tools/clang/plugins/FindBadConstructs.cpp - chromium/src.git - Git at Google

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 // This file defines a bunch of recurring problems in the Chromium C++ code.
 //
 // Checks that are implemented:
 // - Constructors/Destructors should not be inlined if they are of a complex
 //   class type.
 // - Missing "virtual" keywords on methods that should be virtual.
 // - Virtual methods with nonempty implementations in their headers.
 //
 // Things that are still TODO:
 // - Deriving from base::RefCounted and friends should mandate non-public
 //   destructors.

 #include "clang/Frontend/FrontendPluginRegistry.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/AST.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "llvm/Support/raw_ostream.h"

 #include "ChromeClassTester.h"

 using namespace clang;

 namespace {

 bool TypeHasNonTrivialDtor(const Type* type) {
   if (const CXXRecordDecl* cxx_r = type->getCXXRecordDeclForPointerType())
     return cxx_r->hasTrivialDestructor();

   return false;
 }

 // Searches for constructs that we know we don't want in the Chromium code base.
 class FindBadConstructsConsumer : public ChromeClassTester {
  public:
   FindBadConstructsConsumer(CompilerInstance& instance)
       : ChromeClassTester(instance) {}

   virtual void CheckChromeClass(const SourceLocation& record_location,
                                 CXXRecordDecl* record) {
     CheckCtorDtorWeight(record_location, record);
     CheckVirtualMethods(record_location, record);
   }

   // Prints errors if the constructor/destructor weight it too heavy.
   void CheckCtorDtorWeight(const SourceLocation& record_location,
                            CXXRecordDecl* record) {
     // We don't handle anonymous structs. If this record doesn't have a
     // name, it's of the form:
     //
     // struct {
     //   ...
     // } name_;
     if (record->getIdentifier() == NULL)
       return;

     // Count the number of templated base classes as a feature of whether the
     // destructor can be inlined.
     int templated_base_classes = 0;
     for (CXXRecordDecl::base_class_const_iterator it = record->bases_begin();
          it != record->bases_end(); ++it) {
       if (it->getTypeSourceInfo()->getTypeLoc().getTypeLocClass() ==
           TypeLoc::TemplateSpecialization) {
         ++templated_base_classes;
       }
     }

     // Count the number of trivial and non-trivial member variables.
     int trivial_member = 0;
     int non_trivial_member = 0;
     int templated_non_trivial_member = 0;
     for (RecordDecl::field_iterator it = record->field_begin();
          it != record->field_end(); ++it) {
       CountType(it->getType().getTypePtr(),
                 &trivial_member,
                 &non_trivial_member,
                 &templated_non_trivial_member);
     }

     // Check to see if we need to ban inlined/synthesized constructors. Note
     // that the cutoffs here are kind of arbitrary. Scores over 10 break.
     int dtor_score = 0;
     // Deriving from a templated base class shouldn't be enough to trigger
     // the ctor warning, but if you do *anything* else, it should.
     //
     // TODO(erg): This is motivated by templated base classes that don't have
     // any data members. Somehow detect when templated base classes have data
     // members and treat them differently.
     dtor_score += templated_base_classes * 9;
     // Instantiating a template is an insta-hit.
     dtor_score += templated_non_trivial_member * 10;
     // The fourth normal class member should trigger the warning.
     dtor_score += non_trivial_member * 3;

     int ctor_score = dtor_score;
     // You should be able to have 9 ints before we warn you.
     ctor_score += trivial_member;

     if (ctor_score >= 10) {
       if (!record->hasUserDeclaredConstructor()) {
         emitWarning(record_location,
                     "Complex class/struct needs a declared constructor.");
       } else {
         // Iterate across all the constructors in this file and yell if we
         // find one that tries to be inline.
         for (CXXRecordDecl::ctor_iterator it = record->ctor_begin();
              it != record->ctor_end(); ++it) {
           if (it->hasInlineBody()) {
             emitWarning(it->getInnerLocStart(),
                         "Complex constructor has an inlined body.");
           }
         }
       }
     }

     // The destructor side is equivalent except that we don't check for
     // trivial members; 20 ints don't need a destructor.
     if (dtor_score >= 10 && !record->hasTrivialDestructor()) {
       if (!record->hasUserDeclaredDestructor()) {
         emitWarning(record_location,
                     "Complex class/struct needs a declared destructor.");
       } else if (CXXDestructorDecl* dtor = record->getDestructor()) {
         if (dtor->hasInlineBody()) {
           emitWarning(dtor->getInnerLocStart(),
                       "Complex destructor has an inline body.");
         }
       }
     }
   }

