[clang-tools-extra] 56762b7 - [clang-tidy] Add new check bugprone-unintended-char-ostream-output (#127720)
via cfe-commits
cfe-commits at lists.llvm.org
Thu Feb 27 03:36:28 PST 2025
Author: Congcong Cai
Date: 2025-02-27T19:36:24+08:00
New Revision: 56762b7ace0596404e5ae271f278cf7540b374f2
URL: https://github.com/llvm/llvm-project/commit/56762b7ace0596404e5ae271f278cf7540b374f2
DIFF: https://github.com/llvm/llvm-project/commit/56762b7ace0596404e5ae271f278cf7540b374f2.diff
LOG: [clang-tidy] Add new check bugprone-unintended-char-ostream-output (#127720)
It wants to find unintended character output from `uint8_t` and `int8_t`
to an ostream.
e.g.
```c++
uint8_t v = 9;
std::cout << v;
```
---------
Co-authored-by: whisperity <whisperity at gmail.com>
Added:
clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.cpp
clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.h
clang-tools-extra/docs/clang-tidy/checks/bugprone/unintended-char-ostream-output.rst
clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output-cast-type.cpp
clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output.cpp
Modified:
clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
clang-tools-extra/docs/ReleaseNotes.rst
clang-tools-extra/docs/clang-tidy/checks/list.rst
Removed:
################################################################################
diff --git a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
index c5f0b5b28418f..0a3376949b6e5 100644
--- a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -90,6 +90,7 @@
#include "UndelegatedConstructorCheck.h"
#include "UnhandledExceptionAtNewCheck.h"
#include "UnhandledSelfAssignmentCheck.h"
+#include "UnintendedCharOstreamOutputCheck.h"
#include "UniquePtrArrayMismatchCheck.h"
#include "UnsafeFunctionsCheck.h"
#include "UnusedLocalNonTrivialVariableCheck.h"
@@ -147,6 +148,8 @@ class BugproneModule : public ClangTidyModule {
"bugprone-incorrect-enable-if");
CheckFactories.registerCheck<IncorrectEnableSharedFromThisCheck>(
"bugprone-incorrect-enable-shared-from-this");
+ CheckFactories.registerCheck<UnintendedCharOstreamOutputCheck>(
+ "bugprone-unintended-char-ostream-output");
CheckFactories.registerCheck<ReturnConstRefFromParameterCheck>(
"bugprone-return-const-ref-from-parameter");
CheckFactories.registerCheck<SwitchMissingDefaultCaseCheck>(
diff --git a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt b/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
index cad6b456fc268..dab139b77c770 100644
--- a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
@@ -29,6 +29,7 @@ add_clang_library(clangTidyBugproneModule STATIC
InaccurateEraseCheck.cpp
IncorrectEnableIfCheck.cpp
IncorrectEnableSharedFromThisCheck.cpp
+ UnintendedCharOstreamOutputCheck.cpp
ReturnConstRefFromParameterCheck.cpp
SuspiciousStringviewDataUsageCheck.cpp
SwitchMissingDefaultCaseCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.cpp
new file mode 100644
index 0000000000000..7250e4ccb8c69
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.cpp
@@ -0,0 +1,91 @@
+//===--- UnintendedCharOstreamOutputCheck.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 "UnintendedCharOstreamOutputCheck.h"
+#include "clang/AST/Type.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Tooling/FixIt.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+// check if the type is unsigned char or signed char
+AST_MATCHER(Type, isNumericChar) {
+ return Node.isSpecificBuiltinType(BuiltinType::SChar) ||
+ Node.isSpecificBuiltinType(BuiltinType::UChar);
+}
+
+// check if the type is char
+AST_MATCHER(Type, isChar) {
+ return Node.isSpecificBuiltinType(BuiltinType::Char_S) ||
+ Node.isSpecificBuiltinType(BuiltinType::Char_U);
+}
+
+} // namespace
+
+UnintendedCharOstreamOutputCheck::UnintendedCharOstreamOutputCheck(
+ StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context), CastTypeName(Options.get("CastTypeName")) {
+}
+void UnintendedCharOstreamOutputCheck::storeOptions(
+ ClangTidyOptions::OptionMap &Opts) {
+ if (CastTypeName.has_value())
