https://github.com/carlosgalvezp created
https://github.com/llvm/llvm-project/pull/106922
…t to allow casts to byte types
These casts are safe according to the Standard, so add an option to allow them
and not emit a warning. This helps silencing some noise and focusing on the
unsafe casts.
>From 87f3bca5a4f0cdb7f560da1d11d76ee9f3ce9d0a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20G=C3=A1lvez?= <carlos.gal...@zenseact.com>
Date: Sun, 1 Sep 2024 19:14:22 +0000
Subject: [PATCH] [clang-tidy] Add option to
cppcoreguidelines-pro-type-reinterpret-cast to allow casts to byte types
These casts are safe according to the Standard, so add an option to
allow them and not emit a warning. This helps silencing some noise
and focusing on the unsafe casts.
---
.../ProTypeReinterpretCastCheck.cpp | 50 +++++++++++++++++--
.../ProTypeReinterpretCastCheck.h | 7 ++-
clang-tools-extra/docs/ReleaseNotes.rst | 4 ++
.../pro-type-reinterpret-cast.rst | 19 +++++++
.../pro-type-reinterpret-cast.cpp | 36 ++++++++++++-
5 files changed, 109 insertions(+), 7 deletions(-)
diff --git
a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
index 14456caab612b7..6385dd5440901c 100644
---
a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
+++
b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
@@ -9,20 +9,64 @@
#include "ProTypeReinterpretCastCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/STLExtras.h"
+#include <array>
+#include <string>
using namespace clang::ast_matchers;
namespace clang::tidy::cppcoreguidelines {
+static bool isCastToBytes(ASTContext const &Ctx,
+ CXXReinterpretCastExpr const &Expr) {
+ // https://eel.is/c++draft/basic.lval#11.3
+ static constexpr std::array<StringRef, 3> AllowedByteTypes = {
+ "char",
+ "unsigned char",
+ "std::byte",
+ };
+
+ // We only care about pointer casts
+ QualType DestType = Expr.getTypeAsWritten();
+ if (!DestType->isPointerType())
+ return false;
+
+ // Get the unqualified canonical type, and check if it's allowed
+ // We need to wrap the Type into a QualType to call getAsString()
+ const Type *UnqualDestType =
+ DestType.getCanonicalType()->getPointeeType().getTypePtr();
+ std::string DestTypeString = QualType(UnqualDestType, /*Quals=*/0)
+ .getAsString(Ctx.getPrintingPolicy());
+ return llvm::any_of(AllowedByteTypes, [DestTypeString](StringRef Type) {
+ return Type == DestTypeString;
+ });
+}
+
+ProTypeReinterpretCastCheck::ProTypeReinterpretCastCheck(
+ StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context),
+ AllowCastToBytes(Options.getLocalOrGlobal("AllowCastToBytes", false)) {}
+
+void ProTypeReinterpretCastCheck::storeOptions(
+ ClangTidyOptions::OptionMap &Opts) {
+ Options.store(Opts, "AllowCastToBytes", AllowCastToBytes);
+}
+
void ProTypeReinterpretCastCheck::registerMatchers(MatchFinder *Finder) {
Finder->addMatcher(cxxReinterpretCastExpr().bind("cast"), this);
}
void ProTypeReinterpretCastCheck::check(
const MatchFinder::MatchResult &Result) {
- const auto *MatchedCast =
- Result.Nodes.getNodeAs<CXXReinterpretCastExpr>("cast");
- diag(MatchedCast->getOperatorLoc(), "do not use reinterpret_cast");
+
+ if (const auto *MatchedCast =
+ Result.Nodes.getNodeAs<CXXReinterpretCastExpr>("cast")) {
+ ASTContext const &Ctx = *Result.Context;
+ if (AllowCastToBytes && isCastToBytes(Ctx, *MatchedCast))
+ return;
+
+ diag(MatchedCast->getOperatorLoc(), "do not use reinterpret_cast");
+ }
}
} // namespace clang::tidy::cppcoreguidelines
diff --git
a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
index da001bfb85d787..66b46ba7e9f5b9 100644
---
a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
+++
b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
@@ -19,13 +19,16 @@ namespace clang::tidy::cppcoreguidelines {
///
http://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines/pro-type-reinterpret-cast.html
class ProTypeReinterpretCastCheck : public ClangTidyCheck {
public:
- ProTypeReinterpretCastCheck(StringRef Name, ClangTidyContext *Context)
- : ClangTidyCheck(Name, Context) {}
+ ProTypeReinterpretCastCheck(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;
+
+private:
+ const bool AllowCastToBytes;
};
} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index b001a6ad446695..1b38a3572e02f3 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -104,6 +104,10 @@ New check aliases
Changes in existing checks
^^^^^^^^^^^^^^^^^^^^^^^^^^
+- Add option to :doc:`cppcoreguidelines-pro-type-reinterpret-cast
+ <clang-tidy/checks/cppcoreguidelines/pro-type-reinterpret-cast>` to allow
+ casting an object to its byte representation.
