# Extra Clang Tools 21.1.8 documentation

## Extra Clang Tools 21.1.8 Release Notes

Written by the LLVM Team

## Introduction

This document contains the release notes for the Extra Clang Tools, part of the Clang release 21.1.8. 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.

## What’s New in Extra Clang Tools 21.1.8?

Some of the major new features and improvements to Extra Clang Tools are listed here. Generic improvements to Extra Clang Tools as a whole or to its underlying infrastructure are described first, followed by tool-specific sections.

### Major New Features

### Improvements to clangd

#### Language feature support

- Performance improvements and bugfixes to C++20 Modules support

- Improved support for C++23 “deducing this”

- Improvements to objective-c++ support

#### New Language Server Protocol features

- Added support for textDocument/rangesFormatting

- Added support for positionEncoding

#### Compile flags

- Added BuiltinHeaders config key which controls whether clangd’s built-in headers are used or ones extracted from the driver.

#### Hover

- Fixed a bug that would sometimes prevent documentation comments of standard library functions from being shown

#### Code completion

- Added HeaderInsertion config option to control whether code completion inserts a missing header needed for the symbol being completed. This is equivalent to the –header-insertion command-line option.

- Added a CodePatterns config option to control whether code completion should offer code patterns as completions in addition to symbols.

#### Cross-references

- References to symbols are now collected in array designators

- Find-references now works for operators new and delete

- Improvements to code navigation in templated code

#### Call hierarchy

- Call hierarchy now works with the remote index

- Fixed a bug where call hierarchy could sometimes return bogus results

#### Inlay hints

- Parameter hint forwarding now works for variadic forwarding functions declared in header files

- Improved presentation of block-end hints

#### Code actions

- Improved the rename refactor’s name collision checking logic

#### Clang-tidy integration

- Disabled the cppcoreguidelines-macro-to-enum checker which is incompatible with clangd

#### Include-cleaner integration

- Clangd now respects the AngledHeaders and QuotedHeaders config options for headers inserted to resolve include-cleaner diagnostics

#### Miscellaneous

- Various crash fixes and other stability improvements

### Improvements to clang-doc

### Improvements to clang-query

### Improvements to include-cleaner

- Deprecated the `-insert` and `-remove` command line options, and added the `-disable-remove` and `-disable-insert` command line options as replacements. The previous command line options were confusing because they did not imply the default state of the option (which is inserts and removes being enabled). The new options are easier to understand the semantics of.

### Improvements to clang-tidy

- Changed the check_clang_tidy.py tool to use FileCheck’s `--match-full-lines` instead of `strict-whitespace` for `CHECK-FIXES` clauses. Added a `--match-partial-fixes` option to keep previous behavior on specific tests. This may break tests for users with custom out-of-tree checks who use check_clang_tidy.py as-is.

- Improved clang-tidy-diff.py script. Add the -warnings-as-errors argument to treat warnings as errors.

- Improved clang-tidy to show CheckOptions only for checks enabled in Checks when running `--dump-config`.

- Fixed bug in clang-tidy by which HeaderFilterRegex did not take effect when passed via the .clang-tidy file.

- Fixed bug in run_clang_tidy.py where the program would not correctly display the checks enabled by the top-level .clang-tidy file.

#### New checks

- New bugprone-capturing-this-in-member-variable check.

  Finds lambda captures and `bind` function calls that capture the `this` pointer and store it as class members without handle the copy and move constructors and the assignments.

- New bugprone-misleading-setter-of-reference check.

  Finds setter-like member functions that take a pointer parameter and set a reference member of the same class with the pointed value.

- New bugprone-unintended-char-ostream-output check.

  Finds unintended character output from `unsigned char` and `signed char` to an `ostream`.

- New cppcoreguidelines-use-enum-class check.

  Finds unscoped (non-class) `enum` declarations and suggests using `enum class` instead.

- New llvm-prefer-static-over-anonymous-namespace check.

  Finds function and variable declarations inside anonymous namespace and suggests replacing them with `static` declarations.

- New modernize-use-scoped-lock check.

  Finds uses of `std::lock_guard` and suggests replacing them with C++17’s alternative `std::scoped_lock`.

- New portability-avoid-pragma-once check.

  Finds uses of `#pragma once` and suggests replacing them with standard include guards (`#ifndef`/`#define`/`#endif`) for improved portability.

- New readability-ambiguous-smartptr-reset-call check.

  Finds potentially erroneous calls to `reset` method on smart pointers when the pointee type also has a `reset` method.

- New readability-use-concise-preprocessor-directives check.

  Finds uses of `#if` that can be simplified to `#ifdef` or `#ifndef` and, since C23 and C++23, uses of `#elif` that can be simplified to `#elifdef` or `#elifndef`.

#### New check aliases

#### Changes in existing checks

- Improved bugprone-crtp-constructor-accessibility check by fixing false positives on deleted constructors that cannot be used to construct objects, even if they have public or protected access.

- Improved bugprone-exception-escape check to print stack trace of a potentially escaped exception.

- Added an option to bugprone-multi-level-implicit-pointer-conversion to choose whether to enable the check in C code or not.

- Improved bugprone-optional-value-conversion check to detect conversion in argument of `std::make_optional`.

- Improved bugprone-sizeof-expression check by adding WarnOnSizeOfInLoopTermination option to detect misuses of `sizeof` expression in loop conditions.

