Add bugprone-uninitialized-thread-local to detect when thread-locals might be accessed without initialization

clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp

@@ -91,6 +91,7 @@
 #include "UndelegatedConstructorCheck.h"
 #include "UnhandledExceptionAtNewCheck.h"
 #include "UnhandledSelfAssignmentCheck.h"
+#include "UninitializedThreadLocalCheck.h"
 #include "UnintendedCharOstreamOutputCheck.h"
 #include "UniquePtrArrayMismatchCheck.h"
 #include "UnsafeFunctionsCheck.h"

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

@@ -30,6 +30,7 @@ add_clang_library(clangTidyBugproneModule STATIC
   InaccurateEraseCheck.cpp
   IncorrectEnableIfCheck.cpp
   IncorrectEnableSharedFromThisCheck.cpp
+  UninitializedThreadLocalCheck.cpp
   UnintendedCharOstreamOutputCheck.cpp
   ReturnConstRefFromParameterCheck.cpp
   SuspiciousStringviewDataUsageCheck.cpp

clang-tools-extra/clang-tidy/bugprone/UninitializedThreadLocalCheck.cpp

@@ -0,0 +1,46 @@
+//===--- UninitializedThreadLocalCheck.cpp - clang-tidy
+//--------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UninitializedThreadLocalCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+UninitializedThreadLocalCheck::UninitializedThreadLocalCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {}
+
+void UninitializedThreadLocalCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      declRefExpr(
+          // Fast check -- bail out quickly before slower filters
+          to(varDecl(hasThreadStorageDuration(),
+                     hasDeclContext(functionDecl()))),
+          forCallable(decl().bind("ctx")),
+          to(varDecl(unless(hasDeclContext(equalsBoundNode("ctx"))))))
+          .bind("declref"),
+      this);
+}
+
+void UninitializedThreadLocalCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *E = Result.Nodes.getNodeAs<DeclRefExpr>("declref");
+  diag(E->getLocation(),
+       "variable '%0' might not have been initialized on the current thread. "
+       "To guarantee prior initialization on the same thread that performs the "
+       "access, consider capturing the address of the variable in the same "
+       "block as its initialization, then use the captured address to the "
+       "desired code.")
+      << E;
+}
+
+} // namespace clang::tidy::bugprone

clang-tools-extra/clang-tidy/bugprone/UninitializedThreadLocalCheck.h

@@ -0,0 +1,33 @@
+//===--- UninitializedThreadLocalCheck.cpp - Clang tidy tool --------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNINITIALIZEDTHREADLOCALCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNINITIALIZEDTHREADLOCALCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::runtime {
+
+// Finds accesses to thread_local variables that might occur prior to
+// initialization.
+class UninitializedThreadLocalCheck : public ClangTidyCheck {
+public:
+  UninitializedThreadLocalCheck(StringRef Name, ClangTidyContext *Context);
+
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus;
+  }
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+};
+
+} // namespace clang::tidy::runtime
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNINITIALIZEDTHREADLOCALCHECK_H

clang-tools-extra/test/clang-tidy/checkers/bugprone/uninitialized-thread-local.cpp

@@ -0,0 +1,16 @@
+// RUN: %check_clang_tidy %s bugprone-uninitialized-thread-local %t
+
+thread_local int global_tls = 1;
+
+int main() {
+  thread_local int local_tls = 2;
+  {
+    ++global_tls; // no warning
+    ++local_tls; // no warning
+  }
+  auto f = []() {
+    return local_tls + global_tls;
+    // CHECK-MESSAGES: [[@LINE-1]]:12: warning: variable 'local_tls' might not have been initialized on the current thread.
+  };
+  return f();
+}