[clang-tidy] Adding Fuchsia checker for virtual inheritance

Adds a check to the Fuchsia module to warn if classes are defined
with virtual inheritance.

See https://fuchsia.googlesource.com/zircon/+/master/docs/cxx.md for
reference.

Differential Revision: https://reviews.llvm.org/D40813

llvm-svn: 320841

clang-tools-extra/clang-tidy/fuchsia/CMakeLists.txt

@@ -3,6 +3,7 @@ set(LLVM_LINK_COMPONENTS support)
 add_clang_library(clangTidyFuchsiaModule
   DefaultArgumentsCheck.cpp
   FuchsiaTidyModule.cpp
+  VirtualInheritanceCheck.cpp
 
   LINK_LIBS
   clangAST

clang-tools-extra/clang-tidy/fuchsia/FuchsiaTidyModule.cpp

@@ -11,6 +11,7 @@
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
 #include "DefaultArgumentsCheck.h"
+#include "VirtualInheritanceCheck.h"
 
 using namespace clang::ast_matchers;
 
@@ -24,6 +25,8 @@ public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     CheckFactories.registerCheck<DefaultArgumentsCheck>(
         "fuchsia-default-arguments");
+    CheckFactories.registerCheck<VirtualInheritanceCheck>(
+        "fuchsia-virtual-inheritance");
   }
 };
 // Register the FuchsiaTidyModule using this statically initialized variable.

clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.cpp

@@ -0,0 +1,41 @@
+//===--- VirtualInheritanceCheck.cpp - clang-tidy--------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "VirtualInheritanceCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+
+AST_MATCHER(CXXRecordDecl, hasDirectVirtualBaseClass) {
+  if (!Node.hasDefinition()) return false;
+  if (!Node.getNumVBases()) return false;
+  for (const CXXBaseSpecifier &Base : Node.bases())
+    if (Base.isVirtual()) return true;
+  return false;
+}
+
+void VirtualInheritanceCheck::registerMatchers(MatchFinder *Finder) {
+  // Defining classes using direct virtual inheritance is disallowed.
+  Finder->addMatcher(cxxRecordDecl(hasDirectVirtualBaseClass()).bind("decl"),
+                     this);
+}
+
+void VirtualInheritanceCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *D = Result.Nodes.getNodeAs<CXXRecordDecl>("decl"))
+    diag(D->getLocStart(), "direct virtual inheritance is disallowed");
+}
+
+}  // namespace fuchsia
+}  // namespace tidy
+}  // namespace clang

clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.h

@@ -0,0 +1,35 @@
+//===--- VirtualInheritanceCheck.h - clang-tidy------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_VIRTUAL_INHERITANCE_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_VIRTUAL_INHERITANCE_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+
+/// Defining classes with virtual inheritance is disallowed.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/fuchsia-virtual-inheritance.html
+class VirtualInheritanceCheck : public ClangTidyCheck {
+ public:
+  VirtualInheritanceCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+}  // namespace fuchsia
+}  // namespace tidy
+}  // namespace clang
+
+#endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_VIRTUAL_INHERITANCE_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -135,6 +135,11 @@ Improvements to clang-tidy
 
   Warns if a function or method is declared or called with default arguments.
   
+- New `fuchsia-virtual-inheritance
+  <http://clang.llvm.org/extra/clang-tidy/checks/fuchsia-virtual-inheritance.html>`_ check
+
+  Warns if classes are defined with virtual inheritance.
+    
 - New `google-objc-avoid-throwing-exception
   <http://clang.llvm.org/extra/clang-tidy/checks/google-objc-avoid-throwing-exception.html>`_ check
 

clang-tools-extra/docs/clang-tidy/checks/fuchsia-virtual-inheritance.rst

@@ -0,0 +1,14 @@
+.. title:: clang-tidy - fuchsia-virtual-inheritance
+
+fuchsia-virtual-inheritance
+===========================
+
+Warns if classes are defined with virtual inheritance.
+
+For example, classes should not be defined with virtual inheritance:
+
+.. code-block:: c++
+
+  class B : public virtual A {};   // warning
+
+See the features disallowed in Fuchsia at https://fuchsia.googlesource.com/zircon/+/master/docs/cxx.md

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -69,6 +69,7 @@ Clang-Tidy Checks
    cppcoreguidelines-slicing
    cppcoreguidelines-special-member-functions
    fuchsia-default-arguments
+   fuchsia-virtual-inheritance
    google-build-explicit-make-pair
    google-build-namespaces
    google-build-using-namespace

clang-tools-extra/test/clang-tidy/fuchsia-virtual-inheritance.cpp

@@ -0,0 +1,42 @@
+// RUN: %check_clang_tidy %s fuchsia-virtual-inheritance %t
+
+class A {
+public:
+  A(int value) : val(value) {}
+
+  int do_A() { return val; }
+
+private:
+  int val;
+};
+
+class B : public virtual A {
+  // CHECK-MESSAGES: [[@LINE-1]]:1: warning: direct virtual inheritance is disallowed [fuchsia-virtual-inheritance]
+  // CHECK-NEXT: class B : public virtual A {
+public:
+  B() : A(0) {}
+  int do_B() { return 1 + do_A(); }
+};
+
+class C : public virtual A {
+  // CHECK-MESSAGES: [[@LINE-1]]:1: warning: direct virtual inheritance is disallowed [fuchsia-virtual-inheritance]
+  // CHECK-NEXT: class C : public virtual A {
+public:
+  C() : A(0) {}
+  int do_C() { return 2 + do_A(); }
+};
+
+class D : public B, public C {
+public:
+  D(int value) : A(value), B(), C() {}
+
+  int do_D() { return do_A() + do_B() + do_C(); }
+};
+
+int main() {
+  A *a = new A(0);
+  B *b = new B();
+  C *c = new C();
+  D *d = new D(0);
+  return 0;
+}