Consistently use code font for command-line flags in the release notes.

Improvements to Clang's diagnostics

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

-  -Wcast-qual was implemented for C++. C-style casts are now properly

-  ``-Wcast-qual`` was implemented for C++. C-style casts are now properly

   diagnosed.

-  -Wunused-lambda-capture warns when a variable explicitly captured

-  ``-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

-  ``-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

-  ``-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

   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

-  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.

New Compiler Flags

------------------

- --autocomplete was implemented to obtain a list of flags and its arguments. This is used for shell autocompletion.

- ``--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

- ``-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.

- ``-fno-slp-vectorize-aggressive`` used to be the default behavior of clang.

New Pragmas in Clang

-----------------------

  vector's elements.

- For compile time constant values, the above rule is weakened to consider the

  value of the scalar constant rather than the constant's type.

- Floating point constants with precise integral representations are not

  implicitly converted to integer values, this is for compatibility with GCC.

  value of the scalar constant rather than the constant's type. However,

  for compatibility with GCC, floating point constants with precise integral

  representations are not implicitly converted to integer values.

Currently the basic integer and floating point types with the following

operators are supported: ``+``, ``/``, ``-``, ``*``, ``%``, ``>``, ``<``,

- 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.

  ``-fsanitize=pointer-overflow``.

  Pointer overflow is an indicator of undefined behavior: when a pointer

  indexing expression wraps around the address space, or produces other

- 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).

  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.