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//===- 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.
//
// This plugin is used by clang/test/Frontend/plugin-attribute tests.
//
//===----------------------------------------------------------------------===//
#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++/C2x-style [[example]] and
// [[plugin::example]] supported.
static constexpr Spelling S[] = {{ParsedAttr::AS_GNU, "example"},
{ParsedAttr::AS_C2x, "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", "");
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