(buildinglibunwind)=

# Building libunwind

:::{contents}
:local: true
:::

(build-instructions)=

## Getting Started

On Mac OS, the easiest way to get this library is to link with -lSystem.
However if you want to build tip-of-trunk from here (getting the bleeding
edge), read on.

The basic steps needed to build libunwind are:

1. Checkout LLVM, libunwind, and related projects:

   - `cd where-you-want-llvm-to-live`
   - `git clone https://github.com/llvm/llvm-project.git`

2. Configure and build libunwind:

   CMake is the only supported configuration system.

   Clang is the preferred compiler when building and using libunwind.

   - `cd where you want to build llvm`
   - `mkdir build`
   - `cd build`
   - `cmake -G <generator> -DLLVM_ENABLE_RUNTIMES=libunwind [options] <llvm-monorepo>/runtimes`

   For more information about configuring libunwind see [CMake Options](#cmake-options).

   - `make unwind` --- will build libunwind.
   - `make check-unwind` --- will run the test suite.

   Shared and static libraries for libunwind should now be present in llvm/build/lib.

3. **Optional**: Install libunwind

   If your system already provides an unwinder, it is important to be careful
   not to replace it. Remember Use the CMake option `CMAKE_INSTALL_PREFIX` to
   select a safe place to install libunwind.

   - `make install-unwind` --- Will install the libraries and the headers

(cmake-options)=

## CMake Options

Here are some of the CMake variables that are used often, along with a
brief explanation and LLVM-specific notes. For full documentation, check the
CMake docs or execute `cmake --help-variable VARIABLE_NAME`.

**CMAKE_BUILD_TYPE**:STRING

: Sets the build type for `make` based generators. Possible values are
  Release, Debug, RelWithDebInfo and MinSizeRel. On systems like Visual Studio
  the user sets the build type with the IDE settings.

**CMAKE_INSTALL_PREFIX**:PATH

: Path where LLVM will be installed if "make install" is invoked or the
  "INSTALL" target is built.

**CMAKE_CXX_COMPILER**:STRING

: The C++ compiler to use when building and testing libunwind.

(libunwind-specific-options)=

### libunwind specific options

:::{option} LIBUNWIND_ENABLE_ASSERTIONS:BOOL

  **Default**: ``ON``

  Toggle assertions independent of the build mode.
:::

:::{option} LIBUNWIND_ENABLE_PEDANTIC:BOOL

  **Default**: ``ON``

  Compile with -Wpedantic.
:::

:::{option} LIBUNWIND_ENABLE_WERROR:BOOL

  **Default**: ``OFF``

  Compile with -Werror
:::

:::{option} LIBUNWIND_ENABLE_SHARED:BOOL

  **Default**: ``ON``

  Build libunwind as a shared library.
:::

:::{option} LIBUNWIND_ENABLE_STATIC:BOOL

  **Default**: ``ON``

  Build libunwind as a static archive.
:::

:::{option} LIBUNWIND_ENABLE_CROSS_UNWINDING:BOOL

  **Default**: ``OFF``

  Enable cross-platform unwinding support.
:::

:::{option} LIBUNWIND_ENABLE_ARM_WMMX:BOOL

  **Default**: ``OFF``

  Enable unwinding support for ARM WMMX registers.
:::

:::{option} LIBUNWIND_ENABLE_THREADS:BOOL

  **Default**: ``ON``

  Build libunwind with threading support.
:::

:::{option} LIBUNWIND_INSTALL_LIBRARY_DIR:PATH

  **Default**: ``lib${LIBUNWIND_LIBDIR_SUFFIX}``

  Path where built libunwind libraries should be installed. If a relative path,
  relative to ``CMAKE_INSTALL_PREFIX``.
:::