PiotrZSL created this revision.
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Detects implicit conversions between pointers of different levels of
indirection.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D149084
Files:
clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.cpp
clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.h
clang-tools-extra/docs/ReleaseNotes.rst
clang-tools-extra/docs/clang-tidy/checks/bugprone/multi-level-implicit-pointer-conversion.rst
clang-tools-extra/docs/clang-tidy/checks/list.rst
clang-tools-extra/test/clang-tidy/checkers/bugprone/multi-level-implicit-pointer-conversion.cpp
Index: clang-tools-extra/test/clang-tidy/checkers/bugprone/multi-level-implicit-pointer-conversion.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/test/clang-tidy/checkers/bugprone/multi-level-implicit-pointer-conversion.cpp
@@ -0,0 +1,65 @@
+// RUN: %check_clang_tidy %s bugprone-multi-level-implicit-pointer-conversion %t
+
+using OneStar = void*;
+using OneStarFancy = OneStar;
+
+void takeFirstLevelVoidPtr(OneStar message);
+void takeFirstLevelConstVoidPtr(const OneStarFancy message);
+void takeFirstLevelConstVoidPtrConst(const void* const message);
+void takeSecondLevelVoidPtr(void** message);
+
+void** getSecondLevelVoidPtr();
+void* getFirstLevelVoidPtr();
+int** getSecondLevelIntPtr();
+int* getFirstLevelIntPtr();
+
+int table[5];
+
+void test()
+{
+ void** secondLevelVoidPtr;
+ int* firstLevelIntPtr;
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:13: warning: multilevel pointer conversion from 'void **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ void* a = getSecondLevelVoidPtr();
+
+ void** b = getSecondLevelVoidPtr();
+ void* c = getFirstLevelVoidPtr();
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:13: warning: multilevel pointer conversion from 'int **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ void* d = getSecondLevelIntPtr();
+
+ takeFirstLevelVoidPtr(&table);
+
+ takeFirstLevelVoidPtr(firstLevelIntPtr);
+
+ takeFirstLevelVoidPtr(getFirstLevelIntPtr());
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:25: warning: multilevel pointer conversion from 'void **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelVoidPtr(secondLevelVoidPtr);
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:30: warning: multilevel pointer conversion from 'void **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelConstVoidPtr(secondLevelVoidPtr);
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:35: warning: multilevel pointer conversion from 'void **' to 'const void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelConstVoidPtrConst(secondLevelVoidPtr);
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:35: warning: multilevel pointer conversion from 'void ***' to 'const void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelConstVoidPtrConst(&secondLevelVoidPtr);
+
+ takeSecondLevelVoidPtr(secondLevelVoidPtr);
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:25: warning: multilevel pointer conversion from 'void **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelVoidPtr(getSecondLevelVoidPtr());
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:30: warning: multilevel pointer conversion from 'void **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelConstVoidPtr(getSecondLevelVoidPtr());
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:35: warning: multilevel pointer conversion from 'void **' to 'const void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelConstVoidPtrConst(getSecondLevelVoidPtr());
+
+ // CHECK-MESSAGES: :[[@LINE+1]]:25: warning: multilevel pointer conversion from 'int **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]
+ takeFirstLevelVoidPtr(getSecondLevelIntPtr());
+
+ takeSecondLevelVoidPtr(getSecondLevelVoidPtr());
+}
Index: clang-tools-extra/docs/clang-tidy/checks/list.rst
===================================================================
--- clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -102,6 +102,7 @@
`bugprone-misplaced-pointer-arithmetic-in-alloc <bugprone/misplaced-pointer-arithmetic-in-alloc.html>`_, "Yes"
`bugprone-misplaced-widening-cast <bugprone/misplaced-widening-cast.html>`_,
`bugprone-move-forwarding-reference <bugprone/move-forwarding-reference.html>`_, "Yes"
+ `bugprone-multi-level-implicit-pointer-conversion <bugprone/multi-level-implicit-pointer-conversion.html>`_,
`bugprone-multiple-statement-macro <bugprone/multiple-statement-macro.html>`_,
`bugprone-no-escape <bugprone/no-escape.html>`_,
`bugprone-non-zero-enum-to-bool-conversion <bugprone/non-zero-enum-to-bool-conversion.html>`_,
Index: clang-tools-extra/docs/clang-tidy/checks/bugprone/multi-level-implicit-pointer-conversion.rst
===================================================================
--- /dev/null
+++ clang-tools-extra/docs/clang-tidy/checks/bugprone/multi-level-implicit-pointer-conversion.rst
@@ -0,0 +1,45 @@
+.. title:: clang-tidy - bugprone-multi-level-implicit-pointer-conversion
+
+bugprone-multi-level-implicit-pointer-conversion
+================================================
+
+Detects implicit conversions between pointers of different levels of
+indirection.
