Extra Clang Tools 11.0.0 Release Notes

Written by the LLVM Team

Introduction

This document contains the release notes for the Extra Clang Tools, part of the Clang release 11.0.0. 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.

What’s New in Extra Clang Tools 11.0.0?

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.

Improvements to clangd

Performance

• Eliminated long delays after adding/removing includes (“async preambles”)

• Faster indexing

• Less memory used to index headers used by open files (“dynamic index”)

• Many requests are implicitly cancelled rather than queued when the file is edited, preventing a backlog

• Background indexing can be selectively disabled per-path through config

Selecting and targeting

• Improved understanding and selection around broken code (“recovery AST”)

• Operations like “go-to-definition” will target things on the left of the cursor, if there is nothing eligible on the right.

• Arguments to assert()-like macros can be properly selected.

Diagnostics

• When a header is saved, diagnostics for files that use it are updated.

• Calls std::make_unique produce diagnostics for the constructor call. (Template functions in general are not expanded for performance reasons).

• Diagnostics update more quickly for files that build quickly (no 500ms delay)

• Automatic fixes are offered even when they affect macro arguments.

• Warnings from included headers are not shown (but errors still are).

• A handful of high-quality clang-tidy checks are enabled by default:

  • readability-misleading-indentation,

  • readability-deleted-default,

  • bugprone-integer-division,

  • bugprone-sizeof-expression,

  • bugprone-suspicious-missing-comma,

  • bugprone-unused-raii,

  • bugprone-unused-return-value,

  • misc-unused-using-decls,

  • misc-unused-alias-decls,

  • misc-definitions-in-headers

Refactorings

• Rename applies across the project, using the index.

• Accuracy of rename improved in many places.

• New refactoring: add using declaration for qualified name.

• New refactoring: move function definition out-of-line.

Code completion

• Function call parentheses are not inserted if they already exist.

• Completion of #include filenames triggers earlier (after <, ", and /) and is less aggressive about replacing existing text.

• Documentation is reflowed in the same way as on hover.

Go-to-definition

• Dependent names in templates may be heuristically resolved

• Identifiers in comments may be resolved using other occurrences in the file or in the index.

• Go-to-definition on an override or final specifier jumps to the overridden method.

Hover

• Expressions passed as function arguments show parameter name, conversions etc.

• Members now include the access specifier in the displayed declaration.

• Classes and fields show memory layout information (size and offset).

• Somewhat improved understanding of formatting in documentation comments.

• Trivial inline getters/setters are implicitly documented as such.

Highlighting

• The semanticTokens protocol from LSP 3.16 is supported. (Only token types are exposed, no modifiers yet).

• The non-standard textDocument/semanticHighlighting notification is deprecated and will be removed in clangd 12.

• Placing the cursor on a control flow keyword highlights related flow (e.g. break -> for).

Language support

• clangd features now work inside templates on windows. (MSVC-compatible delayed-template-parsing is no longer used).

• Objective-C properties can be targeted and cross-references are indexed.

• Field names in designated initializers (C++20) can be targeted, and code completion works in many cases.

• goto labels: go-to-defintion, cross-references, and rename all work.

• Concepts (C++20): go-to-definition on concept names, and some limited code completion support for concept members.

System integration

• The project index is now written to $PROJECT/.cache/clangd/index. $PROJECT/.clangd is now expected to be a configuration file.

  Old $PROJECT/.clangd directories can safely be deleted.

  We recommend including both .cache/ and .clangd/ (with trailing slash) in .gitignore, for backward-compatibility with earlier releases of clangd.

• For non-project files (those without a compilation database), the index location better reflects OS conventions:

  • %LocalAppData%\clangd\index on Windows

  • $(getconf DARWIN_USER_CACHE_DIR)/clangd/index on Mac

  • $XDG_CACHE_HOME/clangd/index or ~/.cache/clangd/index on others

  Old ~/.clangd/index directories can safely be deleted.

• clangd now reads configuration from .clangd files inside your project, and from a user configuration file in an OS-specific location:

  • %LocalAppData%\clangd\config.yaml on Windows

  • ~/Library/Preferences/clangd/config.yaml on Mac

  • $XDG_CONFIG_HOME/clangd/config.yaml or ~/.config/clangd/config.yaml on others

  See clangd configuration format.

• clangd will search for compilation databases (compile_commands.json) in a build/ subdirectory, as well as in the project root. This follows CMake conventions, avoiding the need for a symlink in many cases.

• Compile flags can be selectively modified per-path, using configuration.