+ Options.store(Opts, "CastTypeName", CastTypeName.value());
+}
+
+void UnintendedCharOstreamOutputCheck::registerMatchers(MatchFinder *Finder) {
+ auto BasicOstream =
+ cxxRecordDecl(hasName("::std::basic_ostream"),
+ // only basic_ostream<char, Traits> has overload operator<<
+ // with char / unsigned char / signed char
+ classTemplateSpecializationDecl(
+ hasTemplateArgument(0, refersToType(isChar()))));
+ Finder->addMatcher(
+ cxxOperatorCallExpr(
+ hasOverloadedOperatorName("<<"),
+ hasLHS(hasType(hasUnqualifiedDesugaredType(
+ recordType(hasDeclaration(cxxRecordDecl(
+ anyOf(BasicOstream, isDerivedFrom(BasicOstream)))))))),
+ hasRHS(hasType(hasUnqualifiedDesugaredType(isNumericChar()))))
+ .bind("x"),
+ this);
+}
+
+void UnintendedCharOstreamOutputCheck::check(
+ const MatchFinder::MatchResult &Result) {
+ const auto *Call = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("x");
+ const Expr *Value = Call->getArg(1);
+ const SourceRange SourceRange = Value->getSourceRange();
+
+ DiagnosticBuilder Builder =
+ diag(Call->getOperatorLoc(),
+ "%0 passed to 'operator<<' outputs as character instead of integer. "
+ "cast to 'unsigned int' to print numeric value or cast to 'char' to "
+ "print as character")
+ << Value->getType() << SourceRange;
+
+ QualType T = Value->getType();
+ const Type *UnqualifiedDesugaredType = T->getUnqualifiedDesugaredType();
+
+ llvm::StringRef CastType = CastTypeName.value_or(
+ UnqualifiedDesugaredType->isSpecificBuiltinType(BuiltinType::SChar)
+ ? "int"
+ : "unsigned int");
+
+ Builder << FixItHint::CreateReplacement(
+ SourceRange, ("static_cast<" + CastType + ">(" +
+ tooling::fixit::getText(*Value, *Result.Context) + ")")
+ .str());
+}
+
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.h b/clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.h
new file mode 100644
index 0000000000000..61ea623d139ea
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/UnintendedCharOstreamOutputCheck.h
@@ -0,0 +1,38 @@
+//===--- UnintendedCharOstreamOutputCheck.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_UNINTENDEDCHAROSTREAMOUTPUTCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNINTENDEDCHAROSTREAMOUTPUTCHECK_H
+
+#include "../ClangTidyCheck.h"
+#include <optional>
+
+namespace clang::tidy::bugprone {
+
+/// Finds unintended character output from `unsigned char` and `signed char` to
+/// an ostream.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone/unintended-char-ostream-output.html
+class UnintendedCharOstreamOutputCheck : public ClangTidyCheck {
+public:
+ UnintendedCharOstreamOutputCheck(StringRef Name, ClangTidyContext *Context);
+ void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+ bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+ return LangOpts.CPlusPlus;
+ }
+
+private:
+ const std::optional<StringRef> CastTypeName;
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNINTENDEDCHAROSTREAMOUTPUTCHECK_H
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index b87ea491b3ad1..1a68a3d182e04 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -91,6 +91,12 @@ Improvements to clang-tidy
New checks
^^^^^^^^^^
+- New :doc:`bugprone-unintended-char-ostream-output
+ <clang-tidy/checks/bugprone/unintended-char-ostream-output>` check.
+
+ Finds unintended character output from ``unsigned char`` and ``signed char`` to an
+ ``ostream``.
+
New check aliases
^^^^^^^^^^^^^^^^^
diff --git a/clang-tools-extra/docs/clang-tidy/checks/bugprone/unintended-char-ostream-output.rst b/clang-tools-extra/docs/clang-tidy/checks/bugprone/unintended-char-ostream-output.rst
new file mode 100644
index 0000000000000..ea1051847129b
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone/unintended-char-ostream-output.rst
@@ -0,0 +1,45 @@
+.. title:: clang-tidy - bugprone-unintended-char-ostream-output
+
+bugprone-unintended-char-ostream-output
+=======================================
+
+Finds unintended character output from ``unsigned char`` and ``signed char`` to an
+``ostream``.