+
- Improved :doc:`modernize-use-std-format
<clang-tidy/checks/modernize/use-std-format>` check to support replacing
member function calls too.
diff --git
a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-reinterpret-cast.rst
b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-reinterpret-cast.rst
index a0946825156fcf..c8d9130f4f2534 100644
---
a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-reinterpret-cast.rst
+++
b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-reinterpret-cast.rst
@@ -12,3 +12,22 @@ unrelated type ``Z``.
This rule is part of the `Type safety (Type.1.1)
<https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Pro-type-reinterpretcast>`_
profile from the C++ Core Guidelines.
+
+Options
+-------
+
+.. option:: AllowCastToBytes
+
+ When this setting is set to `true`, it will not warn when casting an object
+ to its byte representation, which is safe according to the C++ Standard.
+ The allowed byte types are: ``char``, ``unsigned char`` and ``std::byte``.
+ Example:
+
+ .. code-block:: cpp
+
+ float x{};
+ auto a = reinterpret_cast<char*>(&x); // OK
+ auto b = reinterpret_cast<unsigned char*>(&x); // OK
+ auto c = reinterpret_cast<std::byte*>(&x); // OK
+
+ Default value is `false`.
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-reinterpret-cast.cpp
b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-reinterpret-cast.cpp
index 54208102e6f07f..1bfdc4b0eca7b8 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-reinterpret-cast.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-reinterpret-cast.cpp
@@ -1,6 +1,38 @@
-// RUN: %check_clang_tidy %s cppcoreguidelines-pro-type-reinterpret-cast %t
+// RUN: %check_clang_tidy -check-suffix=DEFAULT %s
cppcoreguidelines-pro-type-reinterpret-cast %t
+// RUN: %check_clang_tidy -check-suffix=ALLOW-CAST-TO-BYTES %s
cppcoreguidelines-pro-type-reinterpret-cast %t \
+// RUN: -config="{CheckOptions: { \
+// RUN:
cppcoreguidelines-pro-type-reinterpret-cast.AllowCastToBytes: True \
+// RUN: }}"
int i = 0;
void *j;
void f() { j = reinterpret_cast<void *>(i); }
-// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: do not use reinterpret_cast
[cppcoreguidelines-pro-type-reinterpret-cast]
+// CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:16: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+// CHECK-MESSAGES-ALLOW-CAST-TO-BYTES: :[[@LINE-2]]:16: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+
+namespace std
+{
+enum class byte : unsigned char
+{};
+}
+
+void check_cast_to_bytes()
+{
+ float x{};
+ auto a = reinterpret_cast<char*>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+ auto b = reinterpret_cast<char const*>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+ auto c = reinterpret_cast<unsigned char*>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+ auto d = reinterpret_cast<unsigned char const*>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+ auto e = reinterpret_cast<std::byte*>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+ auto f = reinterpret_cast<std::byte const*>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+
+ using CharPtr = char*;
+ auto g = reinterpret_cast<CharPtr>(&x);
+ // CHECK-MESSAGES-DEFAULT: :[[@LINE-1]]:12: warning: do not use
reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
+}
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