Update attribute example to fit the new Annotation API

[psionic12]

Summary

Since AnnotationAttr can add extra arguments
now, update Attribute plugin example to fit this API
to make this example compiled.

[psionic12]

clang/examples/Attribute/Attribute.cpp

59

AnnotationAttr is used as an extra information in attribute plugin designs. Usually after handling the customized attribute, coders will add an AnnotationAttr into the AST, for later use.

Before the new API released, create an AnnotationAttr is not very hard.

But now AnnotationAttr accepts a StringLiteralExpr as it's first argument, in order to do the same thing I mentioned above, we have to create an StringLiteralExpr from nowhere, which looks not very elegant to me.

[Tyker]

I recently made it much easier to create AnnotationAttr in this context with https://reviews.llvm.org/rGd093401a2617d3c46aaed9eeaecf877e3ae1a9f1.

clang/examples/Attribute/Attribute.cpp

AttrHandling handleDeclAttribute(Sema &S, Decl *D,
     // 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;
-      }
+
+    // First we have to create an `StringLiteralExpr`.
+    StringRef AnnotationString = "example";
+    QualType StrTy = S.Context.getConstantArrayType(
+        S.Context.adjustStringLiteralBaseType(S.Context.CharTy.withConst()),
+        llvm::APInt(32, AnnotationString.size()), nullptr, ArrayType::Normal,
+        0);
+    const auto AnnotationStringLoc = Attr.getLoc();
+    auto *StringExpr =
+        StringLiteral::Create(S.Context, AnnotationString, StringLiteral::Ascii,
+                              /*Pascal*/ false, StrTy, &AnnotationStringLoc, 1);
+
+    llvm::SmallVector<Expr *, 4> Args;
+    Args.reserve(Attr.getNumArgs() + 1);
+
+    // Add the `StringLiteralExpr` as the first argument to an `AnnotationAttr`
+    Args.push_back(StringExpr);
+    for (unsigned Idx = 1; Idx < Attr.getNumArgs(); Idx++) {
+      Args.push_back(Attr.getArgAsExpr(Idx));
     }
+
     // Attach an annotate attribute to the Decl.
-    D->addAttr(AnnotateAttr::Create(S.Context, "example(" + Str.str() + ")",
-                                    Attr.getRange()));
+    S.AddAnnotationAttr(D, {Attr.getRange()}, AnnotationString, Args);
     return AttributeApplied;
   }
 };
 
 } // namespace
 
 static ParsedAttrInfoRegistry::Add<ExampleAttrInfo> X("example", "");

clang/test/Frontend/plugin-attribute.cpp

 // 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
+// ATTRIBUTE: warning: 'example' attribute only applies to functions [-Wignored-attributes]
 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]]
+// ATTRIBUTE: [[STR1_VAR:@.+]] = private unnamed_addr constant [8 x i8] c"example\00", section "llvm.metadata"
+// ATTRIBUTE: @llvm.global.annotations = {{.*}}@{{.*}}fn1a{{.*}}[[STR1_VAR]]{{.*}}@{{.*}}fn1b{{.*}}[[STR1_VAR]]{{.*}}@{{.*}}fn1c{{.*}}[[STR1_VAR]]{{.*}}@{{.*}}fn2{{.*}}
 
 #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