[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"
@@ -165,6 +166,8 @@ 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 +1,182 @@
+//===--- 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/AST/TypeVisitor.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <algorithm>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+bool isCompleteAndHasNoZeroValue(const EnumDecl *D) {
+  const EnumDecl *Definition = D->getDefinition();
+  return Definition && Definition->isComplete() &&
+         !Definition->enumerators().empty() &&
+         std::none_of(Definition->enumerator_begin(),
+                      Definition->enumerator_end(),
+                      [](const EnumConstantDecl *Value) {
+                        return Value->getInitVal().isZero();
+                      });
+}
+
+AST_MATCHER(EnumDecl, isCompleteAndHasNoZeroValue) {
+  return isCompleteAndHasNoZeroValue(&Node);
+}
+
+// Find an initialization which initializes the value (if it has enum type) to a
+// default zero value.
+AST_MATCHER(Expr, isEmptyInit) {
+  if (isa<CXXScalarValueInitExpr>(&Node))
+    return true;
+  if (isa<ImplicitValueInitExpr>(&Node))
+    return true;
+  if (const auto *Init = dyn_cast<InitListExpr>(&Node)) {
+    if (Init->getNumInits() == 0)
+      return true;
+  }
+  return false;
+}
+
+AST_MATCHER(InitListExpr, hasArrayFiller) { return Node.hasArrayFiller(); }
+
+// Check if any type has a "child" type that is an enum without zero value.
+// The "child" type can be an array element type or member type of a record
+// type (or a recursive combination of these). In this case, if the "root" type
+// is statically initialized, the enum component is initialized to zero.
+class FindEnumMember : public TypeVisitor<FindEnumMember, bool> {
+public:
+  const EnumType *FoundEnum = nullptr;
+
+  bool VisitType(const Type *T) {
+    const Type *DesT = T->getUnqualifiedDesugaredType();
+    if (DesT != T)
+      return Visit(DesT);
+    return false;
+  }
+  bool VisitArrayType(const ArrayType *T) {
+    return Visit(T->getElementType()->getUnqualifiedDesugaredType());
+  }
+  bool VisitConstantArrayType(const ConstantArrayType *T) {
+    return Visit(T->getElementType()->getUnqualifiedDesugaredType());
+  }
+  bool VisitEnumType(const EnumType *T) {
+    if (isCompleteAndHasNoZeroValue(T->getDecl())) {
+      FoundEnum = T;
+      return true;
+    }
+    return false;
+  }
+  bool VisitRecordType(const RecordType *T) {
+    const RecordDecl *RD = T->getDecl();
+    if (RD->isUnion())
+      return false;
+    auto VisitField = [this](const FieldDecl *F) {
+      return Visit(F->getType()->getUnqualifiedDesugaredType());
+    };
+    return llvm::any_of(RD->fields(), VisitField);
+  }
+};
+
+} // namespace
+
+InvalidEnumDefaultInitializationCheck::InvalidEnumDefaultInitializationCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {}
+
+void InvalidEnumDefaultInitializationCheck::registerMatchers(
+    MatchFinder *Finder) {
+  auto EnumWithoutZeroValue = enumType(
+      hasDeclaration(enumDecl(isCompleteAndHasNoZeroValue()).bind("enum")));
+  auto EnumOrArrayOfEnum = qualType(hasUnqualifiedDesugaredType(
+      anyOf(EnumWithoutZeroValue,
+            arrayType(hasElementType(qualType(
+                hasUnqualifiedDesugaredType(EnumWithoutZeroValue)))))));
+  Finder->addMatcher(
+      expr(isEmptyInit(), hasType(EnumOrArrayOfEnum)).bind("expr"), this);
+
+  // Array initialization can contain an "array filler" for the (syntactically)
+  // unspecified elements. This expression is not found by AST matchers and can
+  // have any type (the array's element type). This is an implicitly generated
+  // initialization, so if the type contains somewhere an enum without zero
+  // enumerator, the zero initialization applies here. We search this array
+  // element type for the specific enum type manually when this matcher matches.
+  Finder->addMatcher(initListExpr(hasArrayFiller()).bind("array_filler_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) {
+    const auto *InitList =
+        Result.Nodes.getNodeAs<InitListExpr>("array_filler_expr");
+    // Initialization of omitted array elements with array filler was found.
+    // Check the type for enum without zero value.
+    // FIXME: In this way only one enum-typed value is found, not all of these.
+    FindEnumMember Finder;
+    if (!Finder.Visit(InitList->getArrayFiller()->getType().getTypePtr()))
+      return;
+    InitExpr = InitList;
+    Enum = Finder.FoundEnum->getDecl();
+  }
+
+  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.
+    // Ideally all such cases (if they exist) should be handled to make the
+    // check 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 +1,31 @@
+//===--- 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 {
+
+/// Detects 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;
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INVALIDENUMDEFAULTINITIALIZATIONCHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -124,6 +124,12 @@ New checks
   pointer and store it as class members without handle the copy and move
   constructors and the assignments.
 
