Improvements to clangd
Performance
clangd’s memory usage is significantly reduced on most Linux systems. In particular, memory usage should not increase dramatically over time.
The standard allocator on most systems is glibc’s ptmalloc2, and it creates disproportionately large heaps when handling clangd’s allocation patterns. By default, clangd will now periodically call malloc_trim to release free pages on glibc systems.
Users of other allocators (such as jemalloc or tcmalloc) on glibc systems can disable this using --malloc_trim=0 or the CMake flag -DCLANGD_MALLOC_TRIM=0.
Added the $/memoryUsage request: an LSP extension. This provides a breakdown of the memory clangd thinks it is using (excluding malloc overhead etc). The clangd VSCode extension supports showing the memory usage tree.
Parsing and selection
Improved navigation of broken code in C using Recovery AST. (This has been enabled for C++ since clangd 11).
Types are understood more often in broken code. (This is the first release where Recovery AST preserves speculated types).
Heuristic resolution for dependent names in templates.
Code completion
Higher priority for symbols that were already used in this file, and symbols from namespaces mentioned in this file. (Estimated 3% accuracy improvement)
Introduced a ranking algorithm trained on snippets from a large C++ codebase. Use the flag --ranking-model=decision_forest to try this (Estimated 6% accuracy improvement). This mode is likely to become the default in future.
Note: this is a generic model, not specialized for your code. clangd does not collect any data from your code to train code completion.
Signature help works with functions with template-dependent parameter types.
Go to definition
Selecting an auto or decltype keyword will attempt to navigate to a definition of the deduced type.
Improved handling of aliases: navigate to the underlying entity more often.
Better understanding of declaration vs definition for Objective-C classes and protocols.
Selecting a pure-virtual method shows its overrides.
Find references
Indexes are smarter about not returning stale references when code is deleted.
References in implementation files are always indexed, so results should be more complete.
Find-references on a virtual method shows references to overridden methods.
New navigation features
Call hierarchy (textDocument/callHierarchy) is supported. Only incoming calls are available.
Go to implementation (textDocument/implementation) is supported on abstract classes, and on virtual methods.
Symbol search (workspace/symbol) queries may be partially qualified. That is, typing b::Foo will match the symbol a:🅱️:c::Foo.
Refactoring
New refactoring: populate switch statement with cases. (This acts as a fix for the -Wswitch-enum warning).
Renaming templates is supported, and many other complex cases were fixed.
Attempting to rename to an invalid or conflicting name can produce an error message rather than broken code. (Not all cases are detected!)
The accuracy of many code actions has been improved.
Hover
Hovers for auto and decltype show the type in the same style as other hovers. this is also now supported.
Displayed type names are more consistent and idiomatic.
Semantic highlighting
Inactive preprocessor regions (#ifdef) are highlighted as comments.
clangd 12 is the last release with support for the non-standard textDocument/semanticHighlights notification. Clients sholud migrate to the textDocument/semanticTokens request added in LSP 3.16.
Remote index (alpha)
clangd can now connect to a remote index server instead of building a project index locally. This saves resources in large codebases that are slow to index.
The server program is clangd-index-server, and it consumes index files produced by clangd-indexer.
This feature requires clangd to be built with the CMake flag -DCLANGD_ENABLE_REMOTE=On, which requires GRPC libraries and is not enabled by default. Unofficial releases of the remote-index-enabled client and server tools are at https://github.com/clangd/clangd/releases
Large projects can deploy a shared server, and check in a .clangd file to enable it (in the Index.External section). We hope to provide such a server for llvm-project itself in the near future.
Configuration
Static and remote indexes can be configured in the Index.External section. Different static indexes can now be used for different files. (Obsoletes the flag --index-file).
Diagnostics can be filtered or suppressed in the Diagnostics section.
Clang-tidy checks can be enabled/disabled in the Diagnostics.ClangTidy section. (Obsoletes the flag --clang-tidy-checks).
The compilation database directory can be configured in the CompileFlags section. Different compilation databases can now be specified for different files. (Obsoletes the flag --compile-commands-dir).
Errors in loaded configuration files are published as LSP diagnostics, and so should be shown in your editor.
Full reference of configuration options
System integration
Changes to compile_commands.json and compile_flags.txt will take effect the next time a file is parsed, without restarting clangd.
clangd --check=<filename> can be run on the command-line to simulate opening a file without actually using an editor. This can be useful to reproduce crashes or aother problems.
Various fixes to handle filenames correctly (and case-insensitively) on windows.