   // Makes sure there is a "virtual" keyword on virtual methods and that there
   // are no inline function bodies on them (but "{}" is allowed).
   //
   // Gmock objects trigger these for each MOCK_BLAH() macro used. So we have a
   // trick to get around that. If a class has member variables whose types are
   // in the "testing" namespace (which is how gmock works behind the scenes),
   // there's a really high chance we won't care about these errors
   void CheckVirtualMethods(const SourceLocation& record_location,
                            CXXRecordDecl* record) {
     for (CXXRecordDecl::field_iterator it = record->field_begin();
          it != record->field_end(); ++it) {
       CXXRecordDecl* record_type =
           it->getTypeSourceInfo()->getTypeLoc().getTypePtr()->
           getAsCXXRecordDecl();
       if (record_type) {
         if (InTestingNamespace(record_type)) {
           return;
         }
       }
     }

     for (CXXRecordDecl::method_iterator it = record->method_begin();
          it != record->method_end(); ++it) {
       if (it->isCopyAssignmentOperator() ||
           dyn_cast<CXXConstructorDecl>(*it)) {
         // Ignore constructors and assignment operators.
       } else if (dyn_cast<CXXDestructorDecl>(*it)) {
         // TODO: I'd love to handle this case, but
         // CXXDestructorDecl::isImplicitlyDefined() asserts if I call it
         // here, and against my better judgment, I don't want to *always*
         // disallow implicit destructors.
       } else {
         if (it->isVirtual() && !it->isVirtualAsWritten()) {
           emitWarning(it->getTypeSpecStartLoc(),
                       "Overridden method must have \"virtual\" keyword.");
         }

         // Virtual methods should not have inline definitions beyond "{}".
         if (it->isVirtual() && it->hasBody() && it->hasInlineBody()) {
           if (CompoundStmt* cs = dyn_cast<CompoundStmt>(it->getBody())) {
             if (cs->size()) {
               emitWarning(
                   cs->getLBracLoc(),
                   "virtual methods with non-empty bodies shouldn't be "
                   "declared inline.");
             }
           }
         }
       }
     }
   }

   void CountType(const Type* type,
                  int* trivial_member,
                  int* non_trivial_member,
                  int* templated_non_trivial_member) {
     switch (type->getTypeClass()) {
       case Type::Record: {
         // Simplifying; the whole class isn't trivial if the dtor is, but
         // we use this as a signal about complexity.
         if (TypeHasNonTrivialDtor(type))
           (*trivial_member)++;
         else
           (*non_trivial_member)++;
         break;
       }
       case Type::TemplateSpecialization: {
         TemplateName name =
             dyn_cast<TemplateSpecializationType>(type)->getTemplateName();
         bool whitelisted_template = false;

         // HACK: I'm at a loss about how to get the syntax checker to get
         // whether a template is exterened or not. For the first pass here,
         // just do retarded string comparisons.
         if (TemplateDecl* decl = name.getAsTemplateDecl()) {
           std::string base_name = decl->getNameAsString();
           if (base_name == "basic_string")
             whitelisted_template = true;
         }

         if (whitelisted_template)
           (*non_trivial_member)++;
         else
           (*templated_non_trivial_member)++;
         break;
       }
       case Type::Elaborated: {
         CountType(
             dyn_cast<ElaboratedType>(type)->getNamedType().getTypePtr(),
             trivial_member, non_trivial_member, templated_non_trivial_member);
         break;
       }
       case Type::Typedef: {
         while (const TypedefType *TT = dyn_cast<TypedefType>(type)) {
           type = TT->getDecl()->getUnderlyingType().getTypePtr();
         }
         CountType(type, trivial_member, non_trivial_member,
                   templated_non_trivial_member);
         break;
       }
       default: {
         // Stupid assumption: anything we see that isn't the above is one of
         // the 20 integer types.
         (*trivial_member)++;
         break;
       }
     }
   }
 };

 class FindBadConstructsAction : public PluginASTAction {
  protected:
   ASTConsumer* CreateASTConsumer(CompilerInstance &CI, llvm::StringRef ref) {
     return new FindBadConstructsConsumer(CI);
   }

   bool ParseArgs(const CompilerInstance &CI,
                  const std::vector<std::string>& args) {
     // We don't take any additional arguments here.
     return true;
   }
 };

 }  // namespace

 static FrontendPluginRegistry::Add<FindBadConstructsAction>
 X("find-bad-constructs", "Finds bad C++ constructs");
	// Copyright (c) 2011 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	// This file defines a bunch of recurring problems in the Chromium C++ code.
	//
	// Checks that are implemented:
	// - Constructors/Destructors should not be inlined if they are of a complex
	// class type.
	// - Missing "virtual" keywords on methods that should be virtual.
	// - Virtual methods with nonempty implementations in their headers.
	//
	// Things that are still TODO:
	// - Deriving from base::RefCounted and friends should mandate non-public
	// destructors.

