import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

media/webrtc/trunk/tools/clang/plugins/FindBadConstructs.cpp

@@ -0,0 +1,435 @@
+// Copyright (c) 2012 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.
+// - Non-annotated overriding virtual methods.
+// - Virtual methods with nonempty implementations in their headers.
+// - Classes that derive from base::RefCounted / base::RefCountedThreadSafe
+//   should have protected or private destructors.
+
+#include "clang/Frontend/FrontendPluginRegistry.h"
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/AST.h"
+#include "clang/AST/CXXInheritance.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;
+}
+
+// Returns the underlying Type for |type| by expanding typedefs and removing
+// any namespace qualifiers.
+const Type* UnwrapType(const Type* type) {
+  if (const ElaboratedType* elaborated = dyn_cast<ElaboratedType>(type))
+    return UnwrapType(elaborated->getNamedType().getTypePtr());
+  if (const TypedefType* typedefed = dyn_cast<TypedefType>(type))
+    return UnwrapType(typedefed->desugar().getTypePtr());
+  return type;
+}
+
+// Searches for constructs that we know we don't want in the Chromium code base.
+class FindBadConstructsConsumer : public ChromeClassTester {
+ public:
+  FindBadConstructsConsumer(CompilerInstance& instance,
+                            bool check_refcounted_dtors,
+                            bool check_virtuals_in_implementations)
+      : ChromeClassTester(instance),
+        check_refcounted_dtors_(check_refcounted_dtors),
+        check_virtuals_in_implementations_(check_virtuals_in_implementations) {
+  }
+
+  virtual void CheckChromeClass(SourceLocation record_location,
+                                CXXRecordDecl* record) {
+    bool implementation_file = InImplementationFile(record_location);
+
+    if (!implementation_file) {
+      // Only check for "heavy" constructors/destructors in header files;
+      // within implementation files, there is no performance cost.
+      CheckCtorDtorWeight(record_location, record);
+    }
+
+    if (!implementation_file || check_virtuals_in_implementations_) {
+      bool warn_on_inline_bodies = !implementation_file;
+
+      // Check that all virtual methods are marked accordingly with both
+      // virtual and OVERRIDE.
+      CheckVirtualMethods(record_location, record, warn_on_inline_bodies);
+    }
+
+    if (check_refcounted_dtors_)
+      CheckRefCountedDtors(record_location, record);
+  }
+
+ private:
+  bool check_refcounted_dtors_;
+  bool check_virtuals_in_implementations_;
+
+  // Returns true if |base| specifies one of the Chromium reference counted
+  // classes (base::RefCounted / base::RefCountedThreadSafe). |user_data| is
+  // ignored.
+  static bool IsRefCountedCallback(const CXXBaseSpecifier* base,
+                                   CXXBasePath& path,
+                                   void* user_data) {
+    FindBadConstructsConsumer* self =
+        static_cast<FindBadConstructsConsumer*>(user_data);
+
+    const TemplateSpecializationType* base_type =
+        dyn_cast<TemplateSpecializationType>(
+            UnwrapType(base->getType().getTypePtr()));
+    if (!base_type) {
+      // Base-most definition is not a template, so this cannot derive from
+      // base::RefCounted. However, it may still be possible to use with a
+      // scoped_refptr<> and support ref-counting, so this is not a perfect
+      // guarantee of safety.
+      return false;
+    }
+
+    TemplateName name = base_type->getTemplateName();
+    if (TemplateDecl* decl = name.getAsTemplateDecl()) {
+      std::string base_name = decl->getNameAsString();
+
+      // Check for both base::RefCounted and base::RefCountedThreadSafe.
+      if (base_name.compare(0, 10, "RefCounted") == 0 &&
+          self->GetNamespace(decl) == "base") {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  // Prints errors if the destructor of a RefCounted class is public.
+  void CheckRefCountedDtors(SourceLocation record_location,
+                            CXXRecordDecl* record) {
+    // Skip anonymous structs.
+    if (record->getIdentifier() == NULL)
+      return;
+
+    CXXBasePaths paths;
+    if (!record->lookupInBases(
+            &FindBadConstructsConsumer::IsRefCountedCallback, this, paths)) {
+      return;  // Class does not derive from a ref-counted base class.
+    }
+
+    if (!record->hasUserDeclaredDestructor()) {
+      emitWarning(
+          record_location,
+          "Classes that are ref-counted should have explicit "
+          "destructors that are protected or private.");
+    } else if (CXXDestructorDecl* dtor = record->getDestructor()) {
+      if (dtor->getAccess() == AS_public) {
+        emitWarning(
+            dtor->getInnerLocStart(),
+            "Classes that are ref-counted should not have "
+            "public destructors.");
+      }
+    }
+  }
+
+  // Prints errors if the constructor/destructor weight is too heavy.
