[clang-tidy] support pointee mutation check in misc-const-correctness

clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp

@@ -13,6 +13,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
+#include <cassert>
 
 using namespace clang::ast_matchers;
 
@@ -37,36 +38,54 @@ AST_MATCHER(Type, isDependentType) { return Node.isDependentType(); }
 ConstCorrectnessCheck::ConstCorrectnessCheck(StringRef Name,
                                              ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
-      AnalyzeValues(Options.get("AnalyzeValues", true)),
+      AnalyzePointers(Options.get("AnalyzePointers", true)),
       AnalyzeReferences(Options.get("AnalyzeReferences", true)),
+      AnalyzeValues(Options.get("AnalyzeValues", true)),
+
+      WarnPointersAsPointers(Options.get("WarnPointersAsPointers", true)),
       WarnPointersAsValues(Options.get("WarnPointersAsValues", false)),
-      TransformValues(Options.get("TransformValues", true)),
-      TransformReferences(Options.get("TransformReferences", true)),
+
+      TransformPointersAsPointers(
+          Options.get("TransformPointersAsPointers", true)),
       TransformPointersAsValues(
           Options.get("TransformPointersAsValues", false)),
+      TransformReferences(Options.get("TransformReferences", true)),
+      TransformValues(Options.get("TransformValues", true)),
+
       AllowedTypes(
           utils::options::parseStringList(Options.get("AllowedTypes", ""))) {
-  if (AnalyzeValues == false && AnalyzeReferences == false)
+  if (AnalyzeValues == false && AnalyzeReferences == false &&
+      AnalyzePointers == false)
     this->configurationDiag(
         "The check 'misc-const-correctness' will not "
-        "perform any analysis because both 'AnalyzeValues' and "
-        "'AnalyzeReferences' are false.");
+        "perform any analysis because 'AnalyzeValues', "
+        "'AnalyzeReferences' and 'AnalyzePointers' are false.");
 }
 
 void ConstCorrectnessCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
-  Options.store(Opts, "AnalyzeValues", AnalyzeValues);
+  Options.store(Opts, "AnalyzePointers", AnalyzePointers);
   Options.store(Opts, "AnalyzeReferences", AnalyzeReferences);
+  Options.store(Opts, "AnalyzeValues", AnalyzeValues);
+
+  Options.store(Opts, "WarnPointersAsPointers", WarnPointersAsPointers);
   Options.store(Opts, "WarnPointersAsValues", WarnPointersAsValues);
 
-  Options.store(Opts, "TransformValues", TransformValues);
-  Options.store(Opts, "TransformReferences", TransformReferences);
+  Options.store(Opts, "TransformPointersAsPointers",
+                TransformPointersAsPointers);
   Options.store(Opts, "TransformPointersAsValues", TransformPointersAsValues);
+  Options.store(Opts, "TransformReferences", TransformReferences);
+  Options.store(Opts, "TransformValues", TransformValues);
+
   Options.store(Opts, "AllowedTypes",
                 utils::options::serializeStringList(AllowedTypes));
 }
 
 void ConstCorrectnessCheck::registerMatchers(MatchFinder *Finder) {
-  const auto ConstType = hasType(isConstQualified());
+  const auto ConstType = hasType(
+      qualType(isConstQualified(),
+               // pointee check will check the const pointer and const array
+               unless(pointerType()), unless(arrayType())));
+
   const auto ConstReference = hasType(references(isConstQualified()));
   const auto RValueReference = hasType(
       referenceType(anyOf(rValueReferenceType(), unless(isSpelledAsLValue()))));
@@ -124,6 +143,11 @@ void ConstCorrectnessCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *LocalScope = Result.Nodes.getNodeAs<Stmt>("scope");
   const auto *Variable = Result.Nodes.getNodeAs<VarDecl>("local-value");
   const auto *Function = Result.Nodes.getNodeAs<FunctionDecl>("function-decl");
+  const auto *VarDeclStmt = Result.Nodes.getNodeAs<DeclStmt>("decl-stmt");
+  // It can not be guaranteed that the variable is declared isolated,
+  // therefore a transformation might effect the other variables as well and
+  // be incorrect.
+  const bool CanBeFixIt = VarDeclStmt != nullptr && VarDeclStmt->isSingleDecl();
 