- Improved bugprone-string-constructor check to find suspicious calls of `std::string` constructor with char pointer, start position and length parameters.

- Improved bugprone-unchecked-optional-access fixing false positives from smart pointer accessors repeated in checking `has_value` and accessing `value`. The option IgnoreSmartPointerDereference should no longer be needed and will be removed. Also fixing false positive from const reference accessors to objects containing optional member.

- Improved bugprone-unsafe-functions check to allow specifying additional C++ member functions to match.

- Improved cert-err33-c check by fixing false positives when a function name is just prefixed with a targeted function name.

- Improved concurrency-mt-unsafe check by fixing a false positive where `strerror` was flagged as MT-unsafe.

- Improved cppcoreguidelines-avoid-goto check by adding the option IgnoreMacros to ignore `goto` labels defined in macros.

- Improved cppcoreguidelines-interfaces-global-init check by fixing false positives on uses of `constinit` variables.

- Improved cppcoreguidelines-missing-std-forward check by adding a flag to specify the function used for forwarding instead of `std::forward`.

- Improved cppcoreguidelines-pro-bounds-pointer-arithmetic check by fixing false positives when calling indexing operators that do not perform pointer arithmetic in template, for example `std::map::operator[]` and when pointer arithmetic was used through type aliases.

- Improved cppcoreguidelines-rvalue-reference-param-not-moved check by adding a flag to specify the function used for moving instead of `std::move`.

- Improved cppcoreguidelines-special-member-functions check by adding the option IgnoreMacros to ignore classes defined in macros.

- Improved google-readability-namespace-comments check by adding the option AllowOmittingNamespaceComments to accept if a namespace comment is omitted entirely.

- Improved hicpp-avoid-goto check by adding the option IgnoreMacros to ignore `goto` labels defined in macros.

- Improved hicpp-special-member-functions check by adding the option IgnoreMacros to ignore classes defined in macros.

- Improved llvm-namespace-comment check by adding the option AllowOmittingNamespaceComments to accept if a namespace comment is omitted entirely.

- Improved misc-const-correctness check by adding the option AllowedTypes, that excludes specified types from const-correctness checking and fixing false positives when modifying variant by `operator[]` with template in parameters and supporting to check pointee mutation by AnalyzePointers option and fixing false positives when using const array type.

- Improved misc-include-cleaner check by adding the options UnusedIncludes and MissingIncludes, which specify whether the check should report unused or missing includes respectively.

- Improved misc-redundant-expression check by providing additional examples and fixing some macro related false positives.

- Improved misc-unconventional-assign-operator check by fixing false positives when copy assignment operator function in a template class returns the result of another assignment to `*this` (`return *this=...`).

- Improved misc-unused-using-decls check by fixing false positives on `operator""` with template parameters.

- Improved misc-use-internal-linkage check by fix false positives for function or variable in header file which contains macro expansion and excluding variables with `thread_local` storage class specifier from being matched.

- Improved modernize-pass-by-value check by fixing false positives when class passed by const-reference had a private move constructor.

- Improved modernize-type-traits check by detecting more type traits.

- Improved modernize-use-default-member-init check by matching arithmetic operations, `constexpr` and `static` values, and detecting explicit casting of built-in types within member list initialization.

- Improved modernize-use-designated-initializers check by avoiding diagnosing designated initializers for `std::array` initializations.

- Improved modernize-use-ranges check by updating suppress warnings logic for `nullptr` in `std::find`.

- Improved modernize-use-starts-ends-with check by adding more matched scenarios of `find` and `rfind` methods and fixing false positives when those methods were called with 3 arguments.

- Improved modernize-use-std-numbers check to support math functions of different precisions.

- Improved modernize-use-trailing-return-type check by adding support to modernize lambda signatures to use trailing return type and adding two new options: TransformFunctions and TransformLambdas to control whether function declarations and lambdas should be transformed by the check. Fixed false positives when lambda was matched as a function in C++11 mode.

- Improved performance-move-const-arg check by fixing false negatives on ternary operators calling `std::move`.

- Improved performance-unnecessary-value-param check performance by tolerating fix-it breaking compilation when functions is used as pointers to avoid matching usage of functions within the current compilation unit. Added an option IgnoreCoroutines with the default value true to suppress this check for coroutines where passing by reference may be unsafe.

- Improved readability-convert-member-functions-to-static check by fixing false positives on member functions with an explicit object parameter.

- Improved readability-function-size check by adding new option CountMemberInitAsStmt that allows counting class member initializers in constructors as statements.

- Improved readability-math-missing-parentheses check by fixing false negatives where math expressions are the operand of assignment operators or comparison operators.

- Improved readability-named-parameter check by adding the option InsertPlainNamesInForwardDecls to insert parameter names without comments for forward declarations only.

- Improved readability-qualified-auto check by adding the option AllowedTypes, that excludes specified types from adding qualifiers.

- Improved readability-redundant-inline-specifier check by fixing false positives on out-of-line explicitly defaulted functions.

- Improved readability-redundant-smartptr-get check by fixing some false positives involving smart pointers to arrays.

#### Removed checks

#### Miscellaneous

### Improvements to include-fixer

The improvements are…

### Improvements to clang-include-fixer

The improvements are…

### Improvements to modularize

The improvements are…

### Improvements to pp-trace

### Clang-tidy Visual Studio plugin