+- New :doc:`bugprone-invalid-enum-default-initialization
+  <clang-tidy/checks/bugprone/invalid-enum-default-initialization>` check.
+
+  Detects default initialization (to 0) of variables with ``enum`` type where
+  the enum has no enumerator with value of 0.
+
 - New :doc:`bugprone-misleading-setter-of-reference
   <clang-tidy/checks/bugprone/misleading-setter-of-reference>` check.
 

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

@@ -0,0 +1,72 @@
+.. title:: clang-tidy - bugprone-invalid-enum-default-initialization
+
+bugprone-invalid-enum-default-initialization
+============================================
+
+Detects 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. Unions are not
+handled by the check (if it contains a member of enum type).
+
+.. 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
+
+The check applies to initialization of arrays or structures with initialization
+lists in C code too. In these cases elements not specified in the list (and have
+enum type) are set to 0.
+
+.. code-block:: c
+
+  enum Enum1 {
+    Enum1_A = 1,
+    Enum1_B
+  };
+  struct Struct1 {
+    int a;
+    enum Enum1 b;
+  };
+
+  enum Enum1 Array1[2] = {Enum1_A}; // warn: omitted elements are initialized to 0
+  enum Enum1 Array2[2][2] = {{Enum1_A}, {Enum1_A}}; // warn: last element of both nested arrays is initialized to 0
+  enum Enum1 Array3[2][2] = {{Enum1_A, Enum1_A}}; // warn: elements of second array are initialized to 0
+
+  struct Struct1 S1 = {1}; // warn: element 'b' is initialized to 0

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -106,6 +106,7 @@ Clang-Tidy Checks
    :doc:`bugprone-incorrect-roundings <bugprone/incorrect-roundings>`,
    :doc:`bugprone-infinite-loop <bugprone/infinite-loop>`,
    :doc:`bugprone-integer-division <bugprone/integer-division>`,
+   :doc:`bugprone-invalid-enum-default-initialization <bugprone/invalid-enum-default-initialization>`,
    :doc:`bugprone-lambda-function-name <bugprone/lambda-function-name>`,
    :doc:`bugprone-macro-parentheses <bugprone/macro-parentheses>`, "Yes"
    :doc:`bugprone-macro-repeated-side-effects <bugprone/macro-repeated-side-effects>`,

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

@@ -0,0 +1,54 @@
+// RUN: %check_clang_tidy %s bugprone-invalid-enum-default-initialization %t
+
+enum Enum1 {
+  Enum1_A = 1,
+  Enum1_B
+};
+
+struct Struct1 {
+  int a;
+  enum Enum1 b;
+};
+
+struct Struct2 {
+  struct Struct1 a;
+  char b;
+};
+
+enum Enum1 E1 = {};
+// 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: :3:6: note: enum is defined here
+enum Enum1 E2[10] = {};
+// CHECK-NOTES: :[[@LINE-1]]:21: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+enum Enum1 E3[10] = {Enum1_A};
+// CHECK-NOTES: :[[@LINE-1]]:21: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+enum Enum1 E4[2][2] = {{Enum1_A}, {Enum1_A}};
+// CHECK-NOTES: :[[@LINE-1]]:24: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+// CHECK-NOTES: :[[@LINE-3]]:35: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+enum Enum1 E5[2][2] = {{Enum1_A, Enum1_A}};
+// CHECK-NOTES: :[[@LINE-1]]:23: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+
+
+struct Struct1 S1[2][2] = {{{1, Enum1_A}, {2, Enum1_A}}};
+// CHECK-NOTES: :[[@LINE-1]]:27: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+
+struct Struct2 S2[3] = {{1}};
+// CHECK-NOTES: :[[@LINE-1]]:24: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+// CHECK-NOTES: :[[@LINE-3]]:26: warning: enum value of type 'Enum1' initialized with invalid value of 0, enum doesn't have a zero-value enumerator
+// CHECK-NOTES: :3:6: note: enum is defined here
+
+union Union1 {
+  enum Enum1 a;
+  int b;
+};
+
+// no warnings for union
+union Union1 U1 = {};
+union Union1 U2[3] = {};