PureNoexcept.cpp

/*
 * clang plugin which emits warnings for functions which should have a
 * "noexcept" specification.
 *
 * Author: Max Kellermann <[email protected]>
 *
 * This file is distributed under the University of Illinois Open Source
 * License.
 */

#include "clang/Frontend/FrontendPluginRegistry.h"
#include "clang/AST/AST.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Sema/Sema.h"
#include "llvm/Support/raw_ostream.h"

using namespace clang;

namespace {

bool
IsPure(const Decl &d)
{
	return d.hasAttr<PureAttr>() || d.hasAttr<ConstAttr>();
}

bool
IsNoexcept(const FunctionType &t)
{
	if (const auto *p = dyn_cast<FunctionProtoType>(&t))
		return isNoexceptExceptionSpec(p->getExceptionSpecType());
	return false;
}

bool
IsNoexcept(const QualType &qt)
{
	const auto *t = qt.getTypePtr();
	if (const auto *ft = dyn_cast<FunctionType>(t))
		return IsNoexcept(*ft);
	return false;
}

bool
IsNoexcept(const ValueDecl &d)
{
	return IsNoexcept(d.getType());
}

class PureNoexceptConsumer : public ASTConsumer {
	CompilerInstance &Instance;

public:
	explicit PureNoexceptConsumer(CompilerInstance &Instance)
		: Instance(Instance) {}

	bool HandleTopLevelDecl(DeclGroupRef DG) override {
		auto &diag = Instance.getDiagnostics();

		for (DeclGroupRef::iterator i = DG.begin(), e = DG.end(); i != e; ++i) {
			const Decl *D = *i;
			if (const FunctionDecl *ND = dyn_cast<FunctionDecl>(D))
				if (IsPure(*ND) && !IsNoexcept(*ND)) {
					const auto ID = diag.getCustomDiagID(clang::DiagnosticsEngine::Warning,
									     "'pure' function without 'noexcept'");
					diag.Report(ND->getLocation(), ID);
				}
		}

		return true;
	}
};

class PureNoexceptAction : public PluginASTAction {
protected:
	std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
						       llvm::StringRef) override {
		return llvm::make_unique<PureNoexceptConsumer>(CI);
	}

	bool ParseArgs(const CompilerInstance &CI,
		       const std::vector<std::string> &args) override {
		if (!args.empty()) {
			llvm::errs() << "This plugin has no arguments\n";
			return false;
		}

		return true;
	}

};

}

static FrontendPluginRegistry::Add<PureNoexceptAction>
X("pure-noexcept", "Show missing 'noexcept' attributes for 'pure' and 'const' functions");