Clang 9.0.0 (In-Progress) Release Notes

Written by the LLVM Team


These are in-progress notes for the upcoming Clang 9 release. Release notes for previous releases can be found on the Download Page.


This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 9.0.0. 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 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 9.0.0?

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

Deprecated Compiler Flags

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

C Language Changes in Clang

C11 Feature Support

C++ Language Changes in Clang

C++1z Feature Support

OpenMP Support in Clang

  • OpenMP 5.0 features
    • Support relational-op != (not-equal) as one of the canonical forms of random access iterator.
    • Added support for mapping of the lambdas in target regions.
    • Added parsing/sema analysis for the requires directive.
    • Support nested declare target directives.
    • Make the this pointer implicitly mapped as map(this[:1]).
    • Added the close map-type-modifier.
  • Various bugfixes and improvements.

New features supported for Cuda devices:

  • Added support for the reductions across the teams.
  • Extended number of constructs that can be executed in SPMD mode.
  • Fixed support for lastprivate/reduction variables in SPMD constructs.
  • New collapse clause scheme to avoid expensive remainder operations.
  • New default schedule for distribute and parallel constructs.
  • Simplified code generation for distribute and parallel in SPMD mode.
  • Flag (-fopenmp_optimistic_collapse) for user to limit collapsed loop counter width when safe to do so.
  • General performance improvement.

Internal API Changes

These are major API changes that have happened since the 8.0.0 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.

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.