| ======================================== |
| 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. |
| |
| |
| 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). |
| |
| 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. |
| |
| - ... |
| |
| AST Matchers |
| ------------ |
| |
| - ... |
| |
| clang-format |
| ------------ |
| |
| |
| - 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``). |
| |
| - Option ``ObjCBreakBeforeNestedBlockParam`` has been added to optionally apply |
| linebreaks for function arguments declarations before nested blocks. |
| |
| .. code-block:: c++ |
| |
| switch (fool) { vs. switch (fool) { |
| case 1: case 1: { |
| { bar(); |
| bar(); } break; |
| } default: { |
| break; plop(); |
| default: } |
| { } |
| plop(); |
| } |
| } |
| |
| - 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(); |
| }); |
| |
| 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>`_. |