Extra Clang Tools 3.9 Release Notes — Extra Clang Tools 3.9 documentation

# Extra Clang Tools 3.9 documentation

## Extra Clang Tools 3.9 Release Notes

- Introduction
- What’s New in Extra Clang Tools 3.9?
  - Major New Features
  - Improvements to clang-tidy
    - Clang-tidy changes from 3.7 to 3.8

Written by the LLVM Team

## Introduction

This document contains the release notes for the Extra Clang Tools, part of the Clang release 3.9. Here we describe the status of the Extra Clang Tools in some detail, including major improvements from the previous release and new feature work. For the general Clang release notes, see the Clang documentation. 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.

## What’s New in Extra Clang Tools 3.9?

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

- clang-include-fixer, a tool that provides an automated way of adding `#include` directives for missing symbols in one translation unit.

  It aims to provide automated insertion of missing `#includes` with a single button press in an editor. Integration with Vim and a tool to generate the symbol index used by the tool are also part of this release. See the include-fixer documentation for more information.

### Improvements to clang-tidy

clang-tidy‘s checks are constantly being improved to catch more issues, explain them more clearly, and provide more accurate fix-its for the issues identified. The improvements since the 3.8 release include:

- New Boost module containing checks for issues with Boost library.

- New boost-use-to-string check

  Finds usages of `boost::lexical_cast<std::string>` and changes it to `std::to_string`.

- New cert-env33-c check

  Flags calls to `system()`, `popen()`, and `_popen()`, which execute a command processor.

- New cert-err34-c check

  Flags calls to string-to-number conversion functions that do not verify the validity of the conversion.

- New cert-flp30-c check

  Flags `for` loops where the induction expression has a floating-point type.

- New cppcoreguidelines-interfaces-global-init check

  Flags initializers of globals that access extern objects, and therefore can lead to order-of-initialization problems.

- New cppcoreguidelines-pro-type-member-init check

  Flags user-defined constructor definitions that do not initialize all builtin and pointer fields which leaves their memory in an undefined state.

- New google-default-arguments check

  Flags default arguments in virtual methods.

- New misc-dangling-handle check

  Detects dangling references in value handlers like `std::experimental::string_view`.

- New misc-fold-init-type check

  The check flags type mismatches in folds like `std::accumulate` that might result in loss of precision.

- New misc-forward-declaration-namespace check

  Checks if an unused forward declaration is in a wrong namespace.

- New misc-misplaced-const check

  Checks if a `const` qualifier is applied to a `typedef` to pointer type instead of the underlying pointee type.

- New misc-misplaced-widening-cast check

  Warns when there is a explicit redundant cast of a calculation result to a bigger type.

- New misc-multiple-statement-macro check

  Detect multiple statement macros that are used in unbraced conditionals.

- New misc-pointer-and-integral-operation check

  Warns about suspicious operations involving pointers and integral types.

- New misc-redundant-expression check

  Warns about redundant and equivalent expressions.

- New misc-sizeof-expression check

  Warns about incorrect uses of `sizeof` operator.

- New misc-string-constructor check

  Finds string constructors that are suspicious and probably errors.

- New misc-string-literal-with-embedded-nul check

  Warns about suspicious NUL character in string literals which may lead to truncation or invalid character escaping.

- New misc-suspicious-missing-comma check

  Warns about ‘probably’ missing comma in string literals initializer list.

- New misc-suspicious-semicolon check

  Finds most instances of stray semicolons that unexpectedly alter the meaning of the code.

- New misc-suspicious-string-compare check

  Find suspicious usage of runtime string comparison functions.

- New misc-unconventional-assign-operator check replacing the misc-assign-operator-signature check.

  Does not only checks for correct signature but also for correct `return` statements (returning `*this`)

- New misc-unused-using-decls check

  Finds unused `using` declarations.

- New modernize-avoid-bind check

  Finds uses of `std::bind` and replaces simple uses with lambdas.

- New modernize-deprecated-headers check

  Replaces C standard library headers with their C++ alternatives.

- New modernize-make-shared check

  Replaces creation of `std::shared_ptr` from new expression with call to `std::make_shared`.

