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This checker warns for cases when pointer is cast and the pointed to type is
incompatible with allocated memory area type.
This may lead to access memory based on invalid memory layout.
Warn for cases when the pointed to type is wider than the allocated type.
For example char vs integer, long vs char etc.
Also warn for cases when the pointed to type layout is different from the
allocated type layout, like different structs, integer vs float/double,
different signedness.
Allows pointer casts if the pointed to struct type is "part" of the allocated
type.
Which means the allocated type contains the pointed to type member by member.
Repository:
rCTE Clang Tools Extra
https://reviews.llvm.org/D48866
Files:
clang-tidy/misc/CMakeLists.txt
clang-tidy/misc/IncorrectPointerCastCheck.cpp
clang-tidy/misc/IncorrectPointerCastCheck.h
clang-tidy/misc/MiscTidyModule.cpp
docs/ReleaseNotes.rst
docs/clang-tidy/checks/list.rst
docs/clang-tidy/checks/misc-incorrect-pointer-cast.rst
test/clang-tidy/misc-incorrect-pointer-cast.cpp
Index: test/clang-tidy/misc-incorrect-pointer-cast.cpp
===================================================================
--- /dev/null
+++ test/clang-tidy/misc-incorrect-pointer-cast.cpp
@@ -0,0 +1,108 @@
+// RUN: %check_clang_tidy %s misc-incorrect-pointer-cast %t -- \
+// RUN: -config="{CheckOptions: [{key: misc-incorrect-pointer-cast.WarnForDifferentSignedness, value: 1}]}" --
+
+struct S1 {
+ int a;
+ int b;
+};
+
+struct S2 {
+ int a;
+};
+
+struct S3 {
+ int a;
+ double b;
+};
+
+struct S4 {
+ int x;
+ double y;
+};
+
+struct S5 {
+ double y;
+ int x;
+};
+
+void initDouble(double *d) {
+ *d = 0.5;
+}
+
+void castCharToSort() {
+ char c;
+ short *i = (short *)&c;
+ // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: Do not use C-style cast to wider type 'short' from narrower type 'char' [misc-incorrect-pointer-cast]
+}
+
+void castShortToInt() {
+ short s;
+ int *i = (int *)&s;
+ // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: Do not use C-style cast to wider type 'int' from narrower type 'short' [misc-incorrect-pointer-cast]
+}
+
+void castWideCharToLong() {
+ wchar_t wc;
+ long *f = (long *)&wc;
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: Do not use C-style cast to wider type 'long' from narrower type 'wchar_t' [misc-incorrect-pointer-cast]
+}
+
+void castFloatToDouble() {
+ float f;
+ initDouble((double *)&f);
+ // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: Do not use C-style cast to wider type 'double' from narrower type 'float' [misc-incorrect-pointer-cast]
+}
+
+void castS3ToS1() {
+ struct S3 s3;
+ struct S1 *s1 = (struct S1 *)&s3;
+ // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: Do not use C-style cast from 'struct S3' to 'struct S1'! Different type layout. Struct members are incompatible [misc-incorrect-pointer-cast]
+}
+
+void castS4ToS5() {
+ struct S4 s4;
+ struct S5 *s5 = (struct S5 *)&s4;
+ // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: Do not use C-style cast from 'struct S4' to 'struct S5'! Different type layout. Struct members are incompatible [misc-incorrect-pointer-cast]
+}
+
+void castULongToLong() {
+ unsigned long ul;
+ long *l = (long *)&ul;
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: Do not use C-style cast to convert between different signedness types - Source Type: 'unsigned long', Destination Type: 'long' [misc-incorrect-pointer-cast]
+}
+
+void castIntToUInt() {
+ int i;
+ unsigned int *ui = (unsigned int *)&i;
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: Do not use C-style cast to convert between different signedness types - Source Type: 'int', Destination Type: 'unsigned int' [misc-incorrect-pointer-cast]
+}
+
+// negatives
+void castIntToFloat() {
+ int i;
+ float *f = (float *)&i;
+}
+
+void castShortToChar() {
+ short s;
+ char *c = (char *)&s;
+}
+
+void initInt(int *i) {
+ *i = 1;
+}
+
+void castIntToInt() {
+ int i;
+ initInt(&i);
+}
+
+void castS1ToS2() {
+ struct S1 s1;
+ struct S2 *s2 = (struct S2 *)&s1;
+}
+
+void castS4ToS3() {
+ struct S4 s4;
+ struct S3 *s3 = (struct S3 *)&s4;
+}
\ No newline at end of file
Index: docs/clang-tidy/checks/misc-incorrect-pointer-cast.rst
===================================================================
--- /dev/null
+++ docs/clang-tidy/checks/misc-incorrect-pointer-cast.rst
@@ -0,0 +1,67 @@
+.. title:: clang-tidy - misc-incorrect-pointer-cast
+
+misc-incorrect-pointer-cast
+===========================
+
+This checker warns for cases when pointer is cast and the pointed to type is
+incompatible with allocated memory area type. This may lead to access memory
+based on invalid memory layout.
