[clang-tidy] Adding Fuchsia checker for thread local storage.

[juliehockett]

Summary

Adds a check to the Fuchsia module to warn if thread-local storage is used.

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

[Eugene.Zelenko]

clang-tidy/fuchsia/ThreadLocalCheck.cpp

23

Please run Clang-format over file. This line seems to be formatted incorrectly.

docs/ReleaseNotes.rst

70

Thread storage duration seems to be proper terminology. Same for first sentence in documentation.

test/clang-tidy/fuchsia-thread-local.cpp

12

Please separate with empty line.

[juliehockett]

Fixing comments

[aaron.ballman]

clang-tidy/fuchsia/CMakeLists.txt

6

Please keep this list in alphabetical order.

clang-tidy/fuchsia/ThreadLocalCheck.cpp

27

The docs say it's only disallowed in kernel mode. Can you remind me again -- are the fuchsia checks *only* for kernel mode, or is that the "zircon" part? I'm wondering if this check is overly broad for the guidelines, basically.

[juliehockett]

After some discussion, we decided that the false positive risk for non-kernel code isn't worth the check.

clang-tidy/fuchsia/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyFuchsiaModule
   DefaultArgumentsCheck.cpp
   FuchsiaTidyModule.cpp
+  ThreadLocalCheck.cpp
   OverloadedOperatorCheck.cpp
   StaticallyConstructedObjectsCheck.cpp
   VirtualInheritanceCheck.cpp
 
   LINK_LIBS
   clangAST
   clangASTMatchers
   clangBasic
   clangLex
   clangTidy
   clangTidyUtils
   )

clang-tidy/fuchsia/FuchsiaTidyModule.cpp

 //===--- FuchsiaTidyModule.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 "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
 #include "DefaultArgumentsCheck.h"
 #include "OverloadedOperatorCheck.h"
 #include "StaticallyConstructedObjectsCheck.h"
+#include "ThreadLocalCheck.h"
 #include "VirtualInheritanceCheck.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace fuchsia {
 
 /// This module is for Fuchsia-specific checks.
 class FuchsiaModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     CheckFactories.registerCheck<DefaultArgumentsCheck>(
         "fuchsia-default-arguments");
     CheckFactories.registerCheck<OverloadedOperatorCheck>(
         "fuchsia-overloaded-operator");
     CheckFactories.registerCheck<StaticallyConstructedObjectsCheck>(
         "fuchsia-statically-constructed-objects");
+    CheckFactories.registerCheck<ThreadLocalCheck>(
+        "fuchsia-thread-local");
     CheckFactories.registerCheck<VirtualInheritanceCheck>(
         "fuchsia-virtual-inheritance");
   }
 };
 // Register the FuchsiaTidyModule using this statically initialized variable.
 static ClangTidyModuleRegistry::Add<FuchsiaModule>
     X("fuchsia-module", "Adds Fuchsia platform checks.");
 } // namespace fuchsia
 
 // This anchor is used to force the linker to link in the generated object file
 // and thus register the FuchsiaModule.
 volatile int FuchsiaModuleAnchorSource = 0;
 
 } // namespace tidy
 } // namespace clang

clang-tidy/fuchsia/ThreadLocalCheck.h

+//===--- ThreadLocalCheck.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_THREAD_LOCAL_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_THREAD_LOCAL_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+
+/// Thread storage duration is disallowed.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/fuchsia-thread-local.html
+class ThreadLocalCheck : public ClangTidyCheck {
+public:
+  ThreadLocalCheck(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_THREAD_LOCAL_H

clang-tidy/fuchsia/ThreadLocalCheck.cpp

+//===--- ThreadLocalCheck.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 "ThreadLocalCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+
+void ThreadLocalCheck::registerMatchers(MatchFinder *Finder) {
+  // Using thread storage duration is disallowed.
+  Finder->addMatcher(varDecl(hasThreadStorageDuration()).bind("decl"), this);
+}
+
+void ThreadLocalCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *D = Result.Nodes.getNodeAs<VarDecl>("decl"))
+    diag(D->getLocStart(), "thread local storage is disallowed");
+}
+
+} // namespace fuchsia
+} // namespace tidy
+} // namespace clang

docs/ReleaseNotes.rst

 
 - 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.
 
+- New `fuchsia-thread-local
+  <http://clang.llvm.org/extra/clang-tidy/checks/fuchsia-thread-local.html>`_ check
+
+  Warns if thread storage duration is used.
+
 Improvements to include-fixer
 -----------------------------
 
 The improvements are...
 
 Improvements to modularize
 --------------------------
 
 The improvements are...

docs/clang-tidy/checks/fuchsia-thread-local.rst

+.. title:: clang-tidy - fuchsia-thread-local
+
+fuchsia-thread-local
+====================
+
+Warns if thread storage duration is used.
+
+For example, using ``thread_local`` or ``extern thread_local`` is not allowed:
+
+.. code-block:: c++
+
+  thread_local int foo;           // Warning
+  extern thread_local int bar;    // Warning
+
+See the features disallowed in Fuchsia at https://fuchsia.googlesource.com/zircon/+/master/docs/cxx.md

docs/clang-tidy/checks/list.rst

.. toctree::
    cppcoreguidelines-pro-type-static-cast-downcast
    cppcoreguidelines-pro-type-union-access
    cppcoreguidelines-pro-type-vararg
    cppcoreguidelines-slicing
    cppcoreguidelines-special-member-functions
    fuchsia-default-arguments
    fuchsia-overloaded-operator
    fuchsia-statically-constructed-objects
+   fuchsia-thread-local
    fuchsia-virtual-inheritance
    google-build-explicit-make-pair
    google-build-namespaces
    google-build-using-namespace
    google-default-arguments
    google-explicit-constructor
    google-global-names-in-headers
    google-objc-avoid-throwing-exception

test/clang-tidy/fuchsia-thread-local.cpp

+// RUN: %check_clang_tidy %s fuchsia-thread-local %t
+
+int main() {
+  thread_local int foo;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: thread local storage is disallowed
+  // CHECK-NEXT:  thread_local int foo;
+
+  extern thread_local int bar;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: thread local storage is disallowed
+  // CHECK-NEXT:  extern thread_local int bar;
+  int baz;
+  
+  return 0;
+}