr::Create(S.Context, "example(" + Str.str() + ")",
+ Attr.getRange()));
+ return AttributeApplied;
+ }
+};
+
+} // namespace
+
+static ParsedAttrInfoRegistry::Add<ExampleAttrInfo> X("example", "");
--- /dev/null
+// RUN: %clang -fplugin=%llvmshlibdir/Attribute%pluginext -emit-llvm -S %s -o - 2>&1 | FileCheck %s --check-prefix=ATTRIBUTE
+// RUN: not %clang -fplugin=%llvmshlibdir/Attribute%pluginext -emit-llvm -DBAD_ATTRIBUTE -S %s -o - 2>&1 | FileCheck %s --check-prefix=BADATTRIBUTE
+// REQUIRES: plugins, examples
+
+void fn1a() __attribute__((example)) { }
+[[example]] void fn1b() { }
+[[plugin::example]] void fn1c() { }
+void fn2() __attribute__((example("somestring"))) { }
+// ATTRIBUTE: warning: 'example' attribute only applies to functions
+int var1 __attribute__((example("otherstring"))) = 1;
+
+// ATTRIBUTE: [[STR1_VAR:@.+]] = private unnamed_addr constant [10 x i8] c"example()\00"
+// ATTRIBUTE: [[STR2_VAR:@.+]] = private unnamed_addr constant [20 x i8] c"example(somestring)\00"
+// ATTRIBUTE: @llvm.global.annotations = {{.*}}@{{.*}}fn1a{{.*}}[[STR1_VAR]]{{.*}}@{{.*}}fn1b{{.*}}[[STR1_VAR]]{{.*}}@{{.*}}fn1c{{.*}}[[STR1_VAR]]{{.*}}@{{.*}}fn2{{.*}}[[STR2_VAR]]
+
+#ifdef BAD_ATTRIBUTE
+class Example {
+ // BADATTRIBUTE: error: 'example' attribute only allowed at file scope
+ void __attribute__((example)) fn3();
+};
+// BADATTRIBUTE: error: 'example' attribute requires a string
+void fn4() __attribute__((example(123))) { }
+// BADATTRIBUTE: error: 'example' attribute takes no more than 1 argument
+void fn5() __attribute__((example("a","b"))) { }
+#endif