+
+Warn for cases when the pointed to type is wider than the allocated type.
+For example char vs integer, long vs char etc.
+Also warn for cases when the pointed to type layout is different from the allocated type layout,
+like different structs, integer vs float/double, different signedness.
+
+Allows pointer casts if the pointed to struct type is "part" of the allocated type.
+Which means the allocated type contains the pointed to type member by member.
+
+Options
+-------
+
+.. option:: WarnForDifferentSignedness
+
+ This option can be configured to warn when the pointed to type signedness
+ is different from the allocated type. The default is false because this
+ option might be noisy on some code bases.
+
+Examles
+-------
+
+Cast char pointer to integer pointer. Check will warn because of cast to a wider type.
+
+.. code-block:: c++
+
+ char c = 'a';
+ int *i = (int *)&c;
+
+Cast between structs. Check will allow to cast to a narrower struct if it is part of the
+source struct member by member.
+
+.. code-block:: c++
+
+ struct S1 {
+ int a;
+ };
+
+ struct S2 {
+ int a;
+ double b;
+ };
+
+ struct S3 {
+ double y;
+ long x;
+ };
+
+ struct S2 s2;
+ struct S1 *s1 = (struct S1 *)&s2; // Won't warn. Struct "S2" contains struct
+ // "S2" member by member.
+ struct S3 *s3 = (struct S3 *)&s2; // Warning because of different type layout.
+
+Cast between different signedness types.
+If the `WarnForDifferentSignedness` option is `1`, check will warn for these kind of casts.
+
+.. code-block:: c++
+
+ unsigned int u;
+ int i = (int *)&u;
Index: docs/clang-tidy/checks/list.rst
===================================================================
--- docs/clang-tidy/checks/list.rst
+++ docs/clang-tidy/checks/list.rst
@@ -151,6 +151,7 @@
llvm-namespace-comment
llvm-twine-local
misc-definitions-in-headers
+ misc-incorrect-pointer-cast
misc-misplaced-const
misc-new-delete-overloads
misc-non-copyable-objects
Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -57,6 +57,13 @@
Improvements to clang-tidy
--------------------------
+- New :doc:`misc-incorrect-pointer-cast
+ <clang-tidy/checks/misc-incorrect-pointer-cast>` check
+
+ Warn for cases when pointer is cast and the pointed to type is
+ incompatible with allocated memory area type. This may lead to access memory
+ based on invalid memory layout.
+
- The checks profiling info can now be stored as JSON files for futher
post-processing and analysis.
Index: clang-tidy/misc/MiscTidyModule.cpp
===================================================================
--- clang-tidy/misc/MiscTidyModule.cpp
+++ clang-tidy/misc/MiscTidyModule.cpp
@@ -11,6 +11,7 @@
#include "../ClangTidyModule.h"
#include "../ClangTidyModuleRegistry.h"
#include "DefinitionsInHeadersCheck.h"
+#include "IncorrectPointerCastCheck.h"
#include "MisplacedConstCheck.h"
#include "NewDeleteOverloadsCheck.h"
#include "NonCopyableObjects.h"
@@ -30,6 +31,8 @@
class MiscModule : public ClangTidyModule {
public:
void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+ CheckFactories.registerCheck<IncorrectPointerCastCheck>(
+ "misc-incorrect-pointer-cast");
CheckFactories.registerCheck<MisplacedConstCheck>("misc-misplaced-const");
CheckFactories.registerCheck<UnconventionalAssignOperatorCheck>(
"misc-unconventional-assign-operator");
Index: clang-tidy/misc/IncorrectPointerCastCheck.h
===================================================================
--- /dev/null
+++ clang-tidy/misc/IncorrectPointerCastCheck.h
@@ -0,0 +1,46 @@
+//===--- IncorrectPointerCastCheck.h - clang-tidy----------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_INCORRECTPOINTERCASTCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_INCORRECTPOINTERCASTCHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+/// This checker warns for cases when pointer is cast and the pointed to type is
+/// incompatible with allocated memory area type. This may lead to access memory
+/// based on invalid memory layout.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/misc-incorrect-pointer-cast.html
+class IncorrectPointerCastCheck : public ClangTidyCheck {
+public:
+ IncorrectPointerCastCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context),
+ WarnForDifferentSignedness(
+ Options.get("WarnForDifferentSignedness", false)) {}
+ void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+ /// This option can be configured to warn when the pointed to type signedness
+ /// is different from the allocated type. The default is false because this
+ /// option might be noisy on some code bases.