+
+Conversions between pointer types of different levels of indirection can be
+dangerous and may lead to undefined behavior, particularly if the converted
+pointer is later cast to a type with a different level of indirection.
+For example, converting a pointer to a pointer to an ``int`` (``int**``) to
+a ``void*`` can result in the loss of information about the original level of
+indirection, which can cause problems when attempting to use the converted
+pointer. If the converted pointer is later cast to a type with a different
+level of indirection and dereferenced, it may lead to access violations,
+memory corruption, or other undefined behavior.
+
+Consider the following example:
+
+.. code-block:: c++
+
+ void foo(void* ptr);
+
+ int main() {
+ int x = 42;
+ int* ptr = &x;
+ int** ptr_ptr = &ptr;
+ foo(ptr_ptr); // warning will trigger here
+ return 0;
+ }
+
+In this example, ``foo()`` is called with ``ptr_ptr`` as its argument. However,
+``ptr_ptr`` is a ``int**`` pointer, while ``foo()`` expects a ``void*`` pointer.
+This results in an implicit pointer level conversion, which could cause issues
+if ``foo()`` dereferences the pointer assuming it's a ``int*`` pointer.
+
+Using an explicit cast is a recommended solution to prevent issues caused by
+implicit pointer level conversion, as it allows the developer to explicitly
+state their intention and show their reasoning for the type conversion.
+Additionally, it is recommended that developers thoroughly check and verify the
+safety of the conversion before using an explicit cast.
+This extra level of caution can help catch potential issues early on in the
+development process, improving the overall reliability and maintainability of
+the code.
Index: clang-tools-extra/docs/ReleaseNotes.rst
===================================================================
--- clang-tools-extra/docs/ReleaseNotes.rst
+++ clang-tools-extra/docs/ReleaseNotes.rst
@@ -106,6 +106,12 @@
New checks
^^^^^^^^^^
+- New :doc:`bugprone-multi-level-implicit-pointer-conversion
+ <clang-tidy/checks/bugprone/multi-level-implicit-pointer-conversion>` check.
+
+ Detects implicit conversions between pointers of different levels of
+ indirection.
+
- New :doc:`bugprone-non-zero-enum-to-bool-conversion
<clang-tidy/checks/bugprone/non-zero-enum-to-bool-conversion>` check.
