[clang-tools-extra] [clang-tidy] Improved cppcoreguidelines-pro-type-const-cast (PR #69501)
Piotr Zegar via cfe-commits
cfe-commits at lists.llvm.org
Wed Oct 18 12:15:04 PDT 2023
https://github.com/PiotrZSL created https://github.com/llvm/llvm-project/pull/69501
Improved cppcoreguidelines-pro-type-const-cast check to ignore casts to const type (controlled by option) and casts in implicitly invoked code.
Fixes #69319
>From ada6ee07f310ce482ef0cb0339b25db6e31d8c13 Mon Sep 17 00:00:00 2001
From: Piotr Zegar <me at piotrzegar.pl>
Date: Wed, 18 Oct 2023 19:10:32 +0000
Subject: [PATCH] [clang-tidy] Improved cppcoreguidelines-pro-type-const-cast
Improved cppcoreguidelines-pro-type-const-cast check to ignore
casts to const type (controlled by option) and casts in
implicitly invoked code.
---
.../ProTypeConstCastCheck.cpp | 33 +++++++++++++++++--
.../cppcoreguidelines/ProTypeConstCastCheck.h | 12 +++++--
clang-tools-extra/docs/ReleaseNotes.rst | 5 +++
.../cppcoreguidelines/pro-type-const-cast.rst | 24 +++++++++++---
.../cppcoreguidelines/pro-type-const-cast.cpp | 28 ++++++++++++++--
.../nonstandard-file-extension.test | 2 +-
6 files changed, 91 insertions(+), 13 deletions(-)
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp
index ef803ab85fa0841..4661c7d072f9256 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp
@@ -14,13 +14,42 @@ using namespace clang::ast_matchers;
namespace clang::tidy::cppcoreguidelines {
+static bool hasConstQualifier(QualType Type) {
+ const QualType PtrType = Type->getPointeeType();
+ if (!PtrType.isNull())
+ return hasConstQualifier(PtrType);
+
+ return Type.isConstQualified();
+}
+
+namespace {
+AST_MATCHER(QualType, hasConst) { return hasConstQualifier(Node); }
+} // namespace
+
+ProTypeConstCastCheck::ProTypeConstCastCheck(StringRef Name,
+ ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context),
+ StrictMode(Options.getLocalOrGlobal("StrictMode", false)) {}
+
+void ProTypeConstCastCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+ Options.store(Opts, "StrictMode", StrictMode);
+}
+
void ProTypeConstCastCheck::registerMatchers(MatchFinder *Finder) {
- Finder->addMatcher(cxxConstCastExpr().bind("cast"), this);
+ if (StrictMode)
+ Finder->addMatcher(cxxConstCastExpr().bind("cast"), this);
+ else
+ Finder->addMatcher(cxxConstCastExpr(unless(hasDestinationType(
+ hasCanonicalType(hasConst()))))
+ .bind("cast"),
+ this);
}
void ProTypeConstCastCheck::check(const MatchFinder::MatchResult &Result) {
const auto *MatchedCast = Result.Nodes.getNodeAs<CXXConstCastExpr>("cast");
- diag(MatchedCast->getOperatorLoc(), "do not use const_cast");
+ diag(MatchedCast->getOperatorLoc(),
+ "do not use const_cast%select{ to cast away const|}0")
+ << StrictMode;
}
} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h
index f7ae9bbb60dcda3..8d93633a321b53f 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h
@@ -13,19 +13,25 @@
namespace clang::tidy::cppcoreguidelines {
-/// This check flags all instances of const_cast
+/// Imposes limitations on the use of const_cast within C++ code.
///
/// For the user-facing documentation see:
/// http://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines/pro-type-const-cast.html
class ProTypeConstCastCheck : public ClangTidyCheck {
public:
- ProTypeConstCastCheck(StringRef Name, ClangTidyContext *Context)
- : ClangTidyCheck(Name, Context) {}
+ ProTypeConstCastCheck(StringRef Name, ClangTidyContext *Context);
bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
return LangOpts.CPlusPlus;
}
void registerMatchers(ast_matchers::MatchFinder *Finder) override;
void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+ void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+ std::optional<TraversalKind> getCheckTraversalKind() const override {
+ return TK_IgnoreUnlessSpelledInSource;
+ }
+
+private:
+ const bool StrictMode;
};
} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 3e1fbe091c9ff6a..0a9f6691ff68516 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -236,6 +236,11 @@ Changes in existing checks
<clang-tidy/checks/cppcoreguidelines/pro-bounds-constant-array-index>` check
to perform checks on derived classes of ``std::array``.
