https://github.com/carlosgalvezp created
https://github.com/llvm/llvm-project/pull/106784
…ugh-void
reinterpret_cast is the equivalent construct, and more clearly expresses intent.
>From d3f0a650d7e3ad5bc8134e4c1fbb84ccb82d5105 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20G=C3=A1lvez?= <carlos.gal...@zenseact.com>
Date: Fri, 30 Aug 2024 19:17:16 +0000
Subject: [PATCH] [clang-tidy] Suggest using reinterpret_cast in
bugpronge-casting-through-void
reinterpret_cast is the equivalent construct, and more clearly
expresses intent.
---
.../bugprone/CastingThroughVoidCheck.cpp | 4 +-
clang-tools-extra/docs/ReleaseNotes.rst | 4 ++
.../checks/bugprone/casting-through-void.rst | 20 +++++++++-
.../bugprone/casting-through-void.cpp | 40 +++++++++----------
4 files changed, 45 insertions(+), 23 deletions(-)
diff --git a/clang-tools-extra/clang-tidy/bugprone/CastingThroughVoidCheck.cpp
b/clang-tools-extra/clang-tidy/bugprone/CastingThroughVoidCheck.cpp
index 9e714b4be4dfea..f0a9ace2297406 100644
--- a/clang-tools-extra/clang-tidy/bugprone/CastingThroughVoidCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/CastingThroughVoidCheck.cpp
@@ -38,7 +38,9 @@ void CastingThroughVoidCheck::check(const
MatchFinder::MatchResult &Result) {
const auto ST = *Result.Nodes.getNodeAs<QualType>("source_type");
const auto VT = *Result.Nodes.getNodeAs<QualType>("void_type");
const auto *CE = Result.Nodes.getNodeAs<ExplicitCastExpr>("cast");
- diag(CE->getExprLoc(), "do not cast %0 to %1 through %2") << ST << TT << VT;
+ diag(CE->getExprLoc(),
+ "do not cast %0 to %1 through %2; use reinterpret_cast instead")
+ << ST << TT << VT;
}
} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index b001a6ad446695..6999c1ef2ea4b0 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
^^^^^^^^^^^^^^^^^^^^^^^^^^
+- Improved :doc:`bugprone-casting-through-void
+ <clang-tidy/checks/bugprone/casting-through-void>` check to suggest replacing
+ the offending code with ``reinterpret_cast``, to more clearly express intent.
+
- 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/bugprone/casting-through-void.rst
b/clang-tools-extra/docs/clang-tidy/checks/bugprone/casting-through-void.rst
index a9ab478b9a82e1..05125ae7bdc8ee 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/bugprone/casting-through-void.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone/casting-through-void.rst
@@ -3,7 +3,9 @@
bugprone-casting-through-void
=============================
-Detects unsafe or redundant two-step casting operations involving ``void*``.
+Detects unsafe or redundant two-step casting operations involving ``void*``,
+which is equivalent to ``reinterpret_cast`` as per the
+`C++ Standard <https://eel.is/c++draft/expr.reinterpret.cast#7>`_.
Two-step type conversions via ``void*`` are discouraged for several reasons.
@@ -16,7 +18,16 @@ Two-step type conversions via ``void*`` are discouraged for
several reasons.
In summary, avoiding two-step type conversions through ``void*`` ensures
clearer code,
maintains essential compiler warnings, and prevents ambiguity and potential
runtime
-errors, particularly in complex inheritance scenarios.
+errors, particularly in complex inheritance scenarios. If such a cast is
wanted,
+it shall be done via ``reinterpret_cast``, to express the intent more clearly.
+
+Note: it is expected that, after applying the suggested fix and using
+``reinterpret_cast``, the check ``cppcoreguidelines-pro-type-reinterpret-cast``
+will emit a warning. This is intentional: ``reinterpret_cast`` is a dangerous
+operation that can easily break the strict aliasing rules when dereferencing
+the casted pointer, invoking Undefined Behavior. The warning is there to
+prompt users to carefuly analyze whether the usage of ``reinterpret_cast`` is
+safe, in which case the warning may be suppressed.