- New modernize-raw-string-literal check

  Selectively replaces string literals containing escaped characters with raw string literals.

- New modernize-use-bool-literals check

  Finds integer literals which are cast to `bool`.

- New modernize-use-emplace check

  Finds calls that could be changed to emplace.

- New modernize-use-using check

  Finds typedefs and replaces it with usings.

- New performance-faster-string-find check

  Optimize calls to `std::string::find()` and friends when the needle passed is a single character string literal.

- New performance-implicit-cast-in-loop check

  Warns about range-based loop with a loop variable of const ref type where the type of the variable does not match the one returned by the iterator.

- New performance-unnecessary-value-param check

  Flags value parameter declarations of expensive to copy types that are copied for each invocation but it would suffice to pass them by const reference.

- New readability-avoid-const-params-in-decls check

  Warns about top-level const parameters in function declarations.

- New readability-deleted-default check

  Warns about defaulted constructors and assignment operators that are actually deleted.

- Updated readability-identifier-naming-check

  Added support for enforcing the case of macro statements.

- New readability-redundant-control-flow check

  Looks for procedures (functions returning no value) with `return` statements at the end of the function. Such return statements are redundant.

- New readability-redundant-string-init check

  Finds unnecessary string initializations.

- New readability-static-definition-in-anonymous-namespace check

  Finds static function and variable definitions in anonymous namespace.

Fixed bugs:

- Crash when running on compile database with relative source files paths.
- Crash when running with the -fdelayed-template-parsing flag.
- The modernize-use-override check: incorrect fix-its placement around `__declspec` and other attributes.

#### Clang-tidy changes from 3.7 to 3.8

The 3.8 release didn’t include release notes for clang-tidy. In the 3.8 release many new checks have been added to clang-tidy:

- Checks enforcing certain rules of the CERT Secure Coding Standards:

  - cert-dcl03-c (an alias to the pre-existing check misc-static-assert)
  - cert-dcl50-cpp
  - cert-err52-cpp
  - cert-err58-cpp
  - cert-err60-cpp
  - cert-err61-cpp
  - cert-fio38-c (an alias to the pre-existing check misc-non-copyable-objects)
  - cert-oop11-cpp (an alias to the pre-existing check misc-move-constructor-init)

- Checks supporting the C++ Core Guidelines:

  - cppcoreguidelines-pro-bounds-array-to-pointer-decay
  - cppcoreguidelines-pro-bounds-constant-array-index
  - cppcoreguidelines-pro-bounds-pointer-arithmetic
  - cppcoreguidelines-pro-type-const-cast
  - cppcoreguidelines-pro-type-cstyle-cast
  - cppcoreguidelines-pro-type-reinterpret-cast
  - cppcoreguidelines-pro-type-static-cast-downcast
  - cppcoreguidelines-pro-type-union-access
  - cppcoreguidelines-pro-type-vararg

- The functionality of the clang-modernize tool has been moved to the new `modernize` module in clang-tidy along with a few new checks:

  - modernize-loop-convert
  - modernize-make-unique
  - modernize-pass-by-value
  - modernize-redundant-void-arg
  - modernize-replace-auto-ptr
  - modernize-shrink-to-fit (renamed from `readability-shrink-to-fit`)
  - modernize-use-auto
  - modernize-use-default
  - modernize-use-nullptr
  - modernize-use-override (renamed from `misc-use-override`)

- New checks flagging various readability-related issues:

  - readability-identifier-naming
  - readability-implicit-bool-cast
  - readability-inconsistent-declaration-parameter-name
  - readability-uniqueptr-delete-release

- Updated `cppcoreguidelines-pro-member-type-member-init` check

  This check now conforms to C++ Core Guidelines rule Type.6: Always Initialize a Member Variable. The check examines every record type where construction might result in an undefined memory state. These record types needing initialization have at least one default-initialized built-in, pointer, array or record type matching these criteria or a default-initialized direct base class of this kind.

  The check has two complementary aspects:

  1. Ensure every constructor for a record type needing initialization value-initializes all members and direct bases via a combination of in-class initializers and the member initializer list.
  2. Value-initialize every non-member instance of a record type needing initialization that lacks a user-provided default constructor, e.g. a POD.