+- Improved :doc:`cppcoreguidelines-pro-type-const-cast
+ <clang-tidy/checks/cppcoreguidelines/pro-type-const-cast>` check to ignore
+ casts to ``const`` type (controlled by `StrictMode` option) and casts in
+ implicitly invoked code.
+
- Improved :doc:`cppcoreguidelines-pro-type-member-init
<clang-tidy/checks/cppcoreguidelines/pro-type-member-init>` check to ignore
dependent delegate constructors.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-const-cast.rst b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-const-cast.rst
index eb572e625f12977..6db8f6a2efd3535 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-const-cast.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-const-cast.rst
@@ -3,11 +3,27 @@
cppcoreguidelines-pro-type-const-cast
=====================================
-This check flags all uses of ``const_cast`` in C++ code.
+Imposes limitations on the use of ``const_cast`` within C++ code. It depends on
+the :option:`StrictMode` option setting to determine whether it should flag all
+instances of ``const_cast`` or only those that remove the ``const`` qualifier.
-Modifying a variable that was declared const is undefined behavior, even with
-``const_cast``.
+Modifying a variable that has been declared as ``const`` in C++ is generally
+considered undefined behavior, and this remains true even when using
+``const_cast``. In C++, the ``const`` qualifier indicates that a variable is
+intended to be read-only, and the compiler enforces this by disallowing any
+attempts to change the value of that variable.
This rule is part of the `Type safety (Type 3)
<https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Pro-type-constcast>`_
-profile from the C++ Core Guidelines.
+profile and `ES.50: Don’t cast away const
+<https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#es50-dont-cast-away-const>`_
+rule from the C++ Core Guidelines.
+
+Options
+-------
+
+.. option:: StrictMode
+
+ When this setting is set to `true`, it means that any usage of ``const_cast``
+ is not allowed. On the other hand, when it's set to `false`, it permits
+ casting to ``const`` types. By default, this setting is `false`.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-const-cast.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-const-cast.cpp
index 2d32e13723abf83..8f48082b6274fce 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-const-cast.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-const-cast.cpp
@@ -1,6 +1,28 @@
-// RUN: %check_clang_tidy %s cppcoreguidelines-pro-type-const-cast %t
+// RUN: %check_clang_tidy -check-suffix=STRICT %s cppcoreguidelines-pro-type-const-cast %t -- -config="{CheckOptions: {StrictMode: true}}"
+// RUN: %check_clang_tidy -check-suffix=NSTRICT %s cppcoreguidelines-pro-type-const-cast %t
const int *i;
int *j;
-void f() { j = const_cast<int *>(i); }
-// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+
+void f() {
+ j = const_cast<int *>(i);
+ // CHECK-MESSAGES-NSTRICT: :[[@LINE-1]]:7: warning: do not use const_cast to cast away const [cppcoreguidelines-pro-type-const-cast]
+ // CHECK-MESSAGES-STRICT: :[[@LINE-2]]:7: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+
+ i = const_cast<const int*>(j);
+ // CHECK-MESSAGES-STRICT: :[[@LINE-1]]:7: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+
+ j = *const_cast<int **>(&i);
+ // CHECK-MESSAGES-NSTRICT: :[[@LINE-1]]:8: warning: do not use const_cast to cast away const [cppcoreguidelines-pro-type-const-cast]
+ // CHECK-MESSAGES-STRICT: :[[@LINE-2]]:8: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+
+ i = *const_cast<const int**>(&j);
+ // CHECK-MESSAGES-STRICT: :[[@LINE-1]]:8: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+
+ j = &const_cast<int&>(*i);
+ // CHECK-MESSAGES-NSTRICT: :[[@LINE-1]]:8: warning: do not use const_cast to cast away const [cppcoreguidelines-pro-type-const-cast]
+ // CHECK-MESSAGES-STRICT: :[[@LINE-2]]:8: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+
+ i = &const_cast<const int&>(*j);
+ // CHECK-MESSAGES-STRICT: :[[@LINE-1]]:8: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+}
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nonstandard-file-extension.test b/clang-tools-extra/test/clang-tidy/infrastructure/nonstandard-file-extension.test
index 4cb4d1171195a01..e6d81cf304bb77a 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nonstandard-file-extension.test
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nonstandard-file-extension.test
@@ -3,4 +3,4 @@
const int *i;
int *j;
void f() { j = const_cast<int *>(i); }
-// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: do not use const_cast [cppcoreguidelines-pro-type-const-cast]
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: do not use const_cast to cast away const [cppcoreguidelines-pro-type-const-cast]
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