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=====================================
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Clang 3.4 (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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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 3.4. 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 3.4?
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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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Last release which will build as C++98
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--------------------------------------
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This is expected to be the last release of Clang which compiles using a C++98
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toolchain. We expect to start using some C++11 features in Clang starting after
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this release. That said, we are committed to supporting a reasonable set of
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modern C++ toolchains as the host compiler on all of the platforms. This will
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at least include Visual Studio 2012 on Windows, and Clang 3.1 or GCC 4.7.x on
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Mac and Linux. The final set of compilers (and the C++11 features they support)
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is not set in stone, but we wanted users of Clang to have a heads up that the
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next release will involve a substantial change in the host toolchain
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requirements.
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Note that this change is part of a change for the entire LLVM project, not just
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Clang.
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Major New Features
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------------------
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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 3.3 release include:
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- ...
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New Compiler Flags
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------------------
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- Clang no longer special cases -O4 to enable lto. Explicitly pass -flto to
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enable it.
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- Clang no longer fails on >= -O5. Uses -O3 instead.
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- Command line "clang -O3 -flto a.c -c" and "clang -emit-llvm a.c -c"
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are no longer equivalent.
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- Clang now errors on unknown -m flags (``-munknown-to-clang``),
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unknown -f flags (``-funknown-to-clang``) and unknown
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options (``-what-is-this``).
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C Language Changes in Clang
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---------------------------
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- Added new checked arithmetic builtins for security critical applications.
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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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- Fixed an ABI regression, introduced in Clang 3.2, which affected
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member offsets for classes inheriting from certain classes with tail padding.
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See PR16537.
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- ...
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C++11 Feature Support
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^^^^^^^^^^^^^^^^^^^^^
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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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- OpenCL C "long" now always has a size of 64 bit, and all OpenCL C
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types are aligned as specified in the OpenCL C standard. Also,
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"char" is now always signed.
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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 3.3 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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Wide Character Types
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^^^^^^^^^^^^^^^^^^^^
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The ASTContext class now keeps track of two different types for wide character
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types: WCharTy and WideCharTy. WCharTy represents the built-in wchar_t type
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available in C++. WideCharTy is the type used for wide character literals; in
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C++ it is the same as WCharTy, but in C99, where wchar_t is a typedef, it is an
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integer type.
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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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The static analyzer (which contains additional code checking beyond compiler
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warnings) has improved significantly in both in the core analysis engine and
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also in the kinds of issues it can find.
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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.cs.uiuc.edu/mailman/listinfo/cfe-dev>`_.
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