• Improved filtering of unhelpful compile flags (such as those relating to pre-compiled headers).

• Improved detection of standard library headers location.

Miscellaneous

• Background indexing status is reported using LSP 3.15 progress events (window/workDoneProgress/create).

• Infrastructure for gathering internal metrics. (Off by default, set $CLANGD_METRICS to generate a named CSV file).

• Document versions are now tracked, version is reported along with diagnostics.

• Too many stability and correctness fixes to mention.

Improvements to clang-tidy

New module

• New module llvmlibc.

  This module contains checks related to the LLVM-libc coding standards.

New checks

• New abseil-string-find-str-contains check.

  Finds s.find(...) == string::npos comparisons (for various string-like types) and suggests replacing with absl::StrContains().

• New bugprone-misplaced-pointer-arithmetic-in-alloc check.

  Finds cases where an integer expression is added to or subtracted from the result of a memory allocation function (malloc(), calloc(), realloc(), alloca()) instead of its argument.

• New bugprone-no-escape check.

  Finds pointers with the noescape attribute that are captured by an asynchronously-executed block.

• New bugprone-reserved-identifier check.

  Checks for usages of identifiers reserved for use by the implementation.

• New bugprone-spuriously-wake-up-functions check.

  Finds cnd_wait, cnd_timedwait, wait, wait_for, or wait_until function calls when the function is not invoked from a loop that checks whether a condition predicate holds or the function has a condition parameter.

• New bugprone-suspicious-include check.

  Finds cases where an include refers to what appears to be an implementation file, which often leads to hard-to-track-down ODR violations, and diagnoses them.

• New cert-oop57-cpp check.

  Flags use of the C standard library functions memset, memcpy and memcmp and similar derivatives on non-trivial types.

• New cppcoreguidelines-avoid-non-const-global-variables check.

  Finds non-const global variables as described in check I.2 of C++ Core Guidelines.

• New llvmlibc-callee-namespace check.

  Checks all calls resolve to functions within __llvm_libc namespace.

• New llvmlibc-implementation-in-namespace check.

  Checks all llvm-libc implementation is within the correct namespace.

• New llvmlibc-restrict-system-libc-headers check.

  Finds includes of system libc headers not provided by the compiler within llvm-libc implementations.

• New misc-no-recursion check.

  Finds recursive functions and diagnoses them.

• New modernize-replace-disallow-copy-and-assign-macro check.

  Finds macro expansions of DISALLOW_COPY_AND_ASSIGN and replaces them with a deleted copy constructor and a deleted assignment operator.

• New objc-dealloc-in-category check.

  Finds implementations of -dealloc in Objective-C categories.

• New objc-nsinvocation-argument-lifetime check.

  Finds calls to NSInvocation methods under ARC that don’t have proper argument object lifetimes.

• New readability-use-anyofallof check.

  Finds range-based for loops that can be replaced by a call to std::any_of or std::all_of.

New check aliases

• New alias cert-con36-c to bugprone-spuriously-wake-up-functions was added.

• New alias cert-con54-cpp to bugprone-spuriously-wake-up-functions was added.

• New alias cert-dcl37-c to bugprone-reserved-identifier was added.

• New alias cert-dcl51-cpp to bugprone-reserved-identifier was added.

• New alias cert-str34-c to bugprone-signed-char-misuse was added.

• New alias llvm-else-after-return to readability-else-after-return was added.

Changes in existing checks

• Improved performance-faster-string-find check.

  Now checks std::basic_string_view by default.

• Improved readability-else-after-return check now supports a WarnOnConditionVariables option to control whether to refactor condition variables where possible.

• Improved readability-identifier-naming check.

  Now able to rename member references in class template definitions with explicit access.

• Improved readability-redundant-string-init check now supports a StringNames option enabling its application to custom string classes. The check now detects in class initializers and constructor initializers which are deemed to be redundant.

• Checks supporting the HeaderFileExtensions flag now support ; as a delimiter in addition to ,, with the latter being deprecated as of this release. This simplifies how one specifies the options on the command line: --config="{CheckOptions: [{ key: HeaderFileExtensions, value: h;;hpp;hxx }]}"

• Improved readability-qualified-auto check now supports a AddConstToQualified to enable adding const qualifiers to variables typed with auto * and auto &.

Renamed checks

• The ‘fuchsia-restrict-system-headers’ check was renamed to portability-restrict-system-includes

Other improvements

• For run-clang-tidy.py add option to use alpha checkers from clang-analyzer.