   /// If the variable was declared in a template it might be analyzed multiple
   /// times. Only one of those instantiations shall emit a warning. NOTE: This
@@ -137,72 +161,102 @@ void ConstCorrectnessCheck::check(const MatchFinder::MatchResult &Result) {
 
   VariableCategory VC = VariableCategory::Value;
   const QualType VT = Variable->getType();
-  if (VT->isReferenceType())
+  if (VT->isReferenceType()) {
     VC = VariableCategory::Reference;
-  else if (VT->isPointerType())
+  } else if (VT->isPointerType()) {
     VC = VariableCategory::Pointer;
-  else if (const auto *ArrayT = dyn_cast<ArrayType>(VT))
+  } else if (const auto *ArrayT = dyn_cast<ArrayType>(VT)) {
     if (ArrayT->getElementType()->isPointerType())
       VC = VariableCategory::Pointer;
+  }
 
-  // Each variable can only be in one category: Value, Pointer, Reference.
-  // Analysis can be controlled for every category.
-  if (VC == VariableCategory::Reference && !AnalyzeReferences)
-    return;
-
-  if (VC == VariableCategory::Reference &&
-      Variable->getType()->getPointeeType()->isPointerType() &&
-      !WarnPointersAsValues)
-    return;
-
-  if (VC == VariableCategory::Pointer && !WarnPointersAsValues)
-    return;
-
-  if (VC == VariableCategory::Value && !AnalyzeValues)
-    return;
-
-  // The scope is only registered if the analysis shall be run.
-  registerScope(LocalScope, Result.Context);
-
-  // Offload const-analysis to utility function.
-  if (ScopesCache[LocalScope]->isMutated(Variable))
-    return;
-
-  auto Diag = diag(Variable->getBeginLoc(),
-                   "variable %0 of type %1 can be declared 'const'")
-              << Variable << Variable->getType();
-  if (IsNormalVariableInTemplate)
-    TemplateDiagnosticsCache.insert(Variable->getBeginLoc());
+  auto CheckValue = [&]() {
+    // The scope is only registered if the analysis shall be run.
+    registerScope(LocalScope, Result.Context);
+
+    // Offload const-analysis to utility function.
+    if (ScopesCache[LocalScope]->isMutated(Variable))
+      return;
+
+    auto Diag = diag(Variable->getBeginLoc(),
+                     "variable %0 of type %1 can be declared 'const'")
+                << Variable << VT;
+    if (IsNormalVariableInTemplate)
+      TemplateDiagnosticsCache.insert(Variable->getBeginLoc());
+    if (!CanBeFixIt)
+      return;
+    using namespace utils::fixit;
+    if (VC == VariableCategory::Value && TransformValues) {
+      Diag << addQualifierToVarDecl(*Variable, *Result.Context,
+                                    Qualifiers::Const, QualifierTarget::Value,
+                                    QualifierPolicy::Right);
+      // FIXME: Add '{}' for default initialization if no user-defined default
+      // constructor exists and there is no initializer.
+      return;
+    }
 
-  const auto *VarDeclStmt = Result.Nodes.getNodeAs<DeclStmt>("decl-stmt");
+    if (VC == VariableCategory::Reference && TransformReferences) {
+      Diag << addQualifierToVarDecl(*Variable, *Result.Context,
+                                    Qualifiers::Const, QualifierTarget::Value,
+                                    QualifierPolicy::Right);
+      return;
+    }
 
-  // It can not be guaranteed that the variable is declared isolated, therefore
-  // a transformation might effect the other variables as well and be incorrect.
-  if (VarDeclStmt == nullptr || !VarDeclStmt->isSingleDecl())
-    return;
+    if (VC == VariableCategory::Pointer && TransformPointersAsValues) {
+      Diag << addQualifierToVarDecl(*Variable, *Result.Context,
+                                    Qualifiers::Const, QualifierTarget::Value,
+                                    QualifierPolicy::Right);
+      return;
+    }
+  };
+
+  auto CheckPointee = [&]() {
+    assert(VC == VariableCategory::Pointer);
+    registerScope(LocalScope, Result.Context);
+    if (ScopesCache[LocalScope]->isPointeeMutated(Variable))
+      return;
+    auto Diag =
+        diag(Variable->getBeginLoc(),
+             "pointee of variable %0 of type %1 can be declared 'const'")
+        << Variable << VT;
+    if (IsNormalVariableInTemplate)
+      TemplateDiagnosticsCache.insert(Variable->getBeginLoc());
+    if (!CanBeFixIt)
+      return;
+    using namespace utils::fixit;
+    if (TransformPointersAsPointers) {
+      Diag << addQualifierToVarDecl(*Variable, *Result.Context,
+                                    Qualifiers::Const, QualifierTarget::Pointee,
+                                    QualifierPolicy::Right);
+    }
+  };
 
