Some Clang 3.5 release note updates.

**DerivePointerAlignment** (``bool``)

  If ``true``, analyze the formatted file for the most common

  alignment of & and *. ``PointerAlignment`` is then used only as fallback.

  alignment of & and \*. ``PointerAlignment`` is then used only as fallback.

**DisableFormat** (``bool``)

  Disables formatting at all.

these two instantiations, ``twice`` will be optimized (because its definition

was outside the region) and ``thrice`` will not be optimized.

.. _langext-pragma-loop:

Extensions for loop hint optimizations

======================================

- GCC compatibility: Clang displays a warning on unsupported gcc

  optimization flags instead of an error.

- Remarks system: Clang supports `-R` flags for enabling remarks. These are

  diagnostic messages that provide information about the compilation process,

  but don't suggest that a problem has been detected. As such, they cannot

  be upgraded to errors with `-Werror` or `-Rerror`. A `-Reverything` flag

  is provided (paralleling `-Weverything`) to turn on all remarks.

- New remark `-Rpass`: Clang provides information about decisions made by

  optimization passes during compilation. See :ref:`opt_rpass`.

- New warning `-Wabsolute-value`: Clang warns about incorrect or useless usage

  of the absolute functions (`abs`, `fabsf`, etc).

Loop optimization hints can be specified using the new `#pragma clang loop`

directive just prior to the desired loop. The directive allows vectorization,

interleaving, and unrolling to be enabled or disabled. Vector width as well

as interleave and unrolling count can be manually specified.  See language

extensions for details.

as interleave and unrolling count can be manually specified.  See

:ref:`langext-pragma-loop` for details.

Clang now supports the `#pragma unroll` directive to specify loop unrolling

optimization hints.  Placed just prior to the desired loop, `#pragma unroll`

C++ Language Changes in Clang

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

- Reference parameters and return values from functions are more aggressively

  assumed to refer to valid objects when optimizing. Clang will attempt to

  issue a warning by default if it sees null checks being performed on

  references, and `-fsanitize=null` can be used to detect null references

  being formed at runtime.

- ...

C++11 Feature Support

C++17 Feature Support

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

...

Clang has experimental support for some proposed C++1z (tentatively, C++17)

features. This support can be enabled using the `-std=c++1z` flag. The

supported features are:

- `static_assert(expr)` with no message

- `for (identifier : range)` as a synonym for `for (auto &&identifier : range)`

- `template<template<...> typename>` as a synonym for `template<template<...> class>`

Additionally, trigraphs are not recognized by default in this mode.

`-ftrigraphs` can be used if you need to parse legacy code that uses trigraphs.

Note that these features may be changed or removed in future Clang releases

without notice.

Objective-C Language Changes in Clang

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

Clang. If upgrading an external codebase that uses Clang as a library,

this section should help get you past the largest hurdles of upgrading.

...

- Clang uses `std::unique_ptr<T>` in many places where it used to use

  raw `T *` pointers.

libclang

--------

Check for code testing a variable for 0 after using it as a denominator.

This new checker, alpha.core.TestAfterDivZero, catches issues like this:

.. code:: c

.. code-block:: c

  int sum = ...

  int avg = sum / count; // potential division by zero...

The -fno-crash-diagnostics flag can be helpful for speeding the process

of generating a delta reduced test case.

.. _opt_rpass:

Options to Emit Optimization Reports

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