[clang-tidy] Adding Fuchsia checker for statically constructed objects

Adds a check to the Fuchsia module to warn if statically-stored objects
are created, unless constructed with `constexpr`.

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

Differential Revision: https://reviews.llvm.org/D41546

llvm-svn: 322310

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

@@ -4,6 +4,7 @@ add_clang_library(clangTidyFuchsiaModule
   DefaultArgumentsCheck.cpp
   FuchsiaTidyModule.cpp
   OverloadedOperatorCheck.cpp
+  StaticallyConstructedObjectsCheck.cpp
   VirtualInheritanceCheck.cpp
 
   LINK_LIBS

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

@@ -12,6 +12,7 @@
 #include "../ClangTidyModuleRegistry.h"
 #include "DefaultArgumentsCheck.h"
 #include "OverloadedOperatorCheck.h"
+#include "StaticallyConstructedObjectsCheck.h"
 #include "VirtualInheritanceCheck.h"
 
 using namespace clang::ast_matchers;
@@ -28,6 +29,8 @@ public:
         "fuchsia-default-arguments");
     CheckFactories.registerCheck<OverloadedOperatorCheck>(
         "fuchsia-overloaded-operator");
+    CheckFactories.registerCheck<StaticallyConstructedObjectsCheck>(
+        "fuchsia-statically-constructed-objects");
     CheckFactories.registerCheck<VirtualInheritanceCheck>(
         "fuchsia-virtual-inheritance");
   }

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

@@ -0,0 +1,58 @@
+//===--- StaticallyConstructedObjectsCheck.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 "StaticallyConstructedObjectsCheck.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+  
+AST_MATCHER(Expr, isConstantInitializer) {
+  return Node.isConstantInitializer(Finder->getASTContext(), false);
+}
+
+AST_MATCHER(VarDecl, isGlobalStatic) {
+  return Node.getStorageDuration() == SD_Static && !Node.isLocalVarDecl();
+}
+  
+void StaticallyConstructedObjectsCheck::registerMatchers(MatchFinder *Finder) {
+  // Constructing global, non-trivial objects with static storage is
+  // disallowed, unless the object is statically initialized with a constexpr 
+  // constructor or has no explicit constructor.
+
+  // Constexpr requires C++11 or later.
+  if (!getLangOpts().CPlusPlus11)
+    return;
+
+  Finder->addMatcher(
+      varDecl(allOf(
+                  // Match global, statically stored objects...
+                  isGlobalStatic(),
+                  // ... that have C++ constructors...
+                  hasDescendant(cxxConstructExpr(unless(allOf(
+                      // ... unless it is constexpr ...
+                      hasDeclaration(cxxConstructorDecl(isConstexpr())),
+                      // ... and is statically initialized.
+                      isConstantInitializer()))))))
+          .bind("decl"),
+      this);
+}
+
+void StaticallyConstructedObjectsCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  if (const auto *D = Result.Nodes.getNodeAs<VarDecl>("decl"))
+    diag(D->getLocStart(), "static objects are disallowed; if possible, use a "
+                           "constexpr constructor instead");
+}
+
+} // namespace fuchsia
+} // namespace tidy
+} // namespace clang

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

@@ -0,0 +1,37 @@
+//===--- StaticallyConstructedObjectsCheck.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_STATICALLY_CONSTRUCTED_OBJECTS_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_STATICALLY_CONSTRUCTED_OBJECTS_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+
+/// Constructing global, non-trivial objects with static storage is
+/// disallowed, unless the object is statically initialized with a constexpr 
+/// constructor or has no explicit constructor.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/fuchsia-statically-constructed-objects.html
+class StaticallyConstructedObjectsCheck : public ClangTidyCheck {
+public:
+  StaticallyConstructedObjectsCheck(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_STATICALLY_CONSTRUCTED_OBJECTS_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -57,7 +57,12 @@ The improvements are...
 Improvements to clang-tidy
 --------------------------
 
-- ...
+- New `fuchsia-statically-constructed-objects
+  <http://clang.llvm.org/extra/clang-tidy/checks/fuchsia-statically-constructed-objects.html>`_ check
+
+  Warns if global, non-trivial objects with static storage are constructed, unless the 
+  object is statically initialized with a ``constexpr`` constructor or has no 
+  explicit constructor.
 
