[clang-tidy] Add check 'bugprone-invalid-enum-default-initialization'

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

@@ -38,6 +38,7 @@
 #include "IncorrectRoundingsCheck.h"
 #include "InfiniteLoopCheck.h"
 #include "IntegerDivisionCheck.h"
+#include "InvalidEnumDefaultInitializationCheck.h"
 #include "LambdaFunctionNameCheck.h"
 #include "MacroParenthesesCheck.h"
 #include "MacroRepeatedSideEffectsCheck.h"
@@ -164,6 +165,8 @@ class BugproneModule : public ClangTidyModule {
     CheckFactories.registerCheck<InfiniteLoopCheck>("bugprone-infinite-loop");
     CheckFactories.registerCheck<IntegerDivisionCheck>(
         "bugprone-integer-division");
+    CheckFactories.registerCheck<InvalidEnumDefaultInitializationCheck>(
+        "bugprone-invalid-enum-default-initialization");
     CheckFactories.registerCheck<LambdaFunctionNameCheck>(
         "bugprone-lambda-function-name");
     CheckFactories.registerCheck<MacroParenthesesCheck>(

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

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

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

@@ -0,0 +1,112 @@
+//===--- InvalidEnumDefaultInitializationCheck.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 "InvalidEnumDefaultInitializationCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <algorithm>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+AST_MATCHER(EnumDecl, isCompleteAndHasNoZeroValue) {
+  const EnumDecl *Definition = Node.getDefinition();
+  return Definition && Node.isComplete() && !Node.enumerators().empty() &&
+         std::none_of(Definition->enumerator_begin(),
+                      Definition->enumerator_end(),
+                      [](const EnumConstantDecl *Value) {
+                        return Value->getInitVal().isZero();
+                      });
+}
+
+AST_MATCHER(Expr, isEmptyInit) {
+  if (isa<CXXScalarValueInitExpr>(&Node))
+    return true;
+  if (isa<ImplicitValueInitExpr>(&Node))
+    return true;
+  if (const auto *Init = dyn_cast<InitListExpr>(&Node))
+    return Init->getNumInits() == 0;
+  return false;
+}
+
+} // namespace
+
+InvalidEnumDefaultInitializationCheck::InvalidEnumDefaultInitializationCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {}
+
+bool InvalidEnumDefaultInitializationCheck::isLanguageVersionSupported(
+    const LangOptions &LangOpts) const {
+  return LangOpts.CPlusPlus;
+}
+
+void InvalidEnumDefaultInitializationCheck::registerMatchers(
+    MatchFinder *Finder) {
+  Finder->addMatcher(
+      expr(isEmptyInit(),
+           hasType(hasUnqualifiedDesugaredType(enumType(hasDeclaration(
+               enumDecl(isCompleteAndHasNoZeroValue()).bind("enum"))))))
+          .bind("expr"),
+      this);
+}
+
+void InvalidEnumDefaultInitializationCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *InitExpr = Result.Nodes.getNodeAs<Expr>("expr");
+  const auto *Enum = Result.Nodes.getNodeAs<EnumDecl>("enum");
+  if (!InitExpr || !Enum)
+    return;
+
+  ASTContext &ACtx = Enum->getASTContext();
+  SourceLocation Loc = InitExpr->getExprLoc();
+  if (Loc.isInvalid()) {
+    if (isa<ImplicitValueInitExpr>(InitExpr) || isa<InitListExpr>(InitExpr)) {
+      DynTypedNodeList Parents = ACtx.getParents(*InitExpr);
+      if (Parents.empty())
+        return;
+
+      if (const auto *Ctor = Parents[0].get<CXXConstructorDecl>()) {
+        // Try to find member initializer with the found expression and get the
+        // source location from it.
+        CXXCtorInitializer *const *CtorInit = std::find_if(
+            Ctor->init_begin(), Ctor->init_end(),
+            [InitExpr](const CXXCtorInitializer *Init) {
+              return Init->isMemberInitializer() && Init->getInit() == InitExpr;
+            });
+        if (!CtorInit)
+          return;
+        Loc = (*CtorInit)->getLParenLoc();
+      } else if (const auto *InitList = Parents[0].get<InitListExpr>()) {
+        // The expression may be implicitly generated for an initialization.
+        // Search for a parent initialization list with valid source location.
+        while (InitList->getExprLoc().isInvalid()) {
+          DynTypedNodeList Parents = ACtx.getParents(*InitList);
+          if (Parents.empty())
+            return;
+          InitList = Parents[0].get<InitListExpr>();
+          if (!InitList)
+            return;
+        }
+        Loc = InitList->getExprLoc();
+      }
+    }
+    // If still not found a source location, omit the warning.
+    // FIXME: All such cases should be fixed to make the checker more precise.
+    if (Loc.isInvalid())
+      return;
+  }
+  diag(Loc, "enum value of type %0 initialized with invalid value of 0, "
+            "enum doesn't have a zero-value enumerator")
+      << Enum;
+  diag(Enum->getLocation(), "enum is defined here", DiagnosticIDs::Note);
+}
+
+} // namespace clang::tidy::bugprone