-  using namespace utils::fixit;
-  if (VC == VariableCategory::Value && TransformValues) {
-    Diag << addQualifierToVarDecl(*Variable, *Result.Context, Qualifiers::Const,
-                                  QualifierTarget::Value,
-                                  QualifierPolicy::Right);
-    // FIXME: Add '{}' for default initialization if no user-defined default
-    // constructor exists and there is no initializer.
+  // Each variable can only be in one category: Value, Pointer, Reference.
+  // Analysis can be controlled for every category.
+  if (VC == VariableCategory::Value && AnalyzeValues) {
+    CheckValue();
     return;
   }
-
-  if (VC == VariableCategory::Reference && TransformReferences) {
-    Diag << addQualifierToVarDecl(*Variable, *Result.Context, Qualifiers::Const,
-                                  QualifierTarget::Value,
-                                  QualifierPolicy::Right);
+  if (VC == VariableCategory::Reference && AnalyzeReferences) {
+    if (VT->getPointeeType()->isPointerType() && !WarnPointersAsValues)
+      return;
+    CheckValue();
     return;
   }
-
-  if (VC == VariableCategory::Pointer) {
-    if (WarnPointersAsValues && TransformPointersAsValues) {
-      Diag << addQualifierToVarDecl(*Variable, *Result.Context,
-                                    Qualifiers::Const, QualifierTarget::Value,
-                                    QualifierPolicy::Right);
+  if (VC == VariableCategory::Pointer && AnalyzePointers) {
+    if (WarnPointersAsValues && !VT.isConstQualified())
+      CheckValue();
+    if (WarnPointersAsPointers) {
+      if (const auto *PT = dyn_cast<PointerType>(VT)) {
+        if (!PT->getPointeeType().isConstQualified())
+          CheckPointee();
+      }
+      if (const auto *AT = dyn_cast<ArrayType>(VT)) {
+        if (!AT->getElementType().isConstQualified()) {
+          assert(AT->getElementType()->isPointerType());
+          CheckPointee();
+        }
+      }
     }
     return;
   }

clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.h

@@ -38,13 +38,18 @@ class ConstCorrectnessCheck : public ClangTidyCheck {
   llvm::DenseMap<const Stmt *, MutationAnalyzer> ScopesCache;
   llvm::DenseSet<SourceLocation> TemplateDiagnosticsCache;
 
-  const bool AnalyzeValues;
+  const bool AnalyzePointers;
   const bool AnalyzeReferences;
+  const bool AnalyzeValues;
+
+  const bool WarnPointersAsPointers;
   const bool WarnPointersAsValues;
 
-  const bool TransformValues;
-  const bool TransformReferences;
+  const bool TransformPointersAsPointers;
   const bool TransformPointersAsValues;
+  const bool TransformReferences;
+  const bool TransformValues;
+
   const std::vector<StringRef> AllowedTypes;
 };
 

clang-tools-extra/docs/ReleaseNotes.rst

@@ -132,7 +132,8 @@ Changes in existing checks
   <clang-tidy/checks/misc/const-correctness>` check by adding the option
   `AllowedTypes`, that excludes specified types from const-correctness
   checking and fixing false positives when modifying variant by ``operator[]``
-  with template in parameters.
+  with template in parameters and supporting to check pointee mutation by
+  `AnalyzePointers` option.
 
