Background indexing is on by default

When using clangd, it will build an index of your code base (all files listed in your compile database). This index enables go-to-definition, find-references, and even code completion to find symbols across your project.

This feature can consume a lot of CPU. It can be disabled using the --background-index=false flag, and respects -j to use fewer threads. The index is written to .clangd/index in the project root.

Contextual code actions

Extract variable, expand auto, expand macro, convert string to raw string. More to come in the future!

Clang-tidy warnings are available

These will be produced for projects that have a .clang-tidy file in their source tree, as described in the clang-tidy documentation.

Improved diagnostics

Errors from headers are now shown (on the #including line). The message now indicates if fixes are available. Navigation between errors and associated notes is improved (for editors that support Diagnostic.relatedInformation).

Suggested includes

When a class or other name is not found, clangd may suggest to fix this by adding the corresponding #include directive.

Semantic highlighting

clangd can push syntax information to the editor, allowing it to highlight e.g. member variables differently from locals. (requires editor support)

This implements the proposed protocol from https://github.com/microsoft/vscode-languageserver-node/pull/367

Type hierachy

Navigation to base/derived types is possible in editors that support the proposed protocol from https://github.com/microsoft/vscode-languageserver-node/pull/426

Improvements to include insertion

Only headers with #include-guards will be inserted, and the feature can be disabled with the --header-insertion=never flag.

Standard library headers should now be inserted more accurately, particularly for C++ other than libstdc++, and for the C standard library.

Code completion

Overloads are bundled into a single completion item by default. (for editors that support signature-help).

Redundant const/non-const overloads are no longer shown.

Before clangd is warmed up (during preamble build), limited identifier- and index-based code completion is available.

Format-on-type

A new implementation of format-on-type is triggered by hitting enter: it attempts to reformat the previous line and reindent the new line. (Requires editor support).

Toolchain header detection

Projects that use an embedded gcc toolchain may only work when used with the corresponding standard library. clangd can now query the toolchain to find these headers. The compilation database must correctly specify this toolchain, and the --query-driver=/path/to/toolchain/bin/* flag must be passed to clangd.

Miscellaneous improvements

Hover now produces richer Markdown-formatted text (for supported editors).

Rename is safer and more helpful, though is still within one file only.

Files without extensions (e.g. C++ standard library) are handled better.

clangd can understand offsets in UTF-8 or UTF-32 through command-line flags or protocol extensions. (Useful with editors/platforms that don’t speak UTF-16).

Editors that support edits near the cursor in code-completion can set the textDocument.completion.editsNearCursor capability to true, and clangd will provide completions that correct . to ->, and vice-versa.

New OpenMP module.

For checks specific to OpenMP API.

New abseil-duration-addition check.

Checks for cases where addition should be performed in the absl::Time domain.

New abseil-duration-conversion-cast check.

Checks for casts of absl::Duration conversion functions, and recommends the right conversion function instead.

New abseil-duration-unnecessary-conversion check.

Finds and fixes cases where absl::Duration values are being converted to numeric types and back again.

New abseil-time-comparison check.

Prefer comparisons in the absl::Time domain instead of the integer domain.

New abseil-time-subtraction check.

Finds and fixes absl::Time subtraction expressions to do subtraction in the Time domain instead of the numeric domain.

New android-cloexec-pipe check.

This check detects usage of pipe().

New android-cloexec-pipe2 check.

This checks ensures that pipe2() is called with the O_CLOEXEC flag.

New bugprone-branch-clone check.

Checks for repeated branches in if/else if/else chains, consecutive repeated branches in switch statements and indentical true and false branches in conditional operators.

New bugprone-posix-return check.

Checks if any calls to POSIX functions (except posix_openpt) expect negative return values.

New bugprone-unhandled-self-assignment check.

Finds user-defined copy assignment operators which do not protect the code against self-assignment either by checking self-assignment explicitly or using the copy-and-swap or the copy-and-move method.

New fuchsia-default-arguments-calls check.

Warns if a function or method is called with default arguments. This was previously done by fuchsia-default-arguments check, which has been removed.

New fuchsia-default-arguments-declarations check.

Warns if a function or method is declared with default parameters. This was previously done by fuchsia-default-arguments check check, which has been removed.

New google-objc-avoid-nsobject-new check.

Checks for calls to +new or overrides of it, which are prohibited by the Google Objective-C style guide.

New google-readability-avoid-underscore-in-googletest-name check.

Checks whether there are underscores in googletest test and test case names in test macros, which is prohibited by the Googletest FAQ.

New llvm-prefer-isa-or-dyn-cast-in-conditionals check.

Looks at conditionals and finds and replaces cases of cast<>, which will assert rather than return a null pointer, and dyn_cast<> where the return value is not captured. Additionally, finds and replaces cases that match the pattern var && isa<X>(var), where var is evaluated twice.

New modernize-use-trailing-return-type check.

Rewrites function signatures to use a trailing return type.

New objc-super-self check.

Finds invocations of -self on super instances in initializers of subclasses of NSObject and recommends calling a superclass initializer instead.

New openmp-exception-escape check.

Analyzes OpenMP Structured Blocks and checks that no exception escapes out of the Structured Block it was thrown in.

New openmp-use-default-none check.

Finds OpenMP directives that are allowed to contain a default clause, but either don’t specify it or the clause is specified but with the kind other than none, and suggests to use the default(none) clause.

New readability-convert-member-functions-to-static check.

Finds non-static member functions that can be made static.

New alias cert-oop54-cpp to bugprone-unhandled-self-assignment was added.

New alias cppcoreguidelines-explicit-virtual-functions to modernize-use-override was added.

The bugprone-argument-comment now supports CommentBoolLiterals, CommentIntegerLiterals, CommentFloatLiterals, CommentUserDefiniedLiterals, CommentStringLiterals, CommentCharacterLiterals & CommentNullPtrs options.

The bugprone-too-small-loop-variable now supports MagnitudeBitsUpperLimit option. The default value was set to 16, which greatly reduces warnings related to loops which are unlikely to cause an actual functional bug.

Added UseAssignment option to cppcoreguidelines-pro-type-member-init

If set to true, the check will provide fix-its with literal initializers (int i = 0;) instead of curly braces (int i{};).

The fuchsia-default-arguments check has been removed.

Warnings of function or method calls and declarations with default arguments were moved to fuchsia-default-arguments-calls and fuchsia-default-arguments-declarations checks respectively.

The google-runtime-int check has been disabled in Objective-C++.

The modernize-use-override now supports OverrideSpelling and FinalSpelling options.

The misc-throw-by-value-catch-by-reference now supports WarnOnLargeObject and MaxSize options to warn on any large trivial object caught by value.

The Acronyms and IncludeDefaultAcronyms options for the objc-property-declaration check have been removed.