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

@@ -0,0 +1,32 @@
+//===--- InvalidEnumDefaultInitializationCheck.h - clang-tidy -*- C++ -*---===//
+//
+// 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_INVALIDENUMDEFAULTINITIALIZATIONCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INVALIDENUMDEFAULTINITIALIZATIONCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::bugprone {
+
+/// Detect default initialization (to 0) of variables with `enum` type where
+/// the enum has no enumerator with value of 0.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone/invalid-enum-default-initialization.html
+class InvalidEnumDefaultInitializationCheck : public ClangTidyCheck {
+public:
+  InvalidEnumDefaultInitializationCheck(StringRef Name,
+                                        ClangTidyContext *Context);
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override;
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INVALIDENUMDEFAULTINITIALIZATIONCHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -125,6 +125,12 @@ New checks
   Finds potentially erroneous calls to ``reset`` method on smart pointers when
   the pointee type also has a ``reset`` method.
 
+- New :doc:`bugprone-invalid-enum-default-initialization
+  <clang-tidy/checks/bugprone/invalid-enum-default-initialization>` check.
+
+  Detect default initialization (to 0) of variables with ``enum`` type where
+  the enum has no enumerator with value of 0.
+
 New check aliases
 ^^^^^^^^^^^^^^^^^
 

clang-tools-extra/docs/clang-tidy/checks/bugprone/invalid-enum-default-initialization.rst

@@ -0,0 +1,50 @@
+.. title:: clang-tidy - bugprone-invalid-enum-default-initialization
+
+bugprone-invalid-enum-default-initialization
+============================================
+
+Detect default initialization (to 0) of variables with ``enum`` type where
+the enum has no enumerator with value of 0.
+
+In C++ a default initialization is performed if a variable is initialized with
+initializer list or in other implicit ways, and no value is specified at the
+initialization. In such cases the value 0 is used for the initialization.
+This also applies to enumerations even if it does not have an enumerator with
+value 0. In this way a variable with the enum type may contain initially an
+invalid value (if the program expects that it contains only the listed
+enumerator values).
+
+The checker emits a warning only if an enum variable is default-initialized
+(contrary to not initialized) and the enum type does not have an enumerator with
+value of 0. The enum type can be scoped or non-scoped enum.
+
+.. code-block:: c++
+
+  enum class Enum1: int {
+    A = 1,
+    B
+  };
+
+  enum class Enum0: int {
+    A = 0,
+    B
+  };
+
+  void f() {
+    Enum1 X1{}; // warn: 'X1' is initialized to 0
+    Enum1 X2 = Enum1(); // warn: 'X2' is initialized to 0
+    Enum1 X3; // no warning: 'X3' is not initialized
+    Enum0 X4{}; // no warning: type has an enumerator with value of 0
+  }
+
+  struct S1 {
+    Enum1 A;
+    S(): A() {} // warn: 'A' is initialized to 0
+  };
+
+  struct S2 {
+    int A;
+    Enum1 B;
+  };
+
+  S2 VarS2{}; // warn: member 'B' is initialized to 0

clang-tools-extra/test/clang-tidy/checkers/bugprone/invalid-enum-default-initialization.cpp