+  void CheckCtorDtorWeight(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 an explicit out-of-line "
+                    "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()) {
+            if (it->isCopyConstructor() &&
+                !record->hasUserDeclaredCopyConstructor()) {
+              emitWarning(record_location,
+                          "Complex class/struct needs an explicit out-of-line "
+                          "copy constructor.");
+            } else {
+              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 an explicit out-of-line "
+            "destructor.");
+      } else if (CXXDestructorDecl* dtor = record->getDestructor()) {
+        if (dtor->hasInlineBody()) {
+          emitWarning(dtor->getInnerLocStart(),
+                      "Complex destructor has an inline body.");
+        }
+      }
+    }
+  }
+
+  void CheckVirtualMethod(const CXXMethodDecl* method,
+                          bool warn_on_inline_bodies) {
+    if (!method->isVirtual())
+      return;
+
+    if (!method->isVirtualAsWritten()) {
+      SourceLocation loc = method->getTypeSpecStartLoc();
+      if (isa<CXXDestructorDecl>(method))
+        loc = method->getInnerLocStart();
+      emitWarning(loc, "Overriding method must have \"virtual\" keyword.");
+    }
+
+    // Virtual methods should not have inline definitions beyond "{}". This
+    // only matters for header files.
+    if (warn_on_inline_bodies && method->hasBody() &&
+        method->hasInlineBody()) {
+      if (CompoundStmt* cs = dyn_cast<CompoundStmt>(method->getBody())) {
+        if (cs->size()) {
+          emitWarning(
+              cs->getLBracLoc(),
+              "virtual methods with non-empty bodies shouldn't be "
+              "declared inline.");
+        }
+      }
+    }
+  }
+
+  bool InTestingNamespace(const Decl* record) {
+    return GetNamespace(record).find("testing") != std::string::npos;
+  }
+
+  bool IsMethodInBannedNamespace(const CXXMethodDecl* method) {
+    if (InBannedNamespace(method))
+      return true;
+    for (CXXMethodDecl::method_iterator i = method->begin_overridden_methods();
+         i != method->end_overridden_methods();
+         ++i) {
+      const CXXMethodDecl* overridden = *i;
+      if (IsMethodInBannedNamespace(overridden))
+        return true;
+    }
+
+    return false;
+  }
+
+  void CheckOverriddenMethod(const CXXMethodDecl* method) {
+    if (!method->size_overridden_methods() || method->getAttr<OverrideAttr>())
+      return;
+
+    if (isa<CXXDestructorDecl>(method) || method->isPure())
+      return;
+
+    if (IsMethodInBannedNamespace(method))
+      return;
+
+    SourceLocation loc = method->getTypeSpecStartLoc();
+    emitWarning(loc, "Overriding method must be marked with OVERRIDE.");
+  }
+
+  // Makes sure there is a "virtual" keyword on virtual methods.
+  //
+  // 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(SourceLocation record_location,
+                           CXXRecordDecl* record,
+                           bool warn_on_inline_bodies) {
+    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() || isa<CXXConstructorDecl>(*it)) {
+        // Ignore constructors and assignment operators.
+      } else if (isa<CXXDestructorDecl>(*it) &&
+          !record->hasUserDeclaredDestructor()) {
+        // Ignore non-user-declared destructors.
+      } else {
+        CheckVirtualMethod(*it, warn_on_inline_bodies);
+        CheckOverriddenMethod(*it);
+      }
+    }
+  }
+
+  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 {
+ public:
+  FindBadConstructsAction()
+      : check_refcounted_dtors_(true),
+        check_virtuals_in_implementations_(true) {
+  }
+
+ protected:
+  // Overridden from PluginASTAction:
+  virtual ASTConsumer* CreateASTConsumer(CompilerInstance& instance,
+                                         llvm::StringRef ref) {
+    return new FindBadConstructsConsumer(
+        instance, check_refcounted_dtors_, check_virtuals_in_implementations_);
+  }
+
+  virtual bool ParseArgs(const CompilerInstance& instance,
+                         const std::vector<std::string>& args) {
+    bool parsed = true;
+
+    for (size_t i = 0; i < args.size() && parsed; ++i) {
+      if (args[i] == "skip-refcounted-dtors") {
+        check_refcounted_dtors_ = false;
+      } else if (args[i] == "skip-virtuals-in-implementations") {
+        check_virtuals_in_implementations_ = false;
+      } else {
+        parsed = false;
+        llvm::errs() << "Unknown argument: " << args[i] << "\n";
+      }
+    }
+
+    return parsed;
+  }
+
+ private:
+  bool check_refcounted_dtors_;
+  bool check_virtuals_in_implementations_;
+};
+
+}  // namespace
+
+static FrontendPluginRegistry::Add<FindBadConstructsAction>
+X("find-bad-constructs", "Finds bad C++ constructs");