+
+Normally, when ``unsigned char (uint8_t)`` or ``signed char (int8_t)`` is used, it
+is more likely a number than a character. However, when it is passed directly to
+``std::ostream``'s ``operator<<``, the result is the character output instead
+of the numeric value. This often contradicts the developer's intent to print
+integer values.
+
+.. code-block:: c++
+
+ uint8_t v = 65;
+ std::cout << v; // output 'A' instead of '65'
+
+The check will suggest casting the value to an appropriate type to indicate the
+intent, by default, it will cast to ``unsigned int`` for ``unsigned char`` and
+``int`` for ``signed char``.
+
+.. code-block:: c++
+
+ std::cout << static_cast<unsigned int>(v); // when v is unsigned char
+ std::cout << static_cast<int>(v); // when v is signed char
+
+To avoid lengthy cast statements, add prefix ``+`` to the variable can also
+suppress warnings because unary expression will promote the value to an ``int``.
+
+.. code-block:: c++
+
+ std::cout << +v;
+
+Or cast to char to explicitly indicate that output should be a character.
+
+.. code-block:: c++
+
+ std::cout << static_cast<char>(v);
+
+.. option:: CastTypeName
+
+ When `CastTypeName` is specified, the fix-it will use `CastTypeName` as the
+ cast target type. Otherwise, fix-it will automatically infer the type.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index 7b9b905ef7671..5f03ef72cc603 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -158,6 +158,7 @@ Clang-Tidy Checks
:doc:`bugprone-undelegated-constructor <bugprone/undelegated-constructor>`,
:doc:`bugprone-unhandled-exception-at-new <bugprone/unhandled-exception-at-new>`,
:doc:`bugprone-unhandled-self-assignment <bugprone/unhandled-self-assignment>`,
+ :doc:`bugprone-unintended-char-ostream-output <bugprone/unintended-char-ostream-output>`, "Yes"
:doc:`bugprone-unique-ptr-array-mismatch <bugprone/unique-ptr-array-mismatch>`, "Yes"
:doc:`bugprone-unsafe-functions <bugprone/unsafe-functions>`,
:doc:`bugprone-unused-local-non-trivial-variable <bugprone/unused-local-non-trivial-variable>`,
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output-cast-type.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output-cast-type.cpp
new file mode 100644
index 0000000000000..faea4127ac44a
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output-cast-type.cpp
@@ -0,0 +1,45 @@
+// RUN: %check_clang_tidy %s bugprone-unintended-char-ostream-output %t -- \
+// RUN: -config="{CheckOptions: \
+// RUN: {bugprone-unintended-char-ostream-output.CastTypeName: "uint8_t"}}"
+
+namespace std {
+
+template <class _CharT, class _Traits = void> class basic_ostream {
+public:
+ basic_ostream &operator<<(int);
+ basic_ostream &operator<<(unsigned int);
+};
+
+template <class CharT, class Traits>
+basic_ostream<CharT, Traits> &operator<<(basic_ostream<CharT, Traits> &, CharT);
+template <class CharT, class Traits>
+basic_ostream<CharT, Traits> &operator<<(basic_ostream<CharT, Traits> &, char);
+template <class _Traits>
+basic_ostream<char, _Traits> &operator<<(basic_ostream<char, _Traits> &, char);
+template <class _Traits>
+basic_ostream<char, _Traits> &operator<<(basic_ostream<char, _Traits> &,
+ signed char);
+template <class _Traits>
+basic_ostream<char, _Traits> &operator<<(basic_ostream<char, _Traits> &,
+ unsigned char);
+
+using ostream = basic_ostream<char>;
+
+} // namespace std
+
+class A : public std::ostream {};
+
+void origin_ostream(std::ostream &os) {
+ unsigned char unsigned_value = 9;
+ os << unsigned_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<uint8_t>(unsigned_value);
+
+ signed char signed_value = 9;
+ os << signed_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'signed char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<uint8_t>(signed_value);
+
+ char char_value = 9;
+ os << char_value;
+}
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output.cpp
new file mode 100644