 - Improved :doc:`misc-redundant-expression
   <clang-tidy/checks/misc/redundant-expression>` check by providing additional

clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst

@@ -21,7 +21,7 @@ as potential ``const``.
   int result = i * i;       // Before transformation
   int const result = i * i; // After transformation
 
-The check can analyze values, pointers and references but not (yet) pointees:
+The check can analyze values, pointers and references and pointees:
 
 .. code-block:: c++
 
@@ -39,8 +39,9 @@ The check can analyze values, pointers and references but not (yet) pointees:
   int const& reference_value = potential_const_int; // After transformation
   int another_copy = reference_value;
 
-  // The similar semantics of pointers are not (yet) analyzed.
-  int *pointer_variable = &potential_const_int; // _NO_ 'const int *pointer_variable' suggestion.
+  // The similar semantics of pointers are analyzed.
+  int *pointer_variable = &potential_const_int; // Before transformation
+  int const*const pointer_variable = &potential_const_int; // After transformation, both pointer itself and pointee are supported.
   int last_copy = *pointer_variable;
 
 The automatic code transformation is only applied to variables that are declared in single
@@ -61,22 +62,6 @@ Different instantiations can result in different ``const`` correctness propertie
 is not possible to find all instantiations of a template. The template might be used differently in
 an independent translation unit.
 
-Pointees can not be analyzed for constness yet. The following code shows this limitation.
-
-.. code-block:: c++
-
-  // Declare a variable that will not be modified.
-  int constant_value = 42;
-
-  // Declare a pointer to that variable, that does not modify either, but misses 'const'.
-  // Could be 'const int *pointer_to_constant = &constant_value;'
-  int *pointer_to_constant = &constant_value;
-
-  // Usage:
-  int result = 520 * 120 * (*pointer_to_constant);
-
-This limitation affects the capability to add ``const`` to methods which is not possible, too.
-
 Options
 -------
 
@@ -110,6 +95,13 @@ Options
     // No warning
     int const& ref = i;
 
+.. option:: AnalyzePointers
+
+  Enable or disable the analysis of pointers variables, like
+  ``int *ptr = &i;``. For specific checks, see 
+  :option:`WarnPointersAsValues` and :option:`WarnPointersAsPointers`.
+  Default is `true`.
+
 .. option:: WarnPointersAsValues
 
   This option enables the suggestion for ``const`` of the pointer itself.
@@ -125,6 +117,22 @@ Options
     // No warning
     const int *const pointer_variable = &value;
 
+.. option:: WarnPointersAsPointers
+
+  This option enables the suggestion for ``const`` of the value pointing to.
+  Default is `true`.
+
+  Requires :option:`AnalyzePointers` to be `true`.
+
+  .. code-block:: c++
+
+    int value = 42;
+
+    // No warning
+    const int *const pointer_variable = &value;
+    // Warning
+    int *const pointer_variable = &value;
+
 .. option:: TransformValues
 
   Provides fixit-hints for value types that automatically add ``const`` if
@@ -200,6 +208,27 @@ Options
     int *changing_pointee = &value;
     changing_pointee = &result;
 
+.. option:: TransformPointersAsPointers
+
+  Provides fix-it hints for pointers if the value it pointing to is not changed.
+  Default is `false`.
+
+  Requires :option:`WarnPointersAsPointers` to be `true`.
+
+  .. code-block:: c++
+
+    int value = 42;
+
+    // Before
+    int * pointer_variable = &value;
+    // After
+    const int * pointer_variable = &value;
+
+    // Before
+    int * a[] = {&value, &value};
+    // After
+    const int * a[] = {&value, &value};
+
 .. option:: AllowedTypes
 
   A semicolon-separated list of names of types that will be excluded from

clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-allowed-types.cpp

@@ -3,7 +3,8 @@
 // RUN:     misc-const-correctness.AllowedTypes: '[Pp]ointer$;[Pp]tr$;[Rr]ef(erence)?$;qualified::Type;::fully::QualifiedType;ConstTemplate', \
 // RUN:     misc-const-correctness.TransformPointersAsValues: true, \
 // RUN:     misc-const-correctness.TransformReferences: true, \
-// RUN:     misc-const-correctness.WarnPointersAsValues: true } \
+// RUN:     misc-const-correctness.WarnPointersAsValues: true, \
+// RUN:     misc-const-correctness.WarnPointersAsPointers: false } \
 // RUN:   }" -- -fno-delayed-template-parsing
 
 struct SmartPointer {