======================================= Clang 5.0.0 (In-Progress) Release Notes ======================================= .. contents:: :local: :depth: 2 Written by the `LLVM Team `_ .. warning:: These are in-progress notes for the upcoming Clang 5 release. Release notes for previous releases can be found on `the Download Page `_. Introduction ============ This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 5.0.0. 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 `_. All LLVM releases may be downloaded from the `LLVM releases web site `_. For more information about Clang or LLVM, including information about the latest release, please check out the main please see the `Clang Web Site `_ or the `LLVM Web Site `_. 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 `_. What's New in Clang 5.0.0? ========================== 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -Wcast-qual was implemented for C++. C-style casts are now properly diagnosed. - -Wunused-lambda-capture warns when a variable explicitly captured by a lambda is not used in the body of the lambda. - -Wstrict-prototypes is a new warning that warns about non-prototype function and block declarations and types in C and Objective-C. - -Wunguarded-availability is a new warning that warns about uses of new APIs that were introduced in a system whose version is newer than the deployment target version. A new Objective-C expression ``@available`` has been introduced to perform system version checking at runtime. This warning is off by default to prevent unexpected warnings in existing projects. However, its less strict sibling -Wunguarded-availability-new is on by default. It warns about unguarded uses of APIs only when they were introduced in or after macOS 10.13, iOS 11, tvOS 11 or watchOS 4. - The -Wdocumentation warning now allows the use of ``\param`` and ``\returns`` documentation directives in the documentation comments for declarations with a function or a block pointer type. - The compiler no longer warns about unreachable ``__builtin_unreachable`` statements. New Compiler Flags ------------------ - --autocomplete was implemented to obtain a list of flags and its arguments. This is used for shell autocompletion. Deprecated Compiler Flags ------------------------- The following options are deprecated and ignored. They will be removed in future versions of Clang. - -fslp-vectorize-aggressive used to enable the BB vectorizing pass. They have been superseeded by the normal SLP vectorizer. - -fno-slp-vectorize-aggressive used to be the default behavior of clang. New Pragmas in Clang ----------------------- Clang now supports the ... Attribute Changes in Clang -------------------------- - The ``overloadable`` attribute now allows at most one function with a given name to lack the ``overloadable`` attribute. This unmarked function will not have its name mangled. - The ```ms_abi`` attribute and the ``__builtin_ms_va_list`` types and builtins are now supported on AArch64. 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 ---------------------------------- ... Internal API Changes -------------------- These are major API changes that have happened since the 4.0.0 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 ------------ * Option **BreakBeforeInheritanceComma** added to break before ``:`` and ``,`` in case of multiple inheritance in a class declaration. Enabled by default in the Mozilla coding style. +---------------------+----------------------------------------+ | true | false | +=====================+========================================+ | .. code-block:: c++ | .. code-block:: c++ | | | | | class MyClass | class MyClass : public X, public Y { | | : public X | }; | | , public Y { | | | }; | | +---------------------+----------------------------------------+ * Align block comment decorations. +----------------------+---------------------+ | Before | After | +======================+=====================+ | .. code-block:: c++ | .. code-block:: c++ | | | | | /* line 1 | /* line 1 | | * line 2 | * line 2 | | */ | */ | +----------------------+---------------------+ * The :doc:`ClangFormatStyleOptions` documentation provides detailed examples for most options. * Namespace end comments are now added or updated automatically. +---------------------+---------------------+ | Before | After | +=====================+=====================+ | .. code-block:: c++ | .. code-block:: c++ | | | | | namespace A { | namespace A { | | int i; | int i; | | int j; | int j; | | } | } | +---------------------+---------------------+ * Comment reflow support added. Overly long comment lines will now be reflown with the rest of the paragraph instead of just broken. Option **ReflowComments** added and enabled by default. libclang -------- ... Static Analyzer --------------- - The static analyzer now supports using the `z3 theorem prover `_ from Microsoft Research as an external constraint solver. This allows reasoning over more complex queries, but performance is ~15x slower than the default range-based constraint solver. To enable the z3 solver backend, clang must be built with the ``CLANG_ANALYZER_BUILD_Z3=ON`` option, and the ``-Xanalyzer -analyzer-constraints=z3`` arguments passed at runtime. Undefined Behavior Sanitizer (UBSan) ------------------------------------ - The Undefined Behavior Sanitizer has a new check for pointer overflow. This check is on by default. The flag to control this functionality is -fsanitize=pointer-overflow. Pointer overflow is an indicator of undefined behavior: when a pointer indexing expression wraps around the address space, or produces other unexpected results, its result may not point to a valid object. - UBSan has several new checks which detect violations of nullability annotations. These checks are off by default. The flag to control this group of checks is -fsanitize=nullability. The checks can be individially enabled by -fsanitize=nullability-arg (which checks calls), -fsanitize=nullability-assign (which checks assignments), and -fsanitize=nullability-return (which checks return statements). - UBSan can now detect invalid loads from bitfields and from ObjC BOOLs. - UBSan can now avoid emitting unnecessary type checks in C++ class methods and in several other cases where the result is known at compile-time. UBSan can also avoid emitting unnecessary overflow checks in arithmetic expressions with promoted integer operands. Core Analysis Improvements ========================== - ... New Issues Found ================ - ... Python Binding Changes ---------------------- Python bindings now support both Python 2 and Python 3. The following methods have been added: - ``is_scoped_enum`` has been added to ``Cursor``. - ``exception_specification_kind`` has been added to ``Cursor``. - ``get_address_space`` has been added to ``Type``. - ``get_typedef_name`` has been added to ``Type``. - ``get_exception_specification_kind`` has been added to ``Type``. - ... Significant Known Problems ========================== Additional Information ====================== A wide variety of additional information is available on the `Clang web page `_. 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 `_.