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libunwind LLVM Unwinder
libunwind is an implementation of the interface defined by the HP libunwind
project. It was contributed by Apple as a way to enable clang++ to port to
platforms that do not have a system unwinder. It is intended to be a small and
fast implementation of the ABI, leaving off some features of HP's libunwind
that never materialized (e.g. remote unwinding).
The unwinder has two levels of API. The high level APIs are the `_Unwind_*`
functions which implement functionality required by `__cxa_*` exception
functions. The low level APIs are the `unw_*` functions which are an interface
defined by the old HP libunwind project.
Getting Started with libunwind
.. toctree::
:maxdepth: 2
Current Status
libunwind is a production-quality unwinder, with platform support for DWARF
unwind info, SjLj, and ARM EHABI.
The low level libunwind API was designed to work either in-process (aka local)
or to operate on another process (aka remote), but only the local path has been
implemented. Remote unwinding remains as future work.
Platform and Compiler Support
libunwind is known to work on the following platforms:
============ ======================== ============ ========================
OS Arch Compilers Unwind Info
============ ======================== ============ ========================
Any i386, x86_64, ARM Clang SjLj
Bare Metal ARM Clang, GCC EHABI
FreeBSD i386, x86_64, ARM64 Clang DWARF CFI
iOS ARM Clang SjLj
Linux ARM Clang, GCC EHABI
Linux i386, x86_64, ARM64 Clang, GCC DWARF CFI
macOS i386, x86_64 Clang, GCC DWARF CFI
NetBSD x86_64 Clang, GCC DWARF CFI
Windows i386, x86_64, ARM, ARM64 Clang DWARF CFI
============ ======================== ============ ========================
The following minimum compiler versions are strongly recommended.
* Clang 3.5 and above
* GCC 4.7 and above.
Anything older *may* work.
Notes and Known Issues
Getting Involved
First please review our `Developer's Policy <>`__
and `Getting started with LLVM <>`__.
**Bug Reports**
If you think you've found a bug in libunwind, please report it using
the `LLVM bug tracker`_. If you're not sure, you
can ask for support on the `Runtimes forum`_ or on IRC.
Please use the tag "libunwind" for new threads.
If you want to contribute a patch to libunwind, the best place for that is
`Phabricator <>`_. Please include [libunwind] in the subject and
add `cfe-commits` as a subscriber. Also make sure you are subscribed to the `cfe-commits mailing list`_.
**Discussion and Questions**
Send discussions and questions to the `Runtimes forum`_. Please add the tag "libunwind" to your post.
Quick Links
* `LLVM Homepage <>`_
* `LLVM Bug Tracker <>`_
* `Clang Discourse Forums <>`_
* `cfe-commits Mailing List <>`_
* `Runtimes Forum <>`_
* `Browse libunwind Sources <>`_