| ======================================== |
| Clang 13.0.0 (In-Progress) Release Notes |
| ======================================== |
| |
| .. contents:: |
| :local: |
| :depth: 2 |
| |
| Written by the `LLVM Team <https://llvm.org/>`_ |
| |
| .. warning:: |
| |
| These are in-progress notes for the upcoming Clang 13 release. |
| Release notes for previous releases can be found on |
| `the Download Page <https://releases.llvm.org/download.html>`_. |
| |
| Introduction |
| ============ |
| |
| This document contains the release notes for the Clang C/C++/Objective-C |
| frontend, part of the LLVM Compiler Infrastructure, release 13.0.0. Here we |
| describe the status of Clang in some detail, including major |
| improvements from the previous release and new feature work. For the |
| general LLVM release notes, see `the LLVM |
| documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM |
| releases may be downloaded from the `LLVM releases web |
| site <https://llvm.org/releases/>`_. |
| |
| For more information about Clang or LLVM, including information about the |
| latest release, please see the `Clang Web Site <https://clang.llvm.org>`_ or the |
| `LLVM Web Site <https://llvm.org>`_. |
| |
| 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 <https://llvm.org/releases/>`_. |
| |
| What's New in Clang 13.0.0? |
| =========================== |
| |
| Some of the major new features and improvements to Clang are listed |
| here. Generic improvements to Clang as a whole or to its underlying |
| infrastructure are described first, followed by language-specific |
| sections with improvements to Clang's support for those languages. |
| |
| Major New Features |
| ------------------ |
| |
| - Guaranteed tail calls are now supported with statement attributes |
| ``[[clang::musttail]]`` in C++ and ``__attribute__((musttail))`` in C. The |
| attribute is applied to a return statement (not a function declaration), |
| and an error is emitted if a tail call cannot be guaranteed, for example if |
| the function signatures of caller and callee are not compatible. Guaranteed |
| tail calls enable a class of algorithms that would otherwise use an |
| arbitrary amount of stack space. |
| |
| Improvements to Clang's diagnostics |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| - ... |
| |
| Non-comprehensive list of changes in this release |
| ------------------------------------------------- |
| |
| - The default value of _MSC_VER was raised from 1911 to 1914. MSVC 19.14 has the |
| support to overaligned objects on x86_32 which is required for some LLVM |
| passes. |
| |
| New Compiler Flags |
| ------------------ |
| |
| - ``-Wreserved-identifier`` emits warning when user code uses reserved |
| identifiers. |
| |
| - ``-fstack-usage`` generates an extra .su file per input source file. The .su |
| file contains frame size information for each function defined in the source |
| file. |
| |
| - ``-Wnull-pointer-subtraction`` emits warning when user code may have |
| undefined behaviour due to subtraction involving a null pointer. |
| |
| Deprecated Compiler Flags |
| ------------------------- |
| |
| - ... |
| |
| Modified Compiler Flags |
| ----------------------- |
| |
| - -Wshadow now also checks for shadowed structured bindings |
| - ``-B <prefix>`` (when ``<prefix>`` is a directory) was overloaded to additionally |
| detect GCC installations under ``<prefix>`` (``lib{,32,64}/gcc{,-cross}/$triple``). |
| This behavior was incompatible with GCC, caused interop issues with |
| ``--gcc-toolchain``, and was thus dropped. Specify ``--gcc-toolchain=<dir>`` |
| instead. ``-B``'s other GCC-compatible semantics are preserved: |
| ``$prefix/$triple-$file`` and ``$prefix$file`` are searched for executables, |
| libraries, includes, and data files used by the compiler. |
| - ``-Wextra`` now also implies ``-Wnull-pointer-subtraction.`` |
| |
