Clang 3.2 Release Notes
These are in-progress notes for the upcoming Clang 3.2
release.
You may prefer the
Clang 3.1
Release Notes.
Introduction
This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 3.2. 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:
- -Wuninitialized has been taught to recognise uninitialized uses
which always occur when an explicitly-written non-constant condition is either
true or false. For example:
int f(bool b) { int n; if (b) n = 1; return n; } sometimes-uninit.cpp:3:7: warning: variable 'n' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized] if (b) ^ sometimes-uninit.cpp:5:10: note: uninitialized use occurs here return n; ^ sometimes-uninit.cpp:3:3: note: remove the 'if' if its condition is always true if (b) ^~~~~~ sometimes-uninit.cpp:2:8: note: initialize the variable 'n' to silence this warning int n; ^ = 0
This functionality can be enabled or disabled separately from -Wuninitialized with the -Wsometimes-uninitialized warning flag.
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.
New Compiler Flags
- -gline-tables-only controls the size of debug information. This flag tells Clang to emit debug info which is just enough to obtain stack traces with function names, file names and line numbers (by such tools as gdb or addr2line). Debug info for variables or function parameters is not produced, which reduces the size of the resulting binary.
C Language Changes in Clang
C11 Feature Support
...
C++ Language Changes in Clang
C++11 Feature Support
...
Objective-C Language Changes in Clang
...
Internal API Changes
These are major API changes that have happened since the 3.1 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
...
Python Binding Changes
The following methods have been added:- ...
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.