 Improvements to include-fixer
 -----------------------------

clang-tools-extra/docs/clang-tidy/checks/fuchsia-statically-constructed-objects.rst

@@ -0,0 +1,43 @@
+.. title:: clang-tidy - fuchsia-statically-constructed-objects
+
+fuchsia-statically-constructed-objects
+======================================
+
+Warns if global, non-trivial objects with static storage are constructed, unless 
+the object is statically initialized with a ``constexpr`` constructor or has no 
+explicit constructor.
+
+For example:
+
+.. code-block:: c++
+
+  class A {};
+
+  class B {
+  public:
+    B(int Val) : Val(Val) {}
+  private:
+    int Val;
+  };
+
+  class C {
+  public:
+    C(int Val) : Val(Val) {}
+    constexpr C() : Val(0) {}
+
+  private:
+    int Val;
+  };
+
+  static A a;         // No warning, as there is no explicit constructor
+  static C c(0);      // No warning, as constructor is constexpr
+
+  static B b(0);      // Warning, as constructor is not constexpr
+  static C c2(0, 1);  // Warning, as constructor is not constexpr
+  
+  static int i;       // No warning, as it is trivial
+  
+  extern int get_i();
+  static C(get_i())   // Warning, as the constructor is dynamically initialized
+
+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

@@ -70,6 +70,7 @@ Clang-Tidy Checks
    cppcoreguidelines-special-member-functions
    fuchsia-default-arguments
    fuchsia-overloaded-operator
+   fuchsia-statically-constructed-objects
    fuchsia-virtual-inheritance
    google-build-explicit-make-pair
    google-build-namespaces

clang-tools-extra/test/clang-tidy/fuchsia-statically-constructed-objects.cpp

@@ -0,0 +1,91 @@
+// RUN: %check_clang_tidy %s fuchsia-statically-constructed-objects %t
+
+// Trivial static is fine
+static int i;
+
+class ClassWithNoCtor {};
+
+class ClassWithCtor {
+public:
+  ClassWithCtor(int Val) : Val(Val) {}
+private:
+  int Val;
+};
+
+class ClassWithConstexpr {
+public:
+  ClassWithConstexpr(int Val1, int Val2) : Val(Val1) {}
+  constexpr ClassWithConstexpr(int Val) : Val(Val) {}
+
+private:
+  int Val;
+};
+
+ClassWithNoCtor A;
+ClassWithConstexpr C(0);
+ClassWithConstexpr E(0, 1);
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  ClassWithConstexpr E(0, 1);
+ClassWithCtor G(0);
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  ClassWithCtor G(0);
+
+static ClassWithNoCtor A2;
+static ClassWithConstexpr C2(0);
+static ClassWithConstexpr E2(0, 1);
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  static ClassWithConstexpr E2(0, 1);
+static ClassWithCtor G2(0);
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  static ClassWithCtor G2(0);
+
+struct StructWithConstexpr { constexpr StructWithConstexpr(int Val) {} };
+struct StructWithNoCtor {};
+struct StructWithCtor { StructWithCtor(); };
+
+StructWithNoCtor SNoCtor;
+StructWithConstexpr SConstexpr(0);
+StructWithCtor SCtor;
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  StructWithCtor SCtor;
+
+static StructWithConstexpr SConstexpr2(0);
+static StructWithNoCtor SNoCtor2;
+static StructWithCtor SCtor2;
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  static StructWithCtor SCtor2;
+
+extern StructWithCtor SCtor3;
+
+class ClassWithStaticMember {
+private:
+  static StructWithNoCtor S;
+};
+
+ClassWithStaticMember Z();
+
+class S {
+  int Val;
+public:
+  constexpr S(int i) : Val(100 / i) {}
+  int getVal() const { return Val; }
+};
+
+static S s1(1);
+static S s2(0); 
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT: static S s2(0);
+
+extern int get_i();
+static S s3(get_i());
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: static objects are disallowed; if possible, use a constexpr constructor instead [fuchsia-statically-constructed-objects]
+// CHECK-MESSAGES-NEXT:  static S s3(get_i());
+
+void f() {
+  // Locally static is fine
+  static int i;
+  static ClassWithNoCtor A2;
+  static ClassWithConstexpr C2(0);
+  static ClassWithConstexpr E2(0, 1);
+  static ClassWithCtor G2(0);
+}