[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

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@322310 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 99 insertions, 0 deletions

diff --git a/clang-tidy/fuchsia/CMakeLists.txt b/clang-tidy/fuchsia/CMakeLists.txt
index 3b223ba7..28e4b0e7 100644
--- a/clang-tidy/fuchsia/CMakeLists.txt
+++ b/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
diff --git a/clang-tidy/fuchsia/FuchsiaTidyModule.cpp b/clang-tidy/fuchsia/FuchsiaTidyModule.cpp
index 1860115a..ab4aaff9 100644
--- a/clang-tidy/fuchsia/FuchsiaTidyModule.cpp
+++ b/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");
   }
diff --git a/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.cpp b/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.cpp
new file mode 100644
index 00000000..8291f988
--- /dev/null
+++ b/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
diff --git a/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.h b/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.h
new file mode 100644
index 00000000..6df9b1c2
--- /dev/null
+++ b/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