If incoming LSP messages are malformed, the logs now contain details.
Miscellaneous
“Show AST” request (textDocument/ast) added as an LSP extension. This displays a simplified view of the clang AST for selected code. The clangd VSCode extension supports this.
clangd should no longer crash while loading old or corrupt index files.
The flags --index, --recovery-ast and -suggest-missing-includes have been retired. These features are now always enabled.
Too many stability and correctness fixes to mention.
What’s New in Extra Clang Tools 10.0.0?
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
clangd documentation is now found at https://clangd.llvm.org/
Go-to-definition, hover, find-references etc use a new mechanism to identify what is under the cursor, which is (hopefully) more consistent and accurate.
clangd should be able to reliably locate the standard library/SDK on macOS.
Shutdown more cleanly on receiving a signal. In particular temporary PCH files should be cleaned up.
Find references now works on macros.
clangd can be more easily used remotely or in a docker container.
The --path-mappings flag translates between local and remote paths.
Experimental support for renaming across files (behind the --cross-file-rename flag).
Hover now exposes more information, including the type of symbols and the value of constant expressions.
Go to definition now works in dependent code in more cases, by assuming the primary template is used.
Better recovery and reporting when the compile command for a file can’t be fully parsed.
Switch header/source (an extension) now uses index information in addition to filename heuristics, and is much more robust.
Semantic selection (expand/contract selection) is supported.
Semantic highlighting is more robust, highlights more types of tokens, and as an extension provides information about inactive preprocessor regions.
Code completion results now include an extension field score.
This allows clients to incorporate clangd quality signals when re-ranking code completion after client-side fuzzy-matching.
New refactorings: define function out-of-line, define function in-line, extract function, remove using namespace directive, localize Objective-C string.
Bug fixes and performance improvements :-)
Improvements to clang-doc
clang-doc now generates documentation in HTML format.
Improvements to clang-tidy
New checks
New bugprone-bad-signal-to-kill-thread check.
Finds pthread_kill function calls when a thread is terminated by raising SIGTERM signal.
New bugprone-dynamic-static-initializers check.
Finds instances where variables with static storage are initialized dynamically in header files.
New bugprone-infinite-loop check.
Finds obvious infinite loops (loops where the condition variable is not changed at all).
New bugprone-not-null-terminated-result check
Finds function calls where it is possible to cause a not null-terminated result.
New bugprone-signed-char-misuse check.
Finds signed char to integer conversions which might indicate a programming error.
New cert-mem57-cpp check.
Checks if an object of type with extended alignment is allocated by using the default operator new.
New cert-oop58-cpp check.
Finds assignments to the copied object and its direct or indirect members in copy constructors and copy assignment operators.
New cppcoreguidelines-init-variables check.
Checks whether there are local variables that are declared without an initial value.
New darwin-dispatch-once-nonstatic check.
Finds declarations of dispatch_once_t variables without static or global storage.
New google-upgrade-googletest-case check.
Finds uses of deprecated Googletest APIs with names containing case and replaces them with equivalent APIs with suite.
New linuxkernel-must-use-errs check.
Checks Linux kernel code to see if it uses the results from the functions in linux/err.h.
New llvm-prefer-register-over-unsigned check.
Finds historical use of unsigned to hold vregs and physregs and rewrites them to use Register
New objc-missing-hash check.
Finds Objective-C implementations that implement -isEqual: without also appropriately implementing -hash.
New performance-no-automatic-move check.
Finds local variables that cannot be automatically moved due to constness.
New performance-trivially-destructible check.
Finds types that could be made trivially-destructible by removing out-of-line defaulted destructor declarations.
New readability-make-member-function-const check.
Finds non-static member functions that can be made const because the functions don’t use this in a non-const way.
New readability-qualified-auto check.
Adds pointer and const qualifications to auto-typed variables that are deduced to pointers and const pointers.
New readability-redundant-access-specifiers check.
Finds classes, structs, and unions that contain redundant member access specifiers.
New aliases
New alias cert-pos44-c to bugprone-bad-signal-to-kill-thread was added.
New alias llvm-qualified-auto to readability-qualified-auto was added.
Changes in existing checks
Improved bugprone-posix-return check.
Now also checks if any calls to pthread_* functions expect negative return values.
Improved hicpp-signed-bitwise check.
The check now supports the IgnorePositiveIntegerLiterals option.
Improved modernize-avoid-bind check.
The check now supports supports diagnosing and fixing arbitrary callables instead of only simple free functions. The PermissiveParameterList option has also been added to address situations where the existing fix-it logic would sometimes generate code that no longer compiles.