| Removed Compiler Flags |
| ------------------------- |
| |
| - The clang-cl ``/fallback`` flag, which made clang-cl invoke Microsoft Visual |
| C++ on files it couldn't compile itself, has been removed. |
| |
| - ``-Wreturn-std-move-in-c++11``, which checked whether an entity is affected by |
| `CWG1579 <https://wg21.link/CWG1579>`_ to become implicitly movable, has been |
| removed. |
| |
| New Pragmas in Clang |
| -------------------- |
| |
| - ... |
| |
| Attribute Changes in Clang |
| -------------------------- |
| |
| - ... |
| |
| - Added support for C++11-style ``[[]]`` attributes on using-declarations, as a |
| clang extension. |
| |
| Windows Support |
| --------------- |
| |
| - Fixed reading ``long double`` arguments with ``va_arg`` on x86_64 MinGW |
| targets. |
| |
| C Language Changes in Clang |
| --------------------------- |
| |
| - ... |
| |
| C++ Language Changes in Clang |
| ----------------------------- |
| |
| - The oldest supported GNU libstdc++ is now 4.8.3 (released 2014-05-22). |
| Clang workarounds for bugs in earlier versions have been removed. |
| |
| - ... |
| |
| C++20 Feature Support |
| ^^^^^^^^^^^^^^^^^^^^^ |
| ... |
| |
| C++2b Feature Support |
| ^^^^^^^^^^^^^^^^^^^^^ |
| ... |
| |
| Objective-C Language Changes in Clang |
| ------------------------------------- |
| |
| OpenCL C Language Changes in Clang |
| ---------------------------------- |
| |
| ... |
| |
| ABI Changes in Clang |
| -------------------- |
| |
| OpenMP Support in Clang |
| ----------------------- |
| |
| - Support for loop transformation directives from OpenMP 5.1 have been added. |
| ``#pragma omp unroll`` is a standardized alternative to ``#pragma unroll`` |
| (or ``#pragma clang loop unroll(enable)``) but also allows composition with |
| other OpenMP loop associated constructs as in |
| |
| .. code-block:: c |
| #pragma omp parallel for |
| #pragma omp unroll partial(4) |
| for (int i = 0; i < n; ++i) |
| |
| ``#pragma omp tile`` applies tiling to a perfect loop nest using a |
| user-defined tile size. |
| |
| .. code-block:: c |
| #pragma omp tile sizes(8,8) |
| for (int i = 0; i < m; ++i) |
| for (int j = 0; j < n; ++j) |
| |
| - ... |
| |
| CUDA Support in Clang |
| --------------------- |
| |
| - ... |
| |
| X86 Support in Clang |
| -------------------- |
| |
| - ... |
| |
| Internal API Changes |
| -------------------- |
| |
| These are major API changes that have happened since the 12.0.0 release of |
| Clang. If upgrading an external codebase that uses Clang as a library, |
| this section should help get you past the largest hurdles of upgrading. |
| |
| - ... |
| |
| Build System Changes |
| -------------------- |
| |
| These are major changes to the build system that have happened since the 12.0.0 |
| release of Clang. Users of the build system should adjust accordingly. |
| |
| - The option ``LIBCLANG_INCLUDE_CLANG_TOOLS_EXTRA`` no longer exists. There were |
| two releases with that flag forced off, and no uses were added that forced it |
| on. The recommended replacement is clangd. |
| |
| - ... |
| |
| AST Matchers |
| ------------ |
| |
| - ... |
| |
| clang-format |
| ------------ |
| |
| - Option ``SpacesInLineCommentPrefix`` has been added to control the |
| number of spaces in a line comments prefix. |
| |
| - Option ``SortIncludes`` has been updated from a ``bool`` to an |
| ``enum`` with backwards compatibility. In addition to the previous |
| ``true``/``false`` states (now ``CaseSensitive``/``Never``), a third |
| state has been added (``CaseInsensitive``) which causes an alphabetical sort |
| with case used as a tie-breaker. |
| |
| .. code-block:: c++ |
| |
| // Never (previously false) |
| #include "B/A.h" |
| #include "A/B.h" |
| #include "a/b.h" |
| #include "A/b.h" |
| #include "B/a.h" |
| |
| // CaseSensitive (previously true) |
| #include "A/B.h" |
| #include "A/b.h" |
| #include "B/A.h" |