Index: clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.h
===================================================================
--- /dev/null
+++ clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.h
@@ -0,0 +1,33 @@
+//===--- MultiLevelImplicitPointerConversionCheck.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_MULTILEVELIMPLICITPOINTERCONVERSIONCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MULTILEVELIMPLICITPOINTERCONVERSIONCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::bugprone {
+
+/// Detects implicit conversions between pointers of different levels of
+/// indirection.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone/multi-level-implicit-pointer-conversion.html
+class MultiLevelImplicitPointerConversionCheck : public ClangTidyCheck {
+public:
+ MultiLevelImplicitPointerConversionCheck(StringRef Name,
+ ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+ std::optional<TraversalKind> getCheckTraversalKind() const override;
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MULTILEVELIMPLICITPOINTERCONVERSIONCHECK_H
Index: clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.cpp
@@ -0,0 +1,78 @@
+//===--- MultiLevelImplicitPointerConversionCheck.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 "MultiLevelImplicitPointerConversionCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+static unsigned getPointerLevel(const QualType &PtrType) {
+ if (!PtrType->isPointerType())
+ return 0U;
+
+ return 1U + getPointerLevel(PtrType->castAs<PointerType>()->getPointeeType());
+}
+
+namespace {
+
+AST_MATCHER(ImplicitCastExpr, isMultiLevelPointerConversion) {
+ const QualType TargetType = Node.getType()
+ .getCanonicalType()
+ .getNonReferenceType()
+ .getUnqualifiedType();
+ const QualType SourceType = Node.getSubExpr()
+ ->getType()
+ .getCanonicalType()
+ .getNonReferenceType()
+ .getUnqualifiedType();
+
+ if (TargetType == SourceType)
+ return false;
+
+ const unsigned TargetPtrLevel = getPointerLevel(TargetType);
+ if (0U == TargetPtrLevel)
+ return false;
+
+ const unsigned SourcePtrLevel = getPointerLevel(SourceType);
+ if (!SourcePtrLevel)
+ return false;
+
+ return SourcePtrLevel != TargetPtrLevel;
+}
+
+} // namespace
+
+void MultiLevelImplicitPointerConversionCheck::registerMatchers(
+ MatchFinder *Finder) {
+ Finder->addMatcher(
+ implicitCastExpr(hasCastKind(CK_BitCast), isMultiLevelPointerConversion())
+ .bind("expr"),
+ this);
+}
+
+std::optional<TraversalKind>
+MultiLevelImplicitPointerConversionCheck::getCheckTraversalKind() const {
+ return TK_AsIs;
+}
+
+void MultiLevelImplicitPointerConversionCheck::check(
+ const MatchFinder::MatchResult &Result) {
+ const auto *MatchedExpr = Result.Nodes.getNodeAs<ImplicitCastExpr>("expr");
+ QualType Target = MatchedExpr->getType().getDesugaredType(*Result.Context);
+ QualType Source =
+ MatchedExpr->getSubExpr()->getType().getDesugaredType(*Result.Context);
+
+ diag(MatchedExpr->getExprLoc(), "multilevel pointer conversion from %0 to "
+ "%1, please use explicit cast")
+ << Source << Target;
+}
+
+} // namespace clang::tidy::bugprone
Index: clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
+++ clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
@@ -31,6 +31,7 @@
MisplacedPointerArithmeticInAllocCheck.cpp
MisplacedWideningCastCheck.cpp
MoveForwardingReferenceCheck.cpp
+ MultiLevelImplicitPointerConversionCheck.cpp
MultipleStatementMacroCheck.cpp
NoEscapeCheck.cpp
NonZeroEnumToBoolConversionCheck.cpp
Index: clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
+++ clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -36,6 +36,7 @@
#include "MisplacedPointerArithmeticInAllocCheck.h"
#include "MisplacedWideningCastCheck.h"
#include "MoveForwardingReferenceCheck.h"
+#include "MultiLevelImplicitPointerConversionCheck.h"
#include "MultipleStatementMacroCheck.h"
#include "NoEscapeCheck.h"
#include "NonZeroEnumToBoolConversionCheck.h"
@@ -133,6 +134,8 @@
"bugprone-misplaced-widening-cast");
CheckFactories.registerCheck<MoveForwardingReferenceCheck>(
"bugprone-move-forwarding-reference");
+ CheckFactories.registerCheck<MultiLevelImplicitPointerConversionCheck>(
+ "bugprone-multi-level-implicit-pointer-conversion");
CheckFactories.registerCheck<MultipleStatementMacroCheck>(
"bugprone-multiple-statement-macro");
CheckFactories.registerCheck<RedundantBranchConditionCheck>(
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