The modernize-use-equals-default fix no longer adds semicolons where they would be redundant.
Improved modernize-use-override check.
The check now supports the AllowOverrideAndFinal option to eliminate conflicts with gcc -Wsuggest-override or gcc -Werror=suggest-override.
The modernize-use-using check now converts typedefs containing struct definitions and multiple comma-separated types.
Improved readability-magic-numbers check.
The check now supports the IgnoreBitFieldsWidths option to suppress the warning for numbers used to specify bit field widths.
The check was updated to eliminate some false positives (such as using class enumeration as non-type template parameters, or the synthetically computed length of a static user string literal.)
Improved readability-redundant-member-init check.
The check now supports the IgnoreBaseInCopyConstructors option to avoid “base class ‘Foo’ should be explicitly initialized in the copy constructor” warnings or errors with gcc -Wextra or gcc -Werror=extra.
The readability-redundant-string-init check now supports a StringNames option enabling its application to custom string classes.
Renamed checks
The ‘objc-avoid-spinlock’ check was renamed to darwin-avoid-spinlock
9.0.0:
Improvements to clangd
* 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.
Improvements to clang-tidy
New OpenMP module.
New abseil-duration-addition check.
New abseil-duration-conversion-cast check.
New abseil-duration-unnecessary-conversion check.
New abseil-time-comparison check.
New abseil-time-subtraction check.
New android-cloexec-pipe check.
New android-cloexec-pipe2 check.
New bugprone-branch-clone check.
New bugprone-posix-return check.
New bugprone-unhandled-self-assignment check.
New fuchsia-default-arguments-calls check.
New fuchsia-default-arguments-declarations check.
New google-objc-avoid-nsobject-new check.
New google-readability-avoid-underscore-in-googletest-name check.
New llvm-prefer-isa-or-dyn-cast-in-conditionals check.
New modernize-use-trailing-return-type check.
New objc-super-self check.
New openmp-exception-escape check.
New openmp-use-default-none check.
New readability-convert-member-functions-to-static check.
New alias cert-oop54-cpp to bugprone-unhandled-self-assignment was added.
New alias cppcoreguidelines-explicit-virtual-functions to modernize-use-override was added.
Added UseAssignment option to cppcoreguidelines-pro-type-member-init
The fuchsia-default-arguments check has been removed.
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.
Improvements to pp-trace
* Added a new option -callbacks to filter preprocessor callbacks. It replaces the -ignore option.
LLVM 8.0.1 is now available! Download it now, or read the release notes.
This release contains bug-fixes for the LLVM 8.0.0 release. This
release is API and ABI compatible with 8.0.0.
Clang Tools 8.0.0:
Improvements to clangd
clangd now adds namespace qualifiers in code completion, for example, if you type “vec”, the list of completions will include “std::vector”.
When a global index is available, clangd will use it to augment the results of “go to definition” and “find references” queries. Global index also enables global code completion, which suggests symbols that are not imported in the current file and automatically inserts the missing #include directives.
clangd stores the symbol index on disk in a new compact binary serialization format. It is 10x more compact than YAML and 40% more compact than gzipped YAML.
clangd has a new efficient symbol index suitable for complex and fuzzy queries and large code bases (e.g., LLVM, Chromium). This index is used for code completion, go to definition, and cross-references. The architecture of the index allows for complex and fuzzy retrieval criteria and sophisticated scoring.
clangd has a new LSP extension that communicates information about activity on clangd’s per-file worker thread. This information can be displayed to users to let them know that the language server is busy with something. For example, in clangd, building the AST blocks many other operations.
clangd has a new LSP extension that allows the client to supply the compilation commands over LSP, instead of finding compile_commands.json on disk.
clangd has a new LSP extension that allows the client to request fixes to be sent together with diagnostics, instead of asynchronously.
clangd has a new LSP extension that allows the client to resolve a symbol in a light-weight manner, without retrieving further information (like definition location, which may require consulting an index).
Improvements to clang-query
A new command line parameter --preload was added to run commands from a file and then start the interactive interpreter.
The command q can was added as an alias for quit to exit the clang-query interpreter.
It is now possible to bind to named values (the result of let expressions).
It is now possible to write comments in clang-query code. This is primarily useful when using script-mode. Comments are all content following the # character on a line.
The new set print-matcher true command now causes clang-query to print the evaluated matcher together with the resulting bindings.
