# Clang 3.1 Release Notes

- Introduction
- What's New in Clang 3.1?
  - Major New Features
  - C Language Changes
  - C++ Language Changes
  - Objective-C Language Changes
  - Internal API Changes
- Known Problems
- Additional Information

Written by the LLVM Team

# These are in-progress notes for the upcoming Clang 3.1 release.
You may prefer the Clang 3.0 Release Notes.

## Introduction

This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 3.1. 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 3.1?

Some of the major new features and improvements to Clang are listed here. Generic improvements to Clang as a whole or two its underlying infrastructure are described first, followed by language-specific sections with improvements to Clang's support for those languages.

### Major New Features

#### Feature 1

...

#### New and better diagnostics

New: `-Wdangling-else`, `-Wstrncat-size`, ...

Improved: `-Wformat`, `-Wempty-body`, ...

### C Language Changes in Clang

#### C11 Feature Support

Clang 3.1 adds support for anonymous structs and anonymous unions, added in the latest ISO C standard. Use `-std=c11` or `-std=gnu11` to enable support for the new language standard. The new C11 features are backwards-compatible and are available as an extension in all language modes.

All warning and language selection flags which previously accepted `c1x` have been updated to accept `c11`. The old `c1x` forms have been removed.

### C++ Language Changes in Clang

#### C++11 Feature Support

Clang 3.1 adds support for more of the language features added in the latest ISO C++ standard, C++ 2011. Use `-std=c++11` or `-std=gnu++11` to enable support for these features. In addition to the features supported by Clang 3.0, the following are now considered to be of production quality:

- Generalized constant expressions
- Lambda expressions
- Generalized initializers
- Unrestricted unions

### Objective-C Language Changes in Clang

Clang 3.1 introduces several new Objective-C language features and improvements.

#### Format string checking for NSString literals

`-Wformat` now checks `@"nsstring literals"`.

### Internal API Changes

These are major API changes that have happened since the 3.0 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.

#### API change 1

...

## 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/doc/`" directory in the Clang tree.

If you have any questions or comments about Clang, please feel free to contact us via the mailing list.