| ======================= |
| Clang 3.4 Release Notes |
| ======================= |
| |
| .. contents:: |
| :local: |
| :depth: 2 |
| |
| Introduction |
| ============ |
| |
| This document contains the release notes for the Clang C/C++/Objective-C |
| frontend, part of the LLVM Compiler Infrastructure, release 3.4. 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 <http://llvm.org/docs/ReleaseNotes.html>`_. All LLVM |
| releases may be downloaded from the `LLVM releases web |
| site <http://llvm.org/releases/>`_. |
| |
| For more information about Clang or LLVM, including information about the |
| latest release, please check out the main `Clang Web Site |
| <http://clang.llvm.org>`_ or the `LLVM Web Site <http://llvm.org>`_. |
| |
| 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 <http://llvm.org/releases/>`_. |
| |
| What's New in Clang 3.4.1? |
| ========================== |
| |
| * Various bug fixes for AArch64, ARM, and PowerPC targets |
| |
| * C++11 fixes |
| |
| What's New in Clang 3.4? |
| ======================== |
| |
| 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. |
| |
| Last release which will build as C++98 |
| -------------------------------------- |
| |
| This is expected to be the last release of Clang which compiles using a C++98 |
| toolchain. We expect to start using some C++11 features in Clang starting after |
| this release. That said, we are committed to supporting a reasonable set of |
| modern C++ toolchains as the host compiler on all of the platforms. This will |
| at least include Visual Studio 2012 on Windows, and Clang 3.1 or GCC 4.7.x on |
| Mac and Linux. The final set of compilers (and the C++11 features they support) |
| is not set in stone, but we wanted users of Clang to have a heads up that the |
| next release will involve a substantial change in the host toolchain |
| requirements. |
| |
| Note that this change is part of a change for the entire LLVM project, not just |
| Clang. |
| |
| 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 3.3 release include: |
| |
| - -Wheader-guard warns on mismatches between the #ifndef and #define lines |
| in a header guard. |
| |
| .. code-block:: c |
| |
| #ifndef multiple |
| #define multi |
| #endif |
| |
| returns |
| `warning: 'multiple' is used as a header guard here, followed by #define of a different macro [-Wheader-guard]` |
| |
| - -Wlogical-not-parentheses warns when a logical not ('!') only applies to the |
| left-hand side of a comparison. This warning is part of -Wparentheses. |
| |
| .. code-block:: c++ |
| |
| int i1 = 0, i2 = 1; |
| bool ret; |
| ret = !i1 == i2; |
| |
| returns |
| `warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]` |
| |
| |
| - Boolean increment, a deprecated feature, has own warning flag |
| -Wdeprecated-increment-bool, and is still part of -Wdeprecated. |
| - Clang errors on builtin enum increments and decrements in C++. |
| |
| .. code-block:: c++ |
| |
| enum A { A1, A2 }; |
| void test() { |
| A a; |
| a++; |
| } |
| |
| returns |
| `error: cannot increment expression of enum type 'A'` |
| |
| |
| - -Wloop-analysis now warns on for-loops which have the same increment or |
| decrement in the loop header as the last statement in the loop. |
| |
| .. code-block:: c |
| |
| void foo(char *a, char *b, unsigned c) { |
| for (unsigned i = 0; i < c; ++i) { |
| a[i] = b[i]; |
| ++i; |
| } |
| } |
| |
| returns |
| `warning: variable 'i' is incremented both in the loop header and in the loop body [-Wloop-analysis]` |
| |
| - -Wuninitialized now performs checking across field initializers to detect |
| when one field in used uninitialized in another field initialization. |
| |
| .. code-block:: c++ |
| |
| class A { |
| int x; |
| int y; |
| A() : x(y) {} |
| }; |
| |
| returns |
| `warning: field 'y' is uninitialized when used here [-Wuninitialized]` |
| |
| - Clang can detect initializer list use inside a macro and suggest parentheses |
| if possible to fix. |
| - Many improvements to Clang's typo correction facilities, such as: |
| |
| + Adding global namespace qualifiers so that corrections can refer to shadowed |
| or otherwise ambiguous or unreachable namespaces. |
| + Including accessible class members in the set of typo correction candidates, |
| so that corrections requiring a class name in the name specifier are now |
| possible. |
| + Allowing typo corrections that involve removing a name specifier. |
| + In some situations, correcting function names when a function was given the |
| wrong number of arguments, including situations where the original function |
| name was correct but was shadowed by a lexically closer function with the |
| same name yet took a different number of arguments. |
| + Offering typo suggestions for 'using' declarations. |
| + Providing better diagnostics and fixit suggestions in more situations when |
| a '->' was used instead of '.' or vice versa. |
| + Providing more relevant suggestions for typos followed by '.' or '='. |
| + Various performance improvements when searching for typo correction |
| candidates. |
| |
| - `LeakSanitizer <LeakSanitizer.html>`_ is an experimental memory leak detector |
| which can be combined with AddressSanitizer. |
