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249 lines
7.4 KiB
249 lines
7.4 KiB
=====================================
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Clang 3.9 (In-Progress) Release Notes
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=====================================
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.. contents::
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:local:
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:depth: 2
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Written by the `LLVM Team <http://llvm.org/>`_
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.. warning::
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These are in-progress notes for the upcoming Clang 3.9 release. You may
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prefer the `Clang 3.8 Release Notes
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<http://llvm.org/releases/3.8.0/tools/clang/docs/ReleaseNotes.html>`_.
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Introduction
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============
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This document contains the release notes for the Clang C/C++/Objective-C
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frontend, part of the LLVM Compiler Infrastructure, release 3.9. Here we
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describe the status of Clang in some detail, including major
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improvements from the previous release and new feature work. For the
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general LLVM release notes, see `the LLVM
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documentation <http://llvm.org/docs/ReleaseNotes.html>`_. All LLVM
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releases may be downloaded from the `LLVM releases web
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site <http://llvm.org/releases/>`_.
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For more information about Clang or LLVM, including information about
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the latest release, please check out the main please see the `Clang Web
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Site <http://clang.llvm.org>`_ or the `LLVM Web
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Site <http://llvm.org>`_.
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Note that if you are reading this file from a Subversion checkout or the
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main Clang web page, this document applies to the *next* release, not
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the current one. To see the release notes for a specific release, please
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see the `releases page <http://llvm.org/releases/>`_.
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What's New in Clang 3.9?
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========================
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Some of the major new features and improvements to Clang are listed
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here. Generic improvements to Clang as a whole or to its underlying
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infrastructure are described first, followed by language-specific
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sections with improvements to Clang's support for those languages.
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Major New Features
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------------------
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- Clang will no longer passes --build-id by default to the linker. In modern
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linkers that is a relatively expensive option. It can be passed explicitly
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with -Wl,--build-id. To have clang always pass it, build clang with
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-DENABLE_LINKER_BUILD_ID.
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Improvements to Clang's diagnostics
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Clang's diagnostics are constantly being improved to catch more issues,
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explain them more clearly, and provide more accurate source information
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about them. The improvements since the 3.7 release include:
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- ...
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New Compiler Flags
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------------------
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The option ....
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New Pragmas in Clang
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-----------------------
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Clang now supports the ...
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Windows Support
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---------------
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Clang's support for building native Windows programs ...
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TLS is enabled for Cygwin defaults to -femulated-tls.
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C Language Changes in Clang
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---------------------------
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The -faltivec and -maltivec flags no longer silently include altivec.h on Power platforms.
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`RenderScript
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<https://developer.android.com/guide/topics/renderscript/compute.html>`_
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support added to the Frontend and enabled by the '-x renderscript' option or
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the '.rs' file extension.
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...
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C11 Feature Support
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^^^^^^^^^^^^^^^^^^^
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...
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C++ Language Changes in Clang
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-----------------------------
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- Clang now enforces the rule that a *using-declaration* cannot name an enumerator of a
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scoped enumeration.
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.. code-block:: c++
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namespace Foo { enum class E { e }; }
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namespace Bar {
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using Foo::E::e; // error
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constexpr auto e = Foo::E::e; // ok
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}
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- Clang now enforces the rule that an enumerator of an unscoped enumeration declared at
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class scope can only be named by a *using-declaration* in a derived class.
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.. code-block:: c++
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class Foo { enum E { e }; }
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using Foo::e; // error
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static constexpr auto e = Foo::e; // ok
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...
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C++1z Feature Support
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^^^^^^^^^^^^^^^^^^^^^
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Clang's experimental support for the upcoming C++1z standard can be enabled with ``-std=c++1z``.
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Changes to C++1z features since Clang 3.8:
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- The ``[[fallthrough]]``, ``[[nodiscard]]``, and ``[[maybe_unused]]`` attributes are
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supported in C++11 onwards, and are largely synonymous with Clang's existing attributes
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``[[clang::fallthrough]]``, ``[[gnu::warn_unused_result]]``, and ``[[gnu::unused]]``.
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Use ``-Wimplicit-fallthrough`` to warn on unannotated fallthrough within ``switch``
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statements.
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- In C++1z mode, aggregate initialization can be performed for classes with base classes:
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.. code-block:: c++
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struct A { int n; };
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struct B : A { int x, y; };
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B b = { 1, 2, 3 }; // b.n == 1, b.x == 2, b.y == 3
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- The range in a range-based ``for`` statement can have different types for its ``begin``
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and ``end`` iterators. This is permitted as an extension in C++11 onwards.
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- Lambda-expressions can explicitly capture ``*this`` (to capture the surrounding object
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by copy). This is permitted as an extension in C++11 onwards.
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- Objects of enumeration type can be direct-list-initialized from a value of the underlying
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type. ``E{n}`` is equivalent to ``E(n)``, except that it implies a check for a narrowing
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conversion.
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- Unary *fold-expression*\s over an empty pack are now rejected for all operators
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other than ``&&``, ``||``, and ``,``.
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...
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Objective-C Language Changes in Clang
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-------------------------------------
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...
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OpenCL C Language Changes in Clang
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----------------------------------
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...
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OpenMP Support in Clang
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----------------------------------
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Added support for all non-offloading features from OpenMP 4.5, including using
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data members in private clauses of non-static member functions. Additionally,
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data members can be used as loop control variables in loop-based directives.
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Currently Clang supports OpenMP 3.1 and all non-offloading features of
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OpenMP 4.0/4.5. Offloading features are under development. Clang defines macro
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_OPENMP and sets it to OpenMP 3.1 (in accordance with OpenMP standard) by
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default. User may change this value using ``-fopenmp-version=[31|40|45]`` option.
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The codegen for OpenMP constructs was significantly improved to produce much
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more stable and faster code.
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Internal API Changes
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--------------------
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These are major API changes that have happened since the 3.8 release of
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Clang. If upgrading an external codebase that uses Clang as a library,
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this section should help get you past the largest hurdles of upgrading.
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- ...
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AST Matchers
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------------
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- has and hasAnyArgument: Matchers no longer ignores parentheses and implicit
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casts on the argument before applying the inner matcher. The fix was done to
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allow for greater control by the user. In all existing checkers that use this
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matcher all instances of code ``hasAnyArgument(<inner matcher>)`` or
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``has(<inner matcher>)`` must be changed to
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``hasAnyArgument(ignoringParenImpCasts(<inner matcher>))`` or
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``has(ignoringParenImpCasts(<inner matcher>))``.
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...
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libclang
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--------
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...
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Static Analyzer
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---------------
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...
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Core Analysis Improvements
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==========================
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- ...
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New Issues Found
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================
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- ...
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Python Binding Changes
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----------------------
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The following methods have been added:
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- ...
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Significant Known Problems
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==========================
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Additional Information
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======================
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A wide variety of additional information is available on the `Clang web
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page <http://clang.llvm.org/>`_. The web page contains versions of the
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API documentation which are up-to-date with the Subversion version of
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the source code. You can access versions of these documents specific to
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this release by going into the "``clang/docs/``" directory in the Clang
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tree.
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If you have any questions or comments about Clang, please feel free to
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contact us via the `mailing
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list <http://lists.llvm.org/mailman/listinfo/cfe-dev>`_.
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