	#include "clang/Frontend/FrontendPluginRegistry.h"
	#include "clang/AST/ASTConsumer.h"
	#include "clang/AST/AST.h"
	#include "clang/AST/TypeLoc.h"
	#include "clang/Basic/SourceManager.h"
	#include "clang/Frontend/CompilerInstance.h"
	#include "llvm/Support/raw_ostream.h"

	#include "ChromeClassTester.h"

	using namespace clang;

	namespace {

	bool TypeHasNonTrivialDtor(const Type* type) {
	if (const CXXRecordDecl* cxx_r = type->getCXXRecordDeclForPointerType())
	return cxx_r->hasTrivialDestructor();

	return false;
	}

	// Searches for constructs that we know we don't want in the Chromium code base.
	class FindBadConstructsConsumer : public ChromeClassTester {
	public:
	FindBadConstructsConsumer(CompilerInstance& instance)
	: ChromeClassTester(instance) {}

	virtual void CheckChromeClass(const SourceLocation& record_location,
	CXXRecordDecl* record) {
	CheckCtorDtorWeight(record_location, record);
	CheckVirtualMethods(record_location, record);
	}

	// Prints errors if the constructor/destructor weight it too heavy.
	void CheckCtorDtorWeight(const SourceLocation& record_location,
	CXXRecordDecl* record) {
	// We don't handle anonymous structs. If this record doesn't have a
	// name, it's of the form:
	//
	// struct {
	// ...
	// } name_;
	if (record->getIdentifier() == NULL)
	return;

	// Count the number of templated base classes as a feature of whether the
	// destructor can be inlined.
	int templated_base_classes = 0;
	for (CXXRecordDecl::base_class_const_iterator it = record->bases_begin();
	it != record->bases_end(); ++it) {
	if (it->getTypeSourceInfo()->getTypeLoc().getTypeLocClass() ==
	TypeLoc::TemplateSpecialization) {
	++templated_base_classes;
	}
	}

	// Count the number of trivial and non-trivial member variables.
	int trivial_member = 0;
	int non_trivial_member = 0;
	int templated_non_trivial_member = 0;
	for (RecordDecl::field_iterator it = record->field_begin();
	it != record->field_end(); ++it) {
	CountType(it->getType().getTypePtr(),
	&trivial_member,
	&non_trivial_member,
	&templated_non_trivial_member);
	}

	// Check to see if we need to ban inlined/synthesized constructors. Note
	// that the cutoffs here are kind of arbitrary. Scores over 10 break.
	int dtor_score = 0;
	// Deriving from a templated base class shouldn't be enough to trigger
	// the ctor warning, but if you do anything else, it should.
	//
	// TODO(erg): This is motivated by templated base classes that don't have
	// any data members. Somehow detect when templated base classes have data
	// members and treat them differently.
	dtor_score += templated_base_classes * 9;
	// Instantiating a template is an insta-hit.
	dtor_score += templated_non_trivial_member * 10;
	// The fourth normal class member should trigger the warning.
	dtor_score += non_trivial_member * 3;

	int ctor_score = dtor_score;
	// You should be able to have 9 ints before we warn you.
	ctor_score += trivial_member;

	if (ctor_score >= 10) {
	if (!record->hasUserDeclaredConstructor()) {
	emitWarning(record_location,
	"Complex class/struct needs a declared constructor.");
	} else {
	// Iterate across all the constructors in this file and yell if we
	// find one that tries to be inline.
	for (CXXRecordDecl::ctor_iterator it = record->ctor_begin();
	it != record->ctor_end(); ++it) {
	if (it->hasInlineBody()) {
	emitWarning(it->getInnerLocStart(),
	"Complex constructor has an inlined body.");
	}
	}
	}
	}

	// The destructor side is equivalent except that we don't check for
	// trivial members; 20 ints don't need a destructor.
	if (dtor_score >= 10 && !record->hasTrivialDestructor()) {
	if (!record->hasUserDeclaredDestructor()) {
	emitWarning(record_location,
	"Complex class/struct needs a declared destructor.");
	} else if (CXXDestructorDecl* dtor = record->getDestructor()) {
	if (dtor->hasInlineBody()) {
	emitWarning(dtor->getInnerLocStart(),
	"Complex destructor has an inline body.");
	}
	}
	}
	}

