0a6a1f1d05
This brings our tree to NetBSD 7.0, as found on -current on the 10-10-2015. This updates: - LLVM to 3.6.1 - GCC to GCC 5.1 - Replace minix/commands/zdump with usr.bin/zdump - external/bsd/libelf has moved to /external/bsd/elftoolchain/ - Import ctwm - Drop sprintf from libminc Change-Id: I149836ac18e9326be9353958bab9b266efb056f0
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=======================
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Clang 3.6 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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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 3.6. 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/releases/3.6.0/docs/ReleaseNotes.html>`_.
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All LLVM 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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What's New in Clang 3.6?
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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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- The __has_attribute built-in macro no longer queries for attributes across
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multiple attribute syntaxes (GNU, C++11, __declspec, etc). Instead, it only
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queries GNU-style attributes. With the addition of __has_cpp_attribute and
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__has_declspec_attribute, this allows for more precise coverage of attribute
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syntax querying.
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- clang-format now supports formatting Java code.
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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 3.5 release include:
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- Smarter typo correction. Clang now tries a bit harder to give a usable
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suggestion in more cases, and can now successfully recover in more
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situations where the suggestion changes how an expression is parsed.
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New Compiler Flags
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------------------
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The ``-fpic`` option now uses small pic on PowerPC.
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The __EXCEPTIONS macro
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----------------------
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``__EXCEPTIONS`` is now defined when landing pads are emitted, not when
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C++ exceptions are enabled. The two can be different in Objective-C files:
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If C++ exceptions are disabled but Objective-C exceptions are enabled,
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landing pads will be emitted. Clang 3.6 is switching the behavior of
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``__EXCEPTIONS``. Clang 3.5 confusingly changed the behavior of
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``has_feature(cxx_exceptions)``, which used to be set if landing pads were
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emitted, but is now set if C++ exceptions are enabled. So there are 3 cases:
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Clang before 3.5:
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``__EXCEPTIONS`` is set if C++ exceptions are enabled, ``cxx_exceptions``
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enabled if C++ or ObjC exceptions are enabled
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Clang 3.5:
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``__EXCEPTIONS`` is set if C++ exceptions are enabled, ``cxx_exceptions``
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enabled if C++ exceptions are enabled
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Clang 3.6:
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``__EXCEPTIONS`` is set if C++ or ObjC exceptions are enabled,
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``cxx_exceptions`` enabled if C++ exceptions are enabled
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To reliably test if C++ exceptions are enabled, use
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``__EXCEPTIONS && __has_feature(cxx_exceptions)``, else things won't work in
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all versions of Clang in Objective-C++ files.
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New Pragmas in Clang
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-----------------------
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Clang now supports the `#pragma unroll` and `#pragma nounroll` directives to
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specify loop unrolling optimization hints. Placed just prior to the desired
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loop, `#pragma unroll` directs the loop unroller to attempt to fully unroll the
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loop. The pragma may also be specified with a positive integer parameter
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indicating the desired unroll count: `#pragma unroll _value_`. The unroll count
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parameter can be optionally enclosed in parentheses. The directive `#pragma
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nounroll` indicates that the loop should not be unrolled. These unrolling hints
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may also be expressed using the `#pragma clang loop` directive. See the Clang
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`language extensions
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<http://clang.llvm.org/docs/LanguageExtensions.html#extensions-for-loop-hint-optimizations>`_
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for details.
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Windows Support
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---------------
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- Many, many bug fixes.
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- Clang can now self-host using the ``msvc`` environment on x86 and x64
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Windows. This means that Microsoft C++ ABI is more or less feature-complete,
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minus exception support.
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- Added more MSVC compatibility hacks, such as allowing more lookup into
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dependent bases of class templates when there is a known template pattern.
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As a result, applications using Active Template Library (ATL) or Windows
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Runtime Library (WRL) headers should compile correctly.
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- Added support for the Visual C++ ``__super`` keyword.
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- Added support for MSVC's ``__vectorcall`` calling convention, which is used
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in the upcoming Visual Studio 2015 STL.
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- Added basic support for DWARF debug information in COFF files.
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C Language Changes in Clang
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---------------------------
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- The default language mode for C compilations with Clang has been changed from
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C99 with GNU extensions to C11 with GNU extensions. C11 is largely
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backwards-compatible with C99, but if you want to restore the former behavior
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you can do so with the `-std=gnu99` flag.
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C11 Feature Support
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^^^^^^^^^^^^^^^^^^^
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- Clang now provides an implementation of the standard C11 header `<stdatomic.h>`.
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C++ Language Changes in Clang
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-----------------------------
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- An `upcoming change to C++ <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3922.html>_`
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changes the semantics of certain deductions of `auto` from a braced initializer
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list. Following the intent of the C++ committee, this change will be applied to
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our C++11 and C++14 modes as well as our experimental C++17 mode. Clang 3.6
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does not yet implement this change, but to provide a transition period, it
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warns on constructs whose meaning will change. The fix in all cases is to
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add an `=` prior to the left brace.
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- Clang now supports putting identical constructors and destructors in
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the C5/D5 comdat, reducing code duplication.
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- Clang will put individual ``.init_array/.ctors`` sections in
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comdats, reducing code duplication and speeding up startup.
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C++17 Feature Support
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^^^^^^^^^^^^^^^^^^^^^
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Clang has experimental support for some proposed C++1z (tentatively, C++17)
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features. This support can be enabled using the `-std=c++1z` flag.
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New in Clang 3.6 is support for:
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- Fold expressions
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- `u8` character literals
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- Nested namespace definitions: `namespace A::B { ... }` as a shorthand for
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`namespace A { namespace B { ... } }`
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- Attributes for namespaces and enumerators
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- Constant evaluation for all non-type template arguments
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Note that these features may be changed or removed in future Clang releases
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without notice.
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Support for `for (identifier : range)` as a synonym for
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`for (auto &&identifier : range)` has been removed as it is no longer currently
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considered for C++17.
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For more details on C++ feature support, see
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`the C++ status page <http://clang.llvm.org/cxx_status.html>`_.
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OpenMP Language Changes in Clang
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--------------------------------
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Clang 3.6 contains codegen for many individual OpenMP pragmas, but combinations are not completed yet.
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We plan to continue codegen code drop aiming for completion in 3.7. Please see this link for up-to-date
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`status <https://github.com/clang-omp/clang/wiki/Status-of-supported-OpenMP-constructs>_`.
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LLVM's OpenMP runtime library, originally developed by Intel, has been modified to work on ARM, PowerPC,
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as well as X86. The Runtime Library's compatibility with GCC 4.9 is improved
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- missed entry points added, barrier and fork/join code improved, one more type of barrier enabled.
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Support for ppc64le architecture is now available and automatically detected when using cmake system.
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Using makefile the new "ppc64le" arch type is available.
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Contributors to this work include AMD, Argonne National Lab., IBM, Intel, Texas Instruments, University of Houston and many others.
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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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