@@ -0,0 +1,133 @@
+// RUN: %check_clang_tidy -std=c++17 %s bugprone-invalid-enum-default-initialization %t
+
+enum class Enum0: int {
+  A = 0,
+  B
+};
+
+enum class Enum1: int {
+  A = 1,
+  B
+};
+
+enum Enum2 {
+  Enum_A = 4,
+  Enum_B
+};
+
+Enum0 E0_1{};
+Enum0 E0_2 = Enum0();
+Enum0 E0_3;
+Enum0 E0_4{0};
+Enum0 E0_5{Enum0::A};
+Enum0 E0_6{Enum0::B};
+
+Enum1 E1_1{};
+// CHECK-NOTES: :[[@LINE-1]]:11: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :8:12: note: enum is defined here
+Enum1 E1_2 = Enum1();
+// CHECK-NOTES: :[[@LINE-1]]:14: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :8:12: note: enum is defined here
+Enum1 E1_3;
+Enum1 E1_4{0};
+Enum1 E1_5{Enum1::A};
+Enum1 E1_6{Enum1::B};
+
+Enum2 E2_1{};
+// CHECK-NOTES: :[[@LINE-1]]:11: warning: enum value of type 'Enum2' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :13:6: note: enum is defined here
+Enum2 E2_2 = Enum2();
+// CHECK-NOTES: :[[@LINE-1]]:14: warning: enum value of type 'Enum2' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :13:6: note: enum is defined here
+
+void f1() {
+  static Enum1 S; // FIMXE: warn for this?
+  Enum1 A;
+  Enum1 B = Enum1();
+  // CHECK-NOTES: :[[@LINE-1]]:13: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+  // CHECK-NOTES: :8:12: note: enum is defined here
+  int C = int();
+}
+
+void f2() {
+  Enum1 A{};
+  // CHECK-NOTES: :[[@LINE-1]]:10: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+  // CHECK-NOTES: :8:12: note: enum is defined here
+  Enum1 B = Enum1();
+  // CHECK-NOTES: :[[@LINE-1]]:13: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+  // CHECK-NOTES: :8:12: note: enum is defined here
+  Enum1 C[5] = {{}};
+  // CHECK-NOTES: :[[@LINE-1]]:17: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+  // CHECK-NOTES: :8:12: note: enum is defined here
+  Enum1 D[5] = {}; // FIMXE: warn for this?
+}
+
+struct S1 {
+  Enum1 E_1{};
+  // CHECK-NOTES: :[[@LINE-1]]:12: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+  // CHECK-NOTES: :8:12: note: enum is defined here
+  Enum1 E_2 = Enum1();
+  // CHECK-NOTES: :[[@LINE-1]]:15: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+  // CHECK-NOTES: :8:12: note: enum is defined here
+  Enum1 E_3;
+  Enum1 E_4;
+  Enum1 E_5;
+
+  S1() :
+    E_3{},
+    // CHECK-NOTES: :[[@LINE-1]]:8: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+    // CHECK-NOTES: :8:12: note: enum is defined here
+    E_4(),
+    // CHECK-NOTES: :[[@LINE-1]]:8: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+    // CHECK-NOTES: :8:12: note: enum is defined here
+    E_5{Enum1::B}
+  {}
+};
+
+struct S2 {
+  Enum0 X;
+  Enum1 Y;
+  Enum2 Z;
+};
+
+struct S3 {
+  S2 X;
+  int Y;
+};
+
+struct S4 : public S3 {
+  int Z;
+};
+
+S2 VarS2{};
+// CHECK-NOTES: :[[@LINE-1]]:9: warning: enum value of type 'Enum1' initialized with invalid value of 0
+// CHECK-NOTES: :8:12: note: enum is defined here
+// CHECK-NOTES: :[[@LINE-3]]:9: warning: enum value of type 'Enum2' initialized with invalid value of 0
+// CHECK-NOTES: :13:6: note: enum is defined here
+S3 VarS3{};
+// CHECK-NOTES: :[[@LINE-1]]:10: warning: enum value of type 'Enum1' initialized with invalid value of 0
+// CHECK-NOTES: :8:12: note: enum is defined here
+// CHECK-NOTES: :[[@LINE-3]]:10: warning: enum value of type 'Enum2' initialized with invalid value of 0
+// CHECK-NOTES: :13:6: note: enum is defined here
+S4 VarS4{};
+// CHECK-NOTES: :[[@LINE-1]]:10: warning: enum value of type 'Enum1' initialized with invalid value of 0
+// CHECK-NOTES: :8:12: note: enum is defined here
+// CHECK-NOTES: :[[@LINE-3]]:10: warning: enum value of type 'Enum2' initialized with invalid value of 0
+// CHECK-NOTES: :13:6: note: enum is defined here
+
+enum class EnumFwd;
+
+EnumFwd Fwd{};
+
+enum class EnumEmpty {};
+
+EnumEmpty Empty{};
+
+template<typename T>
+struct Templ {
+  T Mem1{};
+  // CHECK-NOTES: :[[@LINE-1]]:9: warning: enum value of type 'Enum1' initialized with invalid value of 0
+  // CHECK-NOTES: :8:12: note: enum is defined here
+};
+
+Templ<Enum1> TemplVar;