	// Makes sure there is a "virtual" keyword on virtual methods and that there
	// are no inline function bodies on them (but "{}" is allowed).
	//
	// Gmock objects trigger these for each MOCK_BLAH() macro used. So we have a
	// trick to get around that. If a class has member variables whose types are
	// in the "testing" namespace (which is how gmock works behind the scenes),
	// there's a really high chance we won't care about these errors
	void CheckVirtualMethods(const SourceLocation& record_location,
	CXXRecordDecl* record) {
	for (CXXRecordDecl::field_iterator it = record->field_begin();
	it != record->field_end(); ++it) {
	CXXRecordDecl* record_type =
	it->getTypeSourceInfo()->getTypeLoc().getTypePtr()->
	getAsCXXRecordDecl();
	if (record_type) {
	if (InTestingNamespace(record_type)) {
	return;
	}
	}
	}

	for (CXXRecordDecl::method_iterator it = record->method_begin();
	it != record->method_end(); ++it) {
	if (it->isCopyAssignmentOperator() \|\|
	dyn_cast<CXXConstructorDecl>(*it)) {
	// Ignore constructors and assignment operators.
	} else if (dyn_cast<CXXDestructorDecl>(*it)) {
	// TODO: I'd love to handle this case, but
	// CXXDestructorDecl::isImplicitlyDefined() asserts if I call it
	// here, and against my better judgment, I don't want to always
	// disallow implicit destructors.
	} else {
	if (it->isVirtual() && !it->isVirtualAsWritten()) {
	emitWarning(it->getTypeSpecStartLoc(),
	"Overridden method must have \"virtual\" keyword.");
	}

	// Virtual methods should not have inline definitions beyond "{}".
	if (it->isVirtual() && it->hasBody() && it->hasInlineBody()) {
	if (CompoundStmt* cs = dyn_cast<CompoundStmt>(it->getBody())) {
	if (cs->size()) {
	emitWarning(
	cs->getLBracLoc(),
	"virtual methods with non-empty bodies shouldn't be "
	"declared inline.");
	}
	}
	}
	}
	}
	}

	void CountType(const Type* type,
	int* trivial_member,
	int* non_trivial_member,
	int* templated_non_trivial_member) {
	switch (type->getTypeClass()) {
	case Type::Record: {
	// Simplifying; the whole class isn't trivial if the dtor is, but
	// we use this as a signal about complexity.
	if (TypeHasNonTrivialDtor(type))
	(*trivial_member)++;
	else
	(*non_trivial_member)++;
	break;
	}
	case Type::TemplateSpecialization: {
	TemplateName name =
	dyn_cast<TemplateSpecializationType>(type)->getTemplateName();
	bool whitelisted_template = false;

	// HACK: I'm at a loss about how to get the syntax checker to get
	// whether a template is exterened or not. For the first pass here,
	// just do retarded string comparisons.
	if (TemplateDecl* decl = name.getAsTemplateDecl()) {
	std::string base_name = decl->getNameAsString();
	if (base_name == "basic_string")
	whitelisted_template = true;
	}

	if (whitelisted_template)
	(*non_trivial_member)++;
	else
	(*templated_non_trivial_member)++;
	break;
	}
	case Type::Elaborated: {
	CountType(
	dyn_cast<ElaboratedType>(type)->getNamedType().getTypePtr(),
	trivial_member, non_trivial_member, templated_non_trivial_member);
	break;
	}
	case Type::Typedef: {
	while (const TypedefType *TT = dyn_cast<TypedefType>(type)) {
	type = TT->getDecl()->getUnderlyingType().getTypePtr();
	}
	CountType(type, trivial_member, non_trivial_member,
	templated_non_trivial_member);
	break;
	}
	default: {
	// Stupid assumption: anything we see that isn't the above is one of
	// the 20 integer types.
	(*trivial_member)++;
	break;
	}
	}
	}
	};

	class FindBadConstructsAction : public PluginASTAction {
	protected:
	ASTConsumer* CreateASTConsumer(CompilerInstance &CI, llvm::StringRef ref) {
	return new FindBadConstructsConsumer(CI);
	}

	bool ParseArgs(const CompilerInstance &CI,
	const std::vector<std::string>& args) {
	// We don't take any additional arguments here.
	return true;
	}
	};

	} // namespace

	static FrontendPluginRegistry::Add<FindBadConstructsAction>
	X("find-bad-constructs", "Finds bad C++ constructs");