| ======================================= |
| Clang 7.0.0 (In-Progress) Release Notes |
| ======================================= |
| |
| .. contents:: |
| :local: |
| :depth: 2 |
| |
| Written by the `LLVM Team <http://llvm.org/>`_ |
| |
| .. warning:: |
| |
| These are in-progress notes for the upcoming Clang 7 release. |
| Release notes for previous releases can be found on |
| `the Download Page <http://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 7.0.0. 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 <http://llvm.org/docs/ReleaseNotes.html>`_. All LLVM |
| releases may be downloaded from the `LLVM releases web |
| site <http://llvm.org/releases/>`_. |
| |
| For more information about Clang or LLVM, including information about the |
| latest release, please see the `Clang Web Site <http://clang.llvm.org>`_ or the |
| `LLVM Web Site <http://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 <http://llvm.org/releases/>`_. |
| |
| What's New in Clang 7.0.0? |
| ========================== |
| |
| 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 |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| - ``-Wc++98-compat-extra-semi`` is a new flag, which was previously inseparable |
| from ``-Wc++98-compat-pedantic``. The latter still controls the new flag. |
| |
| - ``-Wextra-semi`` now also controls ``-Wc++98-compat-extra-semi``. |
| Please do note that if you pass ``-Wno-c++98-compat-pedantic``, it implies |
| ``-Wno-c++98-compat-extra-semi``, so if you want that diagnostic, you need |
| to explicitly re-enable it (e.g. by appending ``-Wextra-semi``). |
| |
| - ``-Wself-assign`` and ``-Wself-assign-field`` were extended to diagnose |
| self-assignment operations using overloaded operators (i.e. classes). |
| If you are doing such an assignment intentionally, e.g. in a unit test for |
| a data structure, the first warning can be disabled by passing |
| ``-Wno-self-assign-overloaded``, also the warning can be suppressed by adding |
| ``*&`` to the right-hand side or casting it to the appropriate reference type. |
| |
| Non-comprehensive list of changes in this release |
| ------------------------------------------------- |
| |
| - Clang binary and libraries have been renamed from 7.0 to 7. |
| For example, the ``clang`` binary will be called ``clang-7`` |
| instead of ``clang-7.0``. |
| |
| - Clang implements a collection of recent fixes to the C++ standard's definition |
| of "standard-layout". In particular, a class is only considered to be |
| standard-layout if all base classes and the first data member (or bit-field) |
| can be laid out at offset zero. |
| |
| - Clang's handling of the GCC ``packed`` class attribute in C++ has been fixed |
| to apply only to non-static data members and not to base classes. This fixes |
| an ABI difference between Clang and GCC, but creates an ABI difference between |
| Clang 7 and earlier versions. The old behavior can be restored by setting |
| ``-fclang-abi-compat`` to ``6`` or earlier. |
| |
| - Clang implements the proposed resolution of LWG issue 2358, along with the |
| `corresponding change to the Itanium C++ ABI |
| <https://github.com/itanium-cxx-abi/cxx-abi/pull/51>`_, which make classes |
| containing only unnamed non-zero-length bit-fields be considered non-empty. |
| This is an ABI break compared to prior Clang releases, but makes Clang |
| generate code that is ABI-compatible with other compilers. The old |
| behavior can be restored by setting ``-fclang-abi-compat`` to ``6`` or |
| lower. |
| |
| - An existing tool named ``diagtool`` has been added to the release. As the |
| name suggests, it helps with dealing with diagnostics in ``clang``, such as |
| finding out the warning hierarchy, and which of them are enabled by default |
| or for a particular compiler invocation. |
| |
| - ... |
| |
| New Compiler Flags |
| ------------------ |
| |
| - :option:`-fstrict-float-cast-overflow` and |
| :option:`-fno-strict-float-cast-overflow`. |
| |
| When a floating-point value is not representable in a destination integer |
| type, the code has undefined behavior according to the language standard. By |
| default, Clang will not guarantee any particular result in that case. With the |
| 'no-strict' option, Clang attempts to match the overflowing behavior of the |
| target's native float-to-int conversion instructions. |
| |
| - :option: `-fforce-emit-vtables` and `-fno-force-emit-vtables`. |
| |
| In order to improve devirtualization, forces emitting of vtables even in |
| modules where it isn't necessary. It causes more inline virtual functions |
| to be emitted. |
| |
| - ... |
| |
| Deprecated Compiler Flags |
| ------------------------- |
| |
| The following options are deprecated and ignored. They will be removed in |
| future versions of Clang. |
| |
| - ... |
| |
| Modified Compiler Flags |
| ----------------------- |
| |
| - Before Clang 7, we prepended the `#` character to the `--autocomplete` |
| argument to enable cc1 flags. For example, when the `-cc1` or `-Xclang` flag |
| is in the :program:`clang` invocation, the shell executed |
| `clang --autocomplete=#-<flag to be completed>`. Clang 7 now requires the |
| whole invocation including all flags to be passed to the `--autocomplete` like |
| this: `clang --autocomplete=-cc1,-xc++,-fsyn`. |
| |
| New Pragmas in Clang |
| -------------------- |
| |
| Clang now supports the ... |
| |
| |
| Attribute Changes in Clang |
| -------------------------- |
| |
| - Clang now supports function multiversioning with attribute 'target' on ELF |
| based x86/x86-64 environments by using indirect functions. This implementation |
| has a few minor limitations over the GCC implementation for the sake of AST |
| sanity, however it is otherwise compatible with existing code using this |
| feature for GCC. Consult the documentation for the target attribute for more |
| information. |
| |
| - ... |
| |
| Windows Support |
| --------------- |
| |
| Clang's support for building native Windows programs ... |
| |
| |
| C Language Changes in Clang |
| --------------------------- |
| |
| - ... |
| |
| ... |
| |
| C11 Feature Support |
| ^^^^^^^^^^^^^^^^^^^ |
| |
| ... |
| |
| C++ Language Changes in Clang |
| ----------------------------- |
| |
| - ... |
| |
| C++1z Feature Support |
| ^^^^^^^^^^^^^^^^^^^^^ |
| |
| ... |
| |
| Objective-C Language Changes in Clang |
| ------------------------------------- |
| |
| ... |
| |
| OpenCL C Language Changes in Clang |
| ---------------------------------- |
| |
| ... |
| |
| OpenMP Support in Clang |
| ---------------------------------- |
| |
| - ... |
| |
| CUDA Support in Clang |
| --------------------- |
| |
| - Clang will now try to locate the CUDA installation next to :program:`ptxas` |
| in the `PATH` environment variable. This behavior can be turned off by passing |
| the new flag `--cuda-path-ignore-env`. |
| |
| - Clang now supports generating object files with relocatable device code. This |
| feature needs to be enabled with `-fcuda-rdc` and my result in performance |
| penalties compared to whole program compilation. Please note that NVIDIA's |
| :program:`nvcc` must be used for linking. |
| |
| Internal API Changes |
| -------------------- |
| |
| These are major API changes that have happened since the 6.0.0 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. |
| |
| - ... |
| |
| AST Matchers |
| ------------ |
| |
| - ... |
| |
| clang-format |
| ------------ |
| |
| - Clang-format will now support detecting and formatting code snippets in raw |
| string literals. This is configured through the `RawStringFormats` style |
| option. |
| |
| - ... |
| |
| libclang |
| -------- |
| |
| ... |
| |
| |
| Static Analyzer |
| --------------- |
| |
| - ... |
| |
| ... |
| |
| 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 <http://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 <http://lists.llvm.org/mailman/listinfo/cfe-dev>`_. |
