Clang 3.2 Release Notes

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Written by the LLVM Team


This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 3.2. 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 3.2?

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

Clang's diagnostics are constantly being improved to catch more issues, explain them more clearly, and provide more accurate source information about them. The improvements since the 3.1 release include:

Support for tls_model attribute

Clang now supports the tls_model attribute, allowing code that uses thread-local storage to explicitly select which model to use. The available models are "global-dynamic", "local-dynamic", "initial-exec" and "local-exec". See ELF Handling For Thread-Local Storage for more information.

The compiler is free to choose a different model if the specified model is not supported by the target, or if the compiler determines that a more specific model can be used.

Type safety attributes

Clang now supports type safety attributes that allow checking during compile time that 'void *' function arguments and arguments for variadic functions are of a particular type which is determined by some other argument to the same function call.

Usecases include:

See entries for argument_with_type_tag, pointer_with_type_tag and type_tag_for_datatype attributes in Clang language extensions documentation.

Documentation comment support

Clang now supports documentation comments written in a Doxygen-like syntax. Clang parses the comments and can detect syntactic and semantic errors in comments. These warnings are off by default. Pass -Wdocumentation flag to enable warnings about documentation comments.

For example, given:

/// \param [in] Str the string.
/// \returns a modified string.
void do_something(const std::string &str);

clang -Wdocumentation will emit two warnings: warning: '\returns' command used in a comment that is attached to a function returning void [-Wdocumentation]
/// \returns a modified string.
    ~^~~~~~~~~~~~~~~~~~~~~~~~~~ warning: parameter 'Str' not found in the function declaration [-Wdocumentation]
/// \param [in] Str the string.
                ^~~ note: did you mean 'str'?
/// \param [in] Str the string.

libclang includes a new API, clang_FullComment_getAsXML, to convert comments to XML documents. This API can be used to build documentation extraction tools.

New Compiler Flags

C Language Changes in Clang

C11 Feature Support

Clang 3.2 adds support for the C11 _Alignof keyword, pedantic warning through option -Wempty-translation-unit (C11 6.9p1)

C++ Language Changes in Clang

C++11 Feature Support

Clang 3.2 supports most 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 3.1, the following features have been added:

Objective-C Language Changes in Clang

Bug-fixes, no functionality changes.

Python Binding Changes

The following classes and methods have been added:

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.