| #include "B/a.h" |
| #include "a/b.h" |
| |
| // CaseInsensitive |
| #include "A/B.h" |
| #include "A/b.h" |
| #include "a/b.h" |
| #include "B/A.h" |
| #include "B/a.h" |
| |
| - ``BasedOnStyle: InheritParentConfig`` allows to use the ``.clang-format`` of |
| the parent directories to overwrite only parts of it. |
| |
| - Option ``IndentAccessModifiers`` has been added to be able to give access |
| modifiers their own indentation level inside records. |
| |
| - Option ``PPIndentWidth`` has been added to be able to configure pre-processor |
| indentation independent from regular code. |
| |
| - Option ``ShortNamespaceLines`` has been added to give better control |
| over ``FixNamespaceComments`` when determining a namespace length. |
| |
| - Support for Whitesmiths has been improved, with fixes for ``namespace`` blocks |
| and ``case`` blocks and labels. |
| |
| - Option ``EmptyLineAfterAccessModifier`` has been added to remove, force or keep |
| new lines after access modifiers. |
| |
| - Checks for newlines in option ``EmptyLineBeforeAccessModifier`` are now based |
| on the formatted new lines and not on the new lines in the file. (Fixes |
| https://llvm.org/PR41870.) |
| |
| - Option ``SpacesInAngles`` has been improved, it now accepts ``Leave`` value |
| that allows to keep spaces where they are already present. |
| |
| - Option ``AllowShortIfStatementsOnASingleLine`` has been improved, it now |
| accepts ``AllIfsAndElse`` value that allows to put "else if" and "else" short |
| statements on a single line. (Fixes https://llvm.org/PR50019.) |
| |
| - Option ``BreakInheritanceList`` gets a new style, ``AfterComma``. It breaks |
| only after the commas that separate the base-specifiers. |
| |
| - Option ``LambdaBodyIndentation`` has been added to control how the body of a |
| lambda is indented. The default ``Signature`` value indents the body one level |
| relative to whatever indentation the signature has. ``OuterScope`` lets you |
| change that so that the lambda body is indented one level relative to the scope |
| containing the lambda, regardless of where the lambda signature was placed. |
| |
| - Option ``IfMacros`` has been added. This lets you define macros that get |
| formatted like conditionals much like ``ForEachMacros`` get styled like |
| foreach loops. |
| |
| - ``git-clang-format`` no longer formats changes to symbolic links. (Fixes |
| https://llvm.org/PR46992.) |
| |
| - Makes ``PointerAligment: Right`` working with ``AlignConsecutiveDeclarations``. |
| (Fixes https://llvm.org/PR27353) |
| |
| - Option ``AlignArrayOfStructure`` has been added to allow for ordering array-like |
| initializers. |
| |
| - Support for formatting JSON file (\*.json) has been added to clang-format. |
| |
| libclang |
| -------- |
| |
| - ... |
| |
| Static Analyzer |
| --------------- |
| |
| - ... |
| |
| .. _release-notes-ubsan: |
| |
| Undefined Behavior Sanitizer (UBSan) |
| ------------------------------------ |
| |
| Core Analysis Improvements |
| ========================== |
| |
| - ... |
| |
| New Issues Found |
| ================ |
| |
| - ... |
| |
| Python Binding Changes |
| ---------------------- |
| |
| The following methods have been added: |
| |
| - ... |
| |
| Significant Known Problems |
| ========================== |
| |
| Additional Information |
| ====================== |
| |
| A wide variety of additional information is available on the `Clang web |
| page <https://clang.llvm.org/>`_. The web page contains versions of the |
| API documentation which are up-to-date with the Git version of |
| the source code. You can access versions of these documents specific to |
| this release by going into the "``clang/docs/``" directory in the Clang |
| tree. |
| |
| If you have any questions or comments about Clang, please feel free to |
| contact us via the `mailing |
| list <https://lists.llvm.org/mailman/listinfo/cfe-dev>`_. |