| |
| New Compiler Flags |
| ------------------ |
| |
| - Clang no longer special cases -O4 to enable lto. Explicitly pass -flto to |
| enable it. |
| - Clang no longer fails on >= -O5. These flags are mapped to -O3 instead. |
| - Command line "clang -O3 -flto a.c -c" and "clang -emit-llvm a.c -c" |
| are no longer equivalent. |
| - Clang now errors on unknown -m flags (``-munknown-to-clang``), |
| unknown -f flags (``-funknown-to-clang``) and unknown |
| options (``-what-is-this``). |
| |
| C Language Changes in Clang |
| --------------------------- |
| |
| - Added new checked arithmetic builtins for security critical applications. |
| |
| C++ Language Changes in Clang |
| ----------------------------- |
| |
| - Fixed an ABI regression, introduced in Clang 3.2, which affected |
| member offsets for classes inheriting from certain classes with tail padding. |
| See `PR16537 <http://llvm.org/PR16537>`_. |
| |
| - Clang 3.4 supports the 2013-08-28 draft of the ISO WG21 SG10 feature test |
| macro recommendations. These aim to provide a portable method to determine |
| whether a compiler supports a language feature, much like Clang's |
| |has_feature macro|_. |
| |
| .. |has_feature macro| replace:: ``__has_feature`` macro |
| .. _has_feature macro: LanguageExtensions.html#has-feature-and-has-extension |
| |
| C++1y Feature Support |
| ^^^^^^^^^^^^^^^^^^^^^ |
| |
| Clang 3.4 supports all the features in the current working draft of the |
| upcoming C++ standard, provisionally named C++1y. Support for the following |
| major new features has been added since Clang 3.3: |
| |
| - Generic lambdas and initialized lambda captures. |
| - Deduced function return types (``auto f() { return 0; }``). |
| - Generalized ``constexpr`` support (variable mutation and loops). |
| - Variable templates and static data member templates. |
| - Use of ``'`` as a digit separator in numeric literals. |
| - Support for sized ``::operator delete`` functions. |
| |
| In addition, ``[[deprecated]]`` is now accepted as a synonym for Clang's |
| existing ``deprecated`` attribute. |
| |
| Use ``-std=c++1y`` to enable C++1y mode. |
| |
| OpenCL C Language Changes in Clang |
| ---------------------------------- |
| |
| - OpenCL C "long" now always has a size of 64 bit, and all OpenCL C |
| types are aligned as specified in the OpenCL C standard. Also, |
| "char" is now always signed. |
| |
| Internal API Changes |
| -------------------- |
| |
| These are major API changes that have happened since the 3.3 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. |
| |
| Wide Character Types |
| ^^^^^^^^^^^^^^^^^^^^ |
| |
| The ASTContext class now keeps track of two different types for wide character |
| types: WCharTy and WideCharTy. WCharTy represents the built-in wchar_t type |
| available in C++. WideCharTy is the type used for wide character literals; in |
| C++ it is the same as WCharTy, but in C99, where wchar_t is a typedef, it is an |
| integer type. |
| |
| Static Analyzer |
| --------------- |
| |
| The static analyzer has been greatly improved. This impacts the overall analyzer quality and reduces a number of false positives. |
| In particular, this release provides enhanced C++ support, reasoning about initializer lists, zeroing constructors, noreturn destructors and modeling of destructor calls on calls to delete. |
| |
| Clang Format |
| ------------ |
| |
| Clang now includes a new tool ``clang-format`` which can be used to |
| automatically format C, C++ and Objective-C source code. ``clang-format`` |
| automatically chooses linebreaks and indentation and can be easily integrated |
| into editors, IDEs and version control systems. It supports several pre-defined |
| styles as well as precise style control using a multitude of formatting |
| options. ``clang-format`` itself is just a thin wrapper around a library which |
| can also be used directly from code refactoring and code translation tools. |
| More information can be found on `Clang Format's |
| site <http://clang.llvm.org/docs/ClangFormat.html>`_. |
| |
| Windows Support |
| --------------- |
| |
| - `clang-cl <UsersManual.html#clang-cl>`_ provides a new driver mode that is |
| designed for compatibility with Visual Studio's compiler, cl.exe. This driver |
| mode makes Clang accept the same kind of command-line options as cl.exe. The |
| installer will attempt to expose clang-cl in any Visual Studio installations |
| on the system as a Platform Toolset, e.g. "LLVM-vs2012". clang-cl targets the |
| Microsoft ABI by default. Please note that this driver mode and compatibility |
| with the MS ABI is highly experimental. |
| |
| 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 <http://clang.llvm.org/>`_. The web page contains versions of the |
| API documentation which are up-to-date with the Subversion revision of |
| the source code. You can access versions of these documents specific to |
| this release by going into the "``clang/docs/``" directory in the Clang |
| tree. |
| |
| If you have any questions or comments about Clang, please feel free to |
| contact us via the `mailing |
| list <http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev>`_. |