Clang 5 documentation

Clang 5.0.0 (In-Progress) Release Notes

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Clang 5.0.0 (In-Progress) Release Notes

Written by the LLVM Team

Warning

These are in-progress notes for the upcoming Clang 5 release. Release notes for previous releases can be found on the Download Page.

Introduction

This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 5.0.0. 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 5.0.0?

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

  • -Wcast-qual was implemented for C++. C-style casts are now properly diagnosed.
  • -Wunused-lambda-capture warns when a variable explicitly captured by a lambda is not used in the body of the lambda.

New Compiler Flags

The option ....

Deprecated Compiler Flags

The following options are deprecated and ignored. They will be removed in future versions of Clang.

  • -fslp-vectorize-aggressive used to enable the BB vectorizing pass. They have been superseeded by the normal SLP vectorizer.
  • -fno-slp-vectorize-aggressive used to be the default behavior of clang.

New Pragmas in Clang

Clang now supports the ...

Attribute Changes in Clang

  • The overloadable attribute now allows at most one function with a given name to lack the overloadable attribute. This unmarked function will not have its name mangled.

Windows Support

Clang’s support for building native Windows programs ...

C Language Changes in Clang

  • ...

...

C11 Feature Support

...

C++ Language Changes in Clang

...

C++1z Feature Support

...

Internal API Changes

These are major API changes that have happened since the 4.0.0 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.

  • ...

clang-format

  • Option BreakBeforeInheritanceComma added to break before : and , in case of multiple inheritance in a class declaration. Enabled by default in the Mozilla coding style.

    true false
    class MyClass
        : public X
        , public Y {
    };
    
    class MyClass : public X, public Y {
    };
    
  • Align block comment decorations.

    Before After
    /* line 1
      * line 2
     */
    
    /* line 1
     * line 2
     */
    
  • The Clang-Format Style Options documentation provides detailed examples for most options.

  • Namespace end comments are now added or updated automatically.

    Before After
    namespace A {
    int i;
    int j;
    }
    
    namespace A {
    int i;
    int j;
    }
    
  • Comment reflow support added. Overly long comment lines will now be reflown with the rest of the paragraph instead of just broken. Option ReflowComments added and enabled by default.

Undefined Behavior Sanitizer (UBSan)

  • The Undefined Behavior Sanitizer has a new check for pointer overflow. This check is on by default. The flag to control this functionality is -fsanitize=pointer-overflow.

    Pointer overflow is an indicator of undefined behavior: when a pointer indexing expression wraps around the address space, or produces other unexpected results, its result may not point to a valid object.

  • UBSan has several new checks which detect violations of nullability annotations. These checks are off by default. The flag to control this group of checks is -fsanitize=nullability. The checks can be individially enabled by -fsanitize=nullability-arg (which checks calls), -fsanitize=nullability-assign (which checks assignments), and -fsanitize=nullability-return (which checks return statements).

  • UBSan can now detect invalid loads from bitfields and from ObjC BOOLs.

  • UBSan can now avoid emitting unnecessary type checks in C++ class methods and in several other cases where the result is known at compile-time. UBSan can also avoid emitting unnecessary overflow checks in arithmetic expressions with promoted integer operands.

New Issues Found

  • ...

Python Binding Changes

The following 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/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.

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