A new output mode detailed-ast was added to clang-query. The existing dump output mode is now a deprecated alias for detailed-ast
Output modes can now be enabled or disabled non-exclusively.
Improvements to clang-tidy
New abseil-duration-comparison check.
Checks for comparisons which should be done in the absl::Duration domain instead of the float of integer domains.
New abseil-duration-division check.
Checks for uses of absl::Duration division that is done in a floating-point context, and recommends the use of a function that returns a floating-point value.
New abseil-duration-factory-float check.
Checks for cases where the floating-point overloads of various absl::Duration factory functions are called when the more-efficient integer versions could be used instead.
New abseil-duration-factory-scale check.
Checks for cases where arguments to absl::Duration factory functions are scaled internally and could be changed to a different factory function.
New abseil-duration-subtraction check.
Checks for cases where subtraction should be performed in the absl::Duration domain.
New abseil-faster-strsplit-delimiter check.
Finds instances of absl::StrSplit() or absl::MaxSplits() where the delimiter is a single character string literal and replaces with a character.
New abseil-no-internal-dependencies check.
Gives a warning if code using Abseil depends on internal details.
New abseil-no-namespace check.
Ensures code does not open namespace absl as that violates Abseil’s compatibility guidelines.
New abseil-redundant-strcat-calls check.
Suggests removal of unnecessary calls to absl::StrCat when the result is being passed to another absl::StrCat or absl::StrAppend.
New abseil-str-cat-append check.
Flags uses of absl::StrCat() to append to a std::string. Suggests absl::StrAppend() should be used instead.
New abseil-upgrade-duration-conversions check.
Finds calls to absl::Duration arithmetic operators and factories whose argument needs an explicit cast to continue compiling after upcoming API changes.
New bugprone-too-small-loop-variable check.
Detects those for loops that have a loop variable with a “too small” type which means this type can’t represent all values which are part of the iteration range.
New cppcoreguidelines-macro-usage check.
Finds macro usage that is considered problematic because better language constructs exist for the task.
New google-objc-function-naming check.
Checks that function names in function declarations comply with the naming conventions described in the Google Objective-C Style Guide.
New misc-non-private-member-variables-in-classes check.
Finds classes that not only contain the data (non-static member variables), but also have logic (non-static member functions), and diagnoses all member variables that have any other scope other than private.
New modernize-avoid-c-arrays check.
Finds C-style array types and recommend to use std::array<> / std::vector<>.
New modernize-concat-nested-namespaces check.
Checks for uses of nested namespaces in the form of namespace a { namespace b { ... }} and offers change to syntax introduced in C++17 standard: namespace a::b { ... }.
New modernize-deprecated-ios-base-aliases check.
Detects usage of the deprecated member types of std::ios_base and replaces those that have a non-deprecated equivalent.
New modernize-use-nodiscard check.
Adds [[nodiscard]] attributes (introduced in C++17) to member functions to highlight at compile time which return values should not be ignored.
New readability-const-return-type check.
Checks for functions with a const-qualified return type and recommends removal of the const keyword.
New readability-isolate-decl check.
Detects local variable declarations declaring more than one variable and tries to refactor the code to one statement per declaration.
New readability-magic-numbers check.
Detects usage of magic numbers, numbers that are used as literals instead of introduced via constants or symbols.
New readability-redundant-preprocessor check.
Finds potentially redundant preprocessor directives.
New readability-uppercase-literal-suffix check.
Detects when the integral literal or floating point literal has non-uppercase suffix, and suggests to make the suffix uppercase. The list of destination suffixes can be optionally provided.
New alias cert-dcl16-c to readability-uppercase-literal-suffix added.
New alias cppcoreguidelines-avoid-c-arrays to modernize-avoid-c-arrays added.
New alias cppcoreguidelines-non-private-member-variables-in-classes to misc-non-private-member-variables-in-classes added.
New alias hicpp-avoid-c-arrays to modernize-avoid-c-arrays added.
New alias hicpp-uppercase-literal-suffix to readability-uppercase-literal-suffix added.
The cppcoreguidelines-narrowing-conversions check now detects more narrowing conversions: - integer to narrower signed integer (this is compiler implementation defined), - integer - floating point narrowing conversions, - floating point - integer narrowing conversions, - constants with narrowing conversions (even in ternary operator).
The objc-property-declaration check now ignores the Acronyms and IncludeDefaultAcronyms options.
The readability-redundant-smartptr-get check does not warn about calls inside macros anymore by default.
The readability-uppercase-literal-suffix check does not warn about literal suffixes inside macros anymore by default.
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