Extra Clang Tools 23.0.0git (In-Progress) Release Notes¶

Written by the LLVM Team

Warning

These are in-progress notes for the upcoming Extra Clang Tools 23 release. Release notes for previous releases can be found on the Download Page.

Introduction ¶

This document contains the release notes for the Extra Clang Tools, part of the Clang release 23.0.0git. Here we describe the status of the Extra Clang Tools in some detail, including major improvements from the previous release and new feature work. All LLVM releases may be downloaded from the LLVM releases web site.

For more information about Clang or LLVM, including information about the latest release, please see the Clang Web Site or the LLVM Web Site.

Note that if you are reading this file from a Git checkout or the main Clang web page, this document applies to the next release, not the current one. To see the release notes for a specific release, please see the releases page.

Deprecated the clang-tidy check performance-faster-string-find. It has been renamed to performance-prefer-single-char-overloads. The original check will be removed in the 25th release.

Now also provides include files without extension, if they are in a directory only called include.

Improved check_clang_tidy.py script by adding the -check-header argument to simplify testing of header files. This argument automatically manages the creation of temporary header files and ensures that diagnostics and fixes are verified for the specified headers.
Improved clang-tidy -store-check-profile by generating valid JSON when the source file path contains characters that require JSON escaping.

New checks ¶

New bugprone-unsafe-to-allow-exceptions check.

Finds functions where throwing exceptions is unsafe but the function is still marked as potentially throwing.
New llvm-type-switch-case-types check.

Finds llvm::TypeSwitch::Case calls with redundant explicit template arguments that can be inferred from the lambda parameter type.
New llvm-use-vector-utils check.

Finds calls to llvm::to_vector(llvm::map_range(...)) and llvm::to_vector(llvm::make_filter_range(...)) that can be replaced with llvm::map_to_vector and llvm::filter_to_vector.
New modernize-use-std-bit check.

Finds common idioms which can be replaced by standard functions from the <bit> C++20 header.
New modernize-use-string-view check.

Looks for functions returning std::[w|u8|u16|u32]string and suggests to change it to std::[...]string_view for performance reasons if possible.
New modernize-use-structured-binding check.

Finds places where structured bindings could be used to decompose pairs and suggests replacing them.
New performance-string-view-conversions check.

Finds and removes redundant conversions from std::[w|u8|u16|u32]string_view to std::[...]string in call expressions expecting std::[...]string_view.
New performance-use-std-move check.

Suggests insertion of std::move(...) to turn copy assignment operator calls into move assignment ones, when deemed valid and profitable.
New readability-redundant-qualified-alias check.

Finds redundant identity type aliases that re-expose a qualified name and can be replaced with a using declaration.
New readability-trailing-comma check.

Checks for presence or absence of trailing commas in enum definitions and initializer lists.

New check aliases ¶

Renamed hicpp-exception-baseclass to bugprone-std-exception-baseclass. The hicpp-exception-baseclass name is kept as an alias.
Renamed hicpp-ignored-remove-result to bugprone-unused-return-value. The hicpp-ignored-remove-result name is kept as an alias.
Renamed hicpp-no-assembler to portability-no-assembler. The hicpp-no-assembler name is kept as an alias.
Renamed performance-faster-string-find to performance-prefer-single-char-overloads. The performance-faster-string-find name is kept as an alias.