index 0000000000000..0a5cdeb21c01e
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unintended-char-ostream-output.cpp
@@ -0,0 +1,131 @@
+// RUN: %check_clang_tidy %s bugprone-unintended-char-ostream-output %t
+
+namespace std {
+
+template <class _CharT, class _Traits = void> class basic_ostream {
+public:
+ basic_ostream &operator<<(int);
+ basic_ostream &operator<<(unsigned int);
+};
+
+template <class CharT, class Traits>
+basic_ostream<CharT, Traits> &operator<<(basic_ostream<CharT, Traits> &, CharT);
+template <class CharT, class Traits>
+basic_ostream<CharT, Traits> &operator<<(basic_ostream<CharT, Traits> &, char);
+template <class _Traits>
+basic_ostream<char, _Traits> &operator<<(basic_ostream<char, _Traits> &, char);
+template <class _Traits>
+basic_ostream<char, _Traits> &operator<<(basic_ostream<char, _Traits> &,
+ signed char);
+template <class _Traits>
+basic_ostream<char, _Traits> &operator<<(basic_ostream<char, _Traits> &,
+ unsigned char);
+
+using ostream = basic_ostream<char>;
+
+} // namespace std
+
+class A : public std::ostream {};
+
+void origin_ostream(std::ostream &os) {
+ unsigned char unsigned_value = 9;
+ os << unsigned_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(unsigned_value);
+
+ signed char signed_value = 9;
+ os << signed_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'signed char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<int>(signed_value);
+
+ char char_value = 9;
+ os << char_value;
+}
+
+void based_on_ostream(A &os) {
+ unsigned char unsigned_value = 9;
+ os << unsigned_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(unsigned_value);
+
+ signed char signed_value = 9;
+ os << signed_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'signed char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<int>(signed_value);
+
+ char char_value = 9;
+ os << char_value;
+}
+
+void based_on_ostream(std::basic_ostream<unsigned char> &os) {
+ unsigned char unsigned_value = 9;
+ os << unsigned_value;
+
+ signed char signed_value = 9;
+ os << signed_value;
+
+ char char_value = 9;
+ os << char_value;
+}
+
+template <class T> class B : public std::ostream {};
+void template_based_on_ostream(B<int> &os) {
+ unsigned char unsigned_value = 9;
+ os << unsigned_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(unsigned_value);
+}
+
+template<class T> void template_fn_1(T &os) {
+ unsigned char unsigned_value = 9;
+ os << unsigned_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(unsigned_value);
+}
+template<class T> void template_fn_2(std::ostream &os) {
+ T unsigned_value = 9;
+ os << unsigned_value;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(unsigned_value);
+}
+template<class T> void template_fn_3(std::ostream &os) {
+ T unsigned_value = 9;
+ os << unsigned_value;
+}
+void call_template_fn() {
+ A a{};
+ template_fn_1(a);
+ template_fn_2<unsigned char>(a);
+ template_fn_3<char>(a);
+}
+
+using U8 = unsigned char;
+void alias_unsigned_char(std::ostream &os) {
+ U8 v = 9;
+ os << v;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'U8' (aka 'unsigned char') passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(v);
+}
+
+using I8 = signed char;
+void alias_signed_char(std::ostream &os) {
+ I8 v = 9;
+ os << v;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'I8' (aka 'signed char') passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<int>(v);
+}
+
+using C8 = char;
+void alias_char(std::ostream &os) {
+ C8 v = 9;
+ os << v;
+}
+
+
+#define MACRO_VARIANT_NAME a
+void macro_variant_name(std::ostream &os) {
+ unsigned char MACRO_VARIANT_NAME = 9;
+ os << MACRO_VARIANT_NAME;
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: 'unsigned char' passed to 'operator<<' outputs as character instead of integer
+ // CHECK-FIXES: os << static_cast<unsigned int>(MACRO_VARIANT_NAME);
+}
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