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| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Mon, 25 May 2020 11:55:54 +0900 |
| parents | 1d019706d866 |
| children | 2e18cbf3894f |
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======================================== Clang 11.0.0 (In-Progress) Release Notes ======================================== .. contents:: :local: :depth: 2 Written by the `LLVM Team <https://llvm.org/>`_ .. warning:: These are in-progress notes for the upcoming Clang 11 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 11.0.0. 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 Git 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 11.0.0? =========================== 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -Wpointer-to-int-cast is a new warning group. This group warns about C-style casts of pointers to a integer type too small to hold all possible values. Non-comprehensive list of changes in this release ------------------------------------------------- - For the ARM target, C-language intrinsics are now provided for the full Arm v8.1-M MVE instruction set. ``<arm_mve.h>`` supports the complete API defined in the Arm C Language Extensions. - For the ARM target, C-language intrinsics ``<arm_cde.h>`` for the CDE instruction set are now provided. - clang adds support for a set of extended integer types (``_ExtInt(N)``) that permit non-power of 2 integers, exposing the LLVM integer types. Since a major motivating use case for these types is to limit 'bit' usage, these types don't automatically promote to 'int' when operations are done between two ``ExtInt(N)`` types, instead math occurs at the size of the largest ``ExtInt(N)`` type. - Users of UBSan, PGO, and coverage on Windows will now need to add clang's library resource directory to their library search path. These features all use runtime libraries, and Clang provides these libraries in its resource directory. For example, if LLVM is installed in ``C:\Program Files\LLVM``, then the profile runtime library will appear at ``C:\Program Files\LLVM\lib\clang\11.0.0\lib\windows\clang_rt.profile-x86_64.lib``. To ensure that the linker can find the appropriate library, users should pass ``/LIBPATH:C:\Program Files\LLVM\lib\clang\11.0.0\lib\windows`` to the linker. If the user links the program with the ``clang`` or ``clang-cl`` drivers, the driver will pass this flag for them. New Compiler Flags ------------------ - -fstack-clash-protection will provide a protection against the stack clash attack for x86 architecture through automatic probing of each page of allocated stack. - -ffp-exception-behavior={ignore,maytrap,strict} allows the user to specify the floating-point exception behavior. The default setting is ``ignore``. - -ffp-model={precise,strict,fast} provides the user an umbrella option to simplify access to the many single purpose floating point options. The default setting is ``precise``. Deprecated Compiler Flags ------------------------- The following options are deprecated and ignored. They will be removed in future versions of Clang. - ... Modified Compiler Flags ----------------------- - -fno-common has been enabled as the default for all targets. Therefore, C code that uses tentative definitions as definitions of a variable in multiple translation units will trigger multiple-definition linker errors. Generally, this occurs when the use of the ``extern`` keyword is neglected in the declaration of a variable in a header file. In some cases, no specific translation unit provides a definition of the variable. The previous behavior can be restored by specifying ``-fcommon``. - -Wasm-ignored-qualifier (ex. `asm const ("")`) has been removed and replaced with an error (this matches a recent change in GCC-9). - -Wasm-file-asm-volatile (ex. `asm volatile ("")` at global scope) has been removed and replaced with an error (this matches GCC's behavior). - Duplicate qualifiers on asm statements (ex. `asm volatile volatile ("")`) no longer produces a warning via -Wduplicate-decl-specifier, but now an error (this matches GCC's behavior). - The deprecated argument ``-f[no-]sanitize-recover`` has changed to mean ``-f[no-]sanitize-recover=all`` instead of ``-f[no-]sanitize-recover=undefined,integer`` and is no longer deprecated. - The argument to ``-f[no-]sanitize-trap=...`` is now optional and defaults to ``all``. - ``-fno-char8_t`` now disables the ``char8_t`` keyword, not just the use of ``char8_t`` as the character type of ``u8`` literals. This restores the Clang 8 behavior that regressed in Clang 9 and 10. - -print-targets has been added to print the registered targets. New Pragmas in Clang -------------------- - ... Attribute Changes in Clang -------------------------- - Attributes can now be specified by clang plugins. See the `Clang Plugins <ClangPlugins.html#defining-attributes>`_ documentation for details. Windows Support --------------- C Language Changes in Clang --------------------------- - The default C language standard used when `-std=` is not specified has been upgraded from gnu11 to gnu17. - Clang now supports the GNU C extension `asm inline`; it won't do anything *yet*, but it will be parsed. - ... C++ Language Changes in Clang ----------------------------- - Clang