Examples:
@@ -29,3 +40,8 @@ Examples:
reinterpret_cast<IntegerPointer>(reinterpret_cast<void *>(ptr)); // WRONG
(IntegerPointer)(void *)ptr; // WRONG
IntegerPointer(static_cast<void *>(ptr)); // WRONG
+
+ reinterpret_cast<IntegerPointer>(ptr); // OK, clearly expresses intent.
+ // NOTE: dereferencing this pointer
violates
+ // the strict aliasing rules,
invoking
+ // Undefined Behavior.
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/casting-through-void.cpp
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/casting-through-void.cpp
index a784e498858738..68172212904f8a 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/casting-through-void.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/casting-through-void.cpp
@@ -10,42 +10,42 @@ const double cd = 100;
void normal_test() {
static_cast<int *>(static_cast<void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<int *>(static_cast<V>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'V' (aka 'void *') [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'V' (aka 'void *'); use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<int *>(static_cast<void *>(&i));
- // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'int *' to 'int *'
through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'int *' to 'int *'
through 'void *'; use reinterpret_cast instead [bugprone-casting-through-void]
static_cast<void *>(static_cast<void *>(&i));
}
void const_pointer_test() {
static_cast<int *const>(static_cast<void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*const' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*const' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<int *const>(static_cast<V>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*const' through 'V' (aka 'void *') [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*const' through 'V' (aka 'void *'); use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<int *const>(static_cast<void *>(&i));
- // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'int *' to 'int
*const' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'int *' to 'int
*const' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<void *const>(static_cast<void *>(&i));
}
void const_test() {
static_cast<const int *>(static_cast<const void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'double *' to
'const int *' through 'const void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'double *' to
'const int *' through 'const void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<const int *>(static_cast<const V>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'double *' to
'const int *' through 'const V' (aka 'void *const')
[bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'double *' to
'const int *' through 'const V' (aka 'void *const'); use reinterpret_cast
instead [bugprone-casting-through-void]
static_cast<const int *>(static_cast<const void *>(&i));
- // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'int *' to 'const
int *' through 'const void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'int *' to 'const
int *' through 'const void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<const void *>(static_cast<const void *>(&i));
static_cast<const int *>(static_cast<const void *>(&cd));
- // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'const double *' to
'const int *' through 'const void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'const double *' to
'const int *' through 'const void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<const int *>(static_cast<const CV>(&cd));
- // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'const double *' to
'const int *' through 'const CV' (aka 'const void *const')
[bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'const double *' to
'const int *' through 'const CV' (aka 'const void *const'); use
reinterpret_cast instead [bugprone-casting-through-void]
static_cast<const int *>(static_cast<const void *>(&ci));
- // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'const int *' to
'const int *' through 'const void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: do not cast 'const int *' to
'const int *' through 'const void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<const void *>(static_cast<const void *>(&ci));
}
@@ -53,11 +53,11 @@ void const_test() {
void reinterpret_cast_test() {
static_cast<int *>(reinterpret_cast<void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
reinterpret_cast<int *>(static_cast<void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
reinterpret_cast<int *>(reinterpret_cast<void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<void *>(reinterpret_cast<void *>(&i));
reinterpret_cast<void *>(reinterpret_cast<void *>(&i));
@@ -66,11 +66,11 @@ void reinterpret_cast_test() {
void c_style_cast_test() {
static_cast<int *>((void *)&d);
- // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
(int *)(void *)&d;
- // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<int *>((void *)&d);
- // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
static_cast<void *>((void *)&i);
}
@@ -82,12 +82,12 @@ using I = int *;
void cxx_functional_cast() {
A(static_cast<void*>(&d));
I(static_cast<void*>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not cast 'double *' to 'I'
(aka 'int *') through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not cast 'double *' to 'I'
(aka 'int *') through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
}
void bit_cast() {
__builtin_bit_cast(int *, static_cast<void *>(&d));
- // CHECK-MESSAGES: :[[@LINE-1]]:29: warning: do not cast 'double *' to 'int
*' through 'void *' [bugprone-casting-through-void]
+ // CHECK-MESSAGES: :[[@LINE-1]]:29: warning: do not cast 'double *' to 'int
*' through 'void *'; use reinterpret_cast instead
[bugprone-casting-through-void]
}
namespace PR87069 {
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