+ const bool WarnForDifferentSignedness;
+};
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_INCORRECTPOINTERCASTCHECK_H
Index: clang-tidy/misc/IncorrectPointerCastCheck.cpp
===================================================================
--- /dev/null
+++ clang-tidy/misc/IncorrectPointerCastCheck.cpp
@@ -0,0 +1,84 @@
+//===--- IncorrectPointerCastCheck.cpp - clang-tidy------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "IncorrectPointerCastCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/RecordLayout.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+void IncorrectPointerCastCheck::storeOptions(
+ ClangTidyOptions::OptionMap &Opts) {
+ Options.store(Opts, "WarnForDifferentSignedness", WarnForDifferentSignedness);
+}
+
+void IncorrectPointerCastCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(cStyleCastExpr(hasCastKind(CK_BitCast),
+ unless(isInTemplateInstantiation()))
+ .bind("cast"),
+ this);
+}
+
+void IncorrectPointerCastCheck::check(const MatchFinder::MatchResult &Result) {
+ const ASTContext &Context = *Result.Context;
+ const CStyleCastExpr *CastExpr =
+ Result.Nodes.getNodeAs<CStyleCastExpr>("cast");
+ const QualType SrcType = CastExpr->getSubExpr()->getType()->getPointeeType();
+ const QualType DestType = CastExpr->getType()->getPointeeType();
+
+ if (SrcType->isStructureType() && DestType->isStructureType()) {
+ const auto *SrcTypeCXXRecordDecl = SrcType->getAsCXXRecordDecl();
+ const auto *DestTypeCXXRecordDecl = DestType->getAsCXXRecordDecl();
+ bool FieldsAreSame = true;
+
+ for (RecordDecl::field_iterator
+ SrcIterator = SrcTypeCXXRecordDecl->field_begin(),
+ SrcEnd = SrcTypeCXXRecordDecl->field_end(),
+ DestIterator = DestTypeCXXRecordDecl->field_begin(),
+ DestEnd = DestTypeCXXRecordDecl->field_end();
+ DestIterator != DestEnd && FieldsAreSame;
+ ++SrcIterator, ++DestIterator) {
+ const FieldDecl &SrcField = **SrcIterator;
+ const FieldDecl &DestField = **DestIterator;
+ if (SrcField.getType() != DestField.getType() || SrcIterator == SrcEnd) {
+ FieldsAreSame = false;
+ }
+
+ if (!FieldsAreSame) {
+ diag(CastExpr->getLocStart(),
+ "Do not use C-style cast from %0 to %1! "
+ "Different type layout. Struct members are incompatible")
+ << SrcType << DestType;
+ }
+ }
+ } else if (Context.getIntWidth(SrcType) < Context.getIntWidth(DestType)) {
+ diag(CastExpr->getLocStart(), "Do not use C-style cast to wider type %0 "
+ "from narrower type %1")
+ << DestType << SrcType;
+ } else if (WarnForDifferentSignedness &&
+ Context.getIntWidth(SrcType) == Context.getIntWidth(DestType)) {
+ if ((SrcType->isSignedIntegerType() && DestType->isUnsignedIntegerType()) ||
+ (SrcType->isUnsignedIntegerType() && DestType->isSignedIntegerType())) {
+ diag(CastExpr->getLocStart(),
+ "Do not use C-style cast to convert between "
+ "different signedness types - Source Type: %0, Destination Type: "
+ "%1")
+ << SrcType << DestType;
+ }
+ }
+} // namespace misc
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/misc/CMakeLists.txt
===================================================================
--- clang-tidy/misc/CMakeLists.txt
+++ clang-tidy/misc/CMakeLists.txt
@@ -1,6 +1,7 @@
set(LLVM_LINK_COMPONENTS support)
add_clang_library(clangTidyMiscModule
+ IncorrectPointerCastCheck.cpp
MisplacedConstCheck.cpp
UnconventionalAssignOperatorCheck.cpp
DefinitionsInHeadersCheck.cpp
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