path: root/docs/ReleaseNotes.rst

=======================================
Clang 9.0.0 (In-Progress) Release Notes
=======================================

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Written by the `LLVM Team <https://llvm.org/>`_

.. warning::

   These are in-progress notes for the upcoming Clang 9 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 9.0.0. 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 Subversion 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 9.0.0?
==========================

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
------------------

- ...

Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- ...

Non-comprehensive list of changes in this release
-------------------------------------------------

- The ``__VERSION__`` macro has been updated.
  Previously this macro contained the string '4.2.1 Compatible' to achieve
  compatibility with GCC 4.2.1, but that should no longer be necessary.
  However, to retrieve Clang's version, please favor the one of the macro
  defined in :ref:`clang namespaced version macros <languageextensions-builtin-macros>`.

- ...


New Compiler Flags
------------------

- ...

Deprecated Compiler Flags
-------------------------

The following options are deprecated and ignored. They will be removed in
future versions of Clang.

- ...

Modified Compiler Flags
-----------------------

- ``clang -dumpversion`` now returns the version of Clang itself.

- ...

New Pragmas in Clang
--------------------

- ...

Attribute Changes in Clang
--------------------------

- ...

Windows Support
---------------

- clang-cl now treats non-existent files as possible typos for flags,
  ``clang-cl /diagnostic:caret /c test.cc`` for example now produces
  ``clang: error: no such file or directory: '/diagnostic:caret'; did you mean '/diagnostics:caret'?``

- The ``-print-search-dirs`` option now separates elements with semicolons,
  as is the norm for path lists on Windows

- Improved handling of dllexport in conjunction with explicit template
  instantiations for MinGW, to allow building a shared libc++ for MinGW
  without ``--export-all-symbols`` to override the dllexport attributes


C Language Changes in Clang
---------------------------

- ``__FILE_NAME__`` macro has been added as a Clang specific extension supported
  in all C-family languages. This macro is similar to ``__FILE__`` except it
  will always provide the last path component when possible.

- Initial support for ``asm goto`` statements (a GNU C extension) has been
  added for control flow from inline assembly to labels. The main consumers of
  this construct are the Linux kernel (CONFIG_JUMP_LABEL=y) and glib. There are
  still a few unsupported corner cases in Clang's integrated assembler and
  IfConverter. Please file bugs for any issues you run into.

- ...

C11 Feature Support
^^^^^^^^^^^^^^^^^^^

...

C++ Language Changes in Clang
-----------------------------

- ...

C++1z Feature Support
^^^^^^^^^^^^^^^^^^^^^

...

Objective-C Language Changes in Clang
-------------------------------------

- Fixed encoding of ObjC pointer types that are pointers to typedefs.

.. code-block:: objc

      typedef NSArray<NSObject *> MyArray;

      // clang used to encode this as "^{NSArray=#}" instead of "@".
      const char *s0 = @encode(MyArray *);

OpenCL C Language Changes in Clang
----------------------------------

...

ABI Changes in Clang
--------------------

- ...

OpenMP Support in Clang
-----------------------

- Added emission of the debug information for NVPTX target devices.

CUDA Support in Clang
---------------------

- Added emission of the debug information for the device code.

Internal API Changes
--------------------

These are major API changes that have happened since the 8.0.0 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 8.0.0
release of Clang. Users of the build system should adjust accordingly.

- In 8.0.0 and below, the install-clang-headers target would install clang's
  resource directory headers. This installation is now performed by the
  install-clang-resource-headers target. Users of the old install-clang-headers
  target should switch to the new install-clang-resource-headers target. The
  install-clang-headers target now installs clang's API headers (corresponding
  to its libraries), which is consistent with the install-llvm-headers target.

- In 9.0.0 and later Clang added a new target, clang-cpp, which generates a
  shared library comprised of all the clang component libraries and exporting
  the clang C++ APIs. Additionally the build system gained the new
  "CLANG_LINK_CLANG_DYLIB" option, which defaults Off, and when set to On, will
  force clang (and clang-based tools) to link the clang-cpp library instead of
  statically linking clang's components. This option will reduce the size of
  binary distributions at the expense of compiler performance.

- ...

AST Matchers
------------

- ...

clang-format
------------

- Add language support for clang-formatting C# files.
- Add Microsoft coding style to encapsulate default C# formatting style.
- Added new option `PPDIS_BeforeHash` (in configuration: `BeforeHash`) to
  `IndentPPDirectives` which indents preprocessor directives before the hash.
- Added new option `AlignConsecutiveMacros` to align the C/C++ preprocessor
  macros of consecutive lines.

libclang
--------

- When `CINDEXTEST_INCLUDE_ATTRIBUTED_TYPES` is not provided when making a
  CXType, the equivalent type of the AttributedType is returned instead of the
  modified type if the user does not want attribute sugar. The equivalent type
  represents the minimally-desugared type which the AttributedType is
  canonically equivalent to.


Static Analyzer
---------------

- The UninitializedObject checker is now considered as stable.
  (moved from the 'alpha.cplusplus' to the 'optin.cplusplus' package)

...

.. _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
==========================

Linux Kernel
============

With support for asm goto, the mainline Linux kernel for x86_64 is now buildable
(and bootable) with Clang 9.  Other architectures that don't require
CONFIG_JUMP_LABEL=y such as arm, aarch64, ppc32, ppc64le, (and possibly mips)
have been supported with older releases of Clang (Clang 4 was first used with
aarch64).

The Android and ChromeOS Linux distributions have moved to building their Linux
kernels with Clang, and Google is currently testing Clang built kernels for
their production Linux kernels.

Further, LLD, llvm-objcopy, llvm-ar, llvm-nm, llvm-objdump can all be used to
build a working Linux kernel.

More information about building Linux kernels with Clang can be found:

- `ClangBuiltLinux web page <https://clangbuiltlinux.github.io/>`_.
- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_.
- `Wiki <https://github.com/ClangBuiltLinux/linux/wiki>`_.
- `Mailing List <clang-built-linux@googlegroups.com>`_.
- `Bi-weekly Meeting <https://calendar.google.com/calendar/embed?src=google.com_bbf8m6m4n8nq5p2bfjpele0n5s%40group.calendar.google.com>`_.
- #clangbuiltlinux on Freenode.
- `Clang Meta bug <https://bugs.llvm.org/show_bug.cgi?id=4068>`_.
- `Continuous Integration <https://travis-ci.com/ClangBuiltLinux/continuous-integration>`_.

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 Subversion 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>`_.