now implements a restriction on giving non-C-compatible anonymous structs a typedef name for linkage purposes, as described in C++ committee paper `P1766R1 <http://wg21.link/p1766r1>`. This paper was adopted by the C++ committee as a Defect Report resolution, so it is applied retroactively to all C++ standard versions. This affects code such as: .. code-block:: c++ typedef struct { int f() { return 0; } } S; Previous versions of Clang rejected some constructs of this form (specifically, where the linkage of the type happened to be computed before the parser reached the typedef name); those cases are still rejected in Clang 11. In addition, cases that previous versions of Clang did not reject now produce an extension warning. This warning can be disabled with the warning flag ``-Wno-non-c-typedef-for-linkage``. Affected code should be updated to provide a tag name for the anonymous struct: .. code-block:: c++ struct S { int f() { return 0; } }; If the code is shared with a C compilation (for example, if the parts that are not C-compatible are guarded with ``#ifdef __cplusplus``), the typedef declaration should be retained, but a tag name should still be provided: .. code-block:: c++ typedef struct S { int f() { return 0; } } S; C++1z Feature Support ^^^^^^^^^^^^^^^^^^^^^ ... Objective-C Language Changes in Clang ------------------------------------- OpenCL C Language Changes in Clang ---------------------------------- ... ABI Changes in Clang -------------------- OpenMP Support in Clang ----------------------- - ... CUDA Support in Clang --------------------- - ... Internal API Changes -------------------- These are major API changes that have happened since the 10.0.0 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 10.0.0 release of Clang. Users of the build system should adjust accordingly. - clang-tidy and clang-include-fixer are no longer compiled into libclang by default. You can set ``LIBCLANG_INCLUDE_CLANG_TOOLS_EXTRA=ON`` to undo that, but it's expected that that setting will go away eventually. If this is something you need, please reach out to the mailing list to discuss possible ways forward. AST Matchers ------------ - Traversal in AST Matchers was simplified to use the ``TK_IgnoreUnlessSpelledInSource`` mode by default, instead of ``TK_AsIs``. This means that many uses of the ``ignoringImplicit()`` and similar matchers is no longer necessary. Clients of AST Matchers which wish to match on implicit AST nodes can wrap their matcher in ``traverse(TK_AsIs, ...)`` or use ``TraversalKindScope`` if appropriate. The ``clang-query`` tool also uses ``IgnoreUnlessSpelledInSource`` by default. The mode can be changed using ``set traversal AsIs`` in the ``clang-query`` environment. clang-format ------------ - Option ``IndentExternBlock`` has been added to optionally apply indenting inside ``extern "C"`` and ``extern "C++"`` blocks. - ``IndentExternBlock`` option accepts ``AfterExternBlock`` to use the old behavior, as well as Indent and NoIndent options, which map to true and false, respectively. .. code-block:: c++ Indent: NoIndent: #ifdef __cplusplus #ifdef __cplusplus extern "C" { extern "C++" { #endif #endif void f(void); void f(void); #ifdef __cplusplus #ifdef __cplusplus } } #endif #endif - Option ``IndentCaseBlocks`` has been added to support treating the block following a switch case label as a scope block which gets indented itself. It helps avoid having the closing bracket align with the switch statement's closing bracket (when ``IndentCaseLabels`` is ``false``). .. code-block:: c++ switch (fool) { vs. switch (fool) { case 1: case 1: { { bar(); bar(); } break; } default: { break; plop(); default: } { } plop(); } } - Option ``ObjCBreakBeforeNestedBlockParam`` has been added to optionally apply linebreaks for function arguments declarations before nested blocks. - Option ``InsertTrailingCommas`` can be set to ``TCS_Wrapped`` to insert trailing commas in container literals (arrays and objects) that wrap across multiple lines. It is currently only available for JavaScript and disabled by default (``TCS_None``). - Option ``BraceWrapping.BeforeLambdaBody`` has been added to manage lambda line break inside function parameter call in Allman style. .. code-block:: c++ true: connect( []() { foo(); bar(); }); false: connect([]() { foo(); bar(); }); - Option ``AlignConsecutiveBitFields`` has been added to align bit field declarations across multiple adjacent lines .. code-block:: c++ true: bool aaa : 1; bool a : 1; bool bb : 1; false: bool aaa : 1; bool a : 1; bool bb : 1; - Option ``BraceWrapping.BeforeWhile`` has been added to allow wrapping before the ```while`` in a do..while loop. By default the value is (``false``) In previous releases ``IndentBraces`` implied ``BraceWrapping.BeforeWhile``. If using a Custom BraceWrapping style you may need to now set ``BraceWrapping.BeforeWhile`` to (``true``) to be explicit. .. code-block:: c++ true: do { foo(); } while(1); false: do { foo(); } while(1); libclang -------- - ... Static Analyzer --------------- - ... .. _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 ========================== 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 Git 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>`_.