Changes in existing checks ¶

Improved bugprone-argument-comment to also check for C++11 inherited constructors.
Improved bugprone-bad-signal-to-kill-thread check by fixing false negatives when the SIGTERM macro is obtained from a precompiled header.
Improved bugprone-casting-through-void check by running only on C++ files because suggested reinterpret_cast is not available in pure C.
Improved bugprone-derived-method-shadowing-base-method check by correctly ignoring function templates.
Improved bugprone-exception-escape check by adding TreatFunctionsWithoutSpecificationAsThrowing option to support reporting for unannotated functions, enabling reporting when no explicit throw is seen and allowing separate tuning for known and unknown implementations.
Improved bugprone-fold-init-type check by detecting precision loss in overloads with transparent standard functors (e.g. std::plus<>) for std::accumulate, std::reduce, and std::inner_product.
Improved bugprone-inc-dec-in-conditions check by fixing a false positive when increment/decrement operators appear inside lambda bodies that are part of a condition expression.
Improved bugprone-macro-parentheses check by printing the macro definition in the warning message if the macro is defined on command line.
Improved bugprone-pointer-arithmetic-on-polymorphic-object check by fixing a false positive when operator[] is used in a dependent context.
Improved bugprone-std-namespace-modification check by fixing false positives when extending the standard library with a specialization of user-defined type and by removing detection of the compiler generated std namespace extensions.
Improved bugprone-string-constructor check to detect suspicious string constructor calls when the string class constructor has a default allocator argument.
Improved bugprone-unchecked-optional-access to recognize common GoogleTest macros such as ASSERT_TRUE and ASSERT_FALSE, reducing the number of false positives in test code.
Improved bugprone-unsafe-functions check by adding the function std::get_temporary_buffer to the default list of unsafe functions. (This function is unsafe, useless, deprecated in C++17 and removed in C++20).
Improved bugprone-use-after-move check:
- Include the name of the invalidating function in the warning message when a custom invalidation function is used (via the InvalidationFunctions option).
- Add support for annotation of user-defined types as having the same moved-from semantics as standard smart pointers.
Improved cppcoreguidelines-init-variables check by ensuring that member pointers are correctly flagged as uninitialized.
Improved cppcoreguidelines-missing-std-forward check by fixing a false positive for constrained template parameters.
Improved cppcoreguidelines-pro-type-vararg check by no longer warning on builtins with custom type checking (e.g., type-generic builtins like __builtin_clzg) that use variadic declarations as an implementation detail.
Improved cppcoreguidelines-rvalue-reference-param-not-moved check by fixing a false positive on implicitly generated functions such as inherited constructors.
Improved llvm-use-ranges check by adding support for the following algorithms: std::accumulate, std::replace_copy, and std::replace_copy_if.
Improved misc-const-correctness check:
- Added support for analyzing function parameters with the AnalyzeParameters option.
- Fixed false positive where an array of pointers to const was incorrectly diagnosed as allowing the pointee to be made const.
- Fixed false positive where a pointer used with placement new was incorrectly diagnosed as allowing the pointee to be made const.
Improved misc-multiple-inheritance by avoiding false positives when virtual inheritance causes concrete bases to be counted more than once.
Improved misc-throw-by-value-catch-by-reference check:
- Fixed the WarnOnLargeObject option to use the correct name when storing the configuration.
- Fixed the CheckThrowTemporaries option to correctly reflect its configured value in exported settings.
Improved misc-unused-using-decls to not diagnose using declarations as unused if they’re exported from a module.
Improved modernize-pass-by-value check by adding IgnoreMacros option to suppress warnings in macros.
Improved modernize-redundant-void-arg check to work in C23.
Improved modernize-use-equals-delete check by only warning on private deleted functions, if they do not have a public overload or are a special member function.
Improved modernize-use-std-format check:
- Fixed a crash when an argument is part of a macro expansion.
- Added missing #include insertion when the format function call appears as an argument to a macro.
Improved modernize-use-std-print check by adding missing #include insertion when the format function call appears as an argument to a macro.
Improved modernize-use-trailing-return-type check by fixing spurious missing '(' after '__has_feature' errors caused by builtin macros appearing in the return type of a function.
Improved modernize-use-using check by avoiding the generation of invalid code for function types with redundant parentheses.
Improved performance-enum-size check:
- Exclude enum in extern "C" blocks.
- Improved the ignore list to correctly handle typedef and enum.
Improved performance-inefficient-string-concatenation check by adding support for detecting inefficient string concatenation in do-while loops.
Improved performance-inefficient-vector-operation check by correctly handling vector-like classes when push_back/emplace_back are inherited.
Improved performance-move-const-arg check by avoiding false positives on trivially copyable types with a non-public copy constructor.
Improved performance-prefer-single-char-overloads check:
- Now analyzes calls to the starts_with, ends_with, contains, and operator+= string member functions.
- Fixes false negatives when using std::set from libstdc++.
Improved readability-container-size-empty check:
- Fix a crash when a member expression has a non-identifier name.
- Reduce verbosity by removing the note indicating source location of the empty function.
Improved readability-else-after-return check:
- Fixed missed diagnostics when if statements appear in unbraced switch case labels.
- Fixed a false positive involving if statements which contain a return, break, etc., jumped over by a goto.
- Fixed the check potentially breaking code by deleting one too many characters following an else or a curly brace.
- Added support for handling attributed if then-branches such as [[likely]] and [[unlikely]].
- Diagnose and remove redundant else branches after calls to [[noreturn]] functions.
Improved readability-enum-initial-value check: the warning message now uses separate note diagnostics for each uninitialized enumerator, making it easier to see which specific enumerators need explicit initialization.
Improved readability-implicit-bool-conversion check:
- Fixed a false positive where AllowPointerConditions and AllowIntegerConditions options did not suppress warnings when the condition expression involved temporaries (e.g. passing a string literal to a const std::string& parameter).
- Warn and provide fix-its when a macro defined in a system header (e.g. NULL) is implicitly converted to bool.
- Added AllowLogicalOperatorConversion option to suppress warnings on implicit conversions of logical operator results (&&, ||, !) to bool in C.
Improved readability-non-const-parameter check by avoiding false positives on parameters used in dependent expressions (e.g. inside generic lambdas).
Improved readability-redundant-preprocessor check by fixing a false positive for nested #if directives using different builtin expressions such as __has_builtin and __has_cpp_attribute.
Improved readability-simplify-boolean-expr check to provide valid fix suggestions for C23 and later by not using static_cast.
Improved readability-simplify-subscript-expr check by fixing missing warnings when subscripting an object held inside a generic container (e.g. subscripting a std::string held inside a std::vector<std::string>).
Improved readability-suspicious-call-argument check by avoiding a crash from invalid Abbreviations option.

Extra Clang Tools 23.0.0git documentation