1e03c37b97
This is a second attempt at D101497, which landed as
9a9bc76c0eb72f0f2732c729a460abbd5239c2e3 but had to be reverted in
8cf7ddbdd4e5af966a369e170c73250f2e3920e7.
This issue was that in the case that `COMPILER_RT_INSTALL_PATH` is
empty, expressions like "${COMPILER_RT_INSTALL_PATH}/bin" evaluated to
"/bin" not "bin" as intended and as was originally.
One solution is to make `COMPILER_RT_INSTALL_PATH` always non-empty,
defaulting it to `CMAKE_INSTALL_PREFIX`. D99636 adopted that approach.
But, I think it is more ergonomic to allow those project-specific paths
to be relative the global ones. Also, making install paths absolute by
default inhibits the proper behavior of functions like
`GNUInstallDirs_get_absolute_install_dir` which make relative install
paths absolute in a more complicated way.
Given all this, I will define a function like the one asked for in
https://gitlab.kitware.com/cmake/cmake/-/issues/19568 (and needed for a
similar use-case).
---
Original message:
Instead of using `COMPILER_RT_INSTALL_PATH` through the CMake for
complier-rt, just use it to define variables for the subdirs which
themselves are used.
This preserves compatibility, but later on we might consider getting rid
of `COMPILER_RT_INSTALL_PATH` and just changing the defaults for the
subdir variables directly.
---
There was a seaming bug where the (non-Apple) per-target libdir was
`${target}` not `lib/${target}`. I suspect that has to do with the docs
on `COMPILER_RT_INSTALL_PATH` saying was the library dir when that's no
longer true, so I just went ahead and fixed it, allowing me to define
fewer and more sensible variables.
That last part should be the only behavior changes; everything else
should be a pure refactoring.
---
I added some documentation of these variables too. In particular, I
wanted to highlight the gotcha where `-DSomeCachePath=...` without the
`:PATH` will lead CMake to make the path absolute. See [1] for
discussion of the problem, and [2] for the brief official documentation
they added as a result.
[1]: https://cmake.org/pipermail/cmake/2015-March/060204.html
[2]: https://cmake.org/cmake/help/latest/manual/cmake.1.html#options
In 38b2dec37ee735d5409148e71ecba278caf0f969 the problem was somewhat
misidentified and so `:STRING` was used, but `:PATH` is better as it
sets the correct type from the get-go.
---
D99484 is the main thrust of the `GnuInstallDirs` work. Once this lands,
it should be feasible to follow both of these up with a simple patch for
compiler-rt analogous to the one for libcxx.
Reviewed By: phosek, #libc_abi, #libunwind
Differential Revision: https://reviews.llvm.org/D105765
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.. _BuildingLibunwind:
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==================
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Building libunwind
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==================
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.. contents::
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:local:
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.. _build instructions:
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Getting Started
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===============
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On Mac OS, the easiest way to get this library is to link with -lSystem.
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However if you want to build tip-of-trunk from here (getting the bleeding
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edge), read on.
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The basic steps needed to build libc++ are:
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#. Checkout LLVM, libunwind, and related projects:
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* ``cd where-you-want-llvm-to-live``
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* ``git clone https://github.com/llvm/llvm-project.git``
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#. Configure and build libunwind:
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CMake is the only supported configuration system.
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Clang is the preferred compiler when building and using libunwind.
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* ``cd where you want to build llvm``
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* ``mkdir build``
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* ``cd build``
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* ``cmake -G <generator> -DLLVM_ENABLE_PROJECTS=libunwind [options] <path to llvm sources>``
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For more information about configuring libunwind see :ref:`CMake Options`.
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* ``make unwind`` --- will build libunwind.
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* ``make check-unwind`` --- will run the test suite.
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Shared and static libraries for libunwind should now be present in llvm/build/lib.
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#. **Optional**: Install libunwind
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If your system already provides an unwinder, it is important to be careful
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not to replace it. Remember Use the CMake option ``CMAKE_INSTALL_PREFIX`` to
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select a safe place to install libunwind.
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* ``make install-unwind`` --- Will install the libraries and the headers
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It is sometimes beneficial to build outside of the LLVM tree. An out-of-tree
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build would look like this:
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.. code-block:: bash
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$ cd where-you-want-libunwind-to-live
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$ # Check out llvm, and libunwind
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$ ``svn co https://llvm.org/svn/llvm-project/llvm/trunk llvm``
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$ ``svn co https://llvm.org/svn/llvm-project/libunwind/trunk libunwind``
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$ cd where-you-want-to-build
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$ mkdir build && cd build
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$ export CC=clang CXX=clang++
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$ cmake -DLLVM_PATH=path/to/llvm \
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path/to/libunwind
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$ make
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.. _CMake Options:
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CMake Options
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=============
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Here are some of the CMake variables that are used often, along with a
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brief explanation and LLVM-specific notes. For full documentation, check the
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CMake docs or execute ``cmake --help-variable VARIABLE_NAME``.
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**CMAKE_BUILD_TYPE**:STRING
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Sets the build type for ``make`` based generators. Possible values are
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Release, Debug, RelWithDebInfo and MinSizeRel. On systems like Visual Studio
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the user sets the build type with the IDE settings.
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**CMAKE_INSTALL_PREFIX**:PATH
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Path where LLVM will be installed if "make install" is invoked or the
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"INSTALL" target is built.
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**CMAKE_CXX_COMPILER**:STRING
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The C++ compiler to use when building and testing libunwind.
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.. _libunwind-specific options:
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libunwind specific options
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--------------------------
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.. option:: LIBUNWIND_BUILD_32_BITS:BOOL
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**Default**: Same as LLVM_BUILD_32_BITS
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Toggle whether libunwind should be built with -m32.
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.. option:: LIBUNWIND_ENABLE_ASSERTIONS:BOOL
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**Default**: ``ON``
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Toggle assertions independent of the build mode.
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.. option:: LIBUNWIND_ENABLE_PEDANTIC:BOOL
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**Default**: ``ON``
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Compile with -Wpedantic.
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.. option:: LIBUNWIND_ENABLE_WERROR:BOOL
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**Default**: ``ON``
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Compile with -Werror
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.. option:: LIBUNWIND_ENABLE_SHARED:BOOL
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**Default**: ``ON``
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Build libunwind as a shared library.
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.. option:: LIBUNWIND_ENABLE_STATIC:BOOL
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**Default**: ``ON``
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Build libunwind as a static archive.
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.. option:: LIBUNWIND_ENABLE_CROSS_UNWINDING:BOOL
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**Default**: ``OFF``
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Enable cross-platform unwinding support.
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.. option:: LIBUNWIND_ENABLE_ARM_WMMX:BOOL
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**Default**: ``OFF``
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Enable unwinding support for ARM WMMX registers.
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.. option:: LIBUNWIND_ENABLE_THREADS:BOOL
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**Default**: ``ON``
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Build libunwind with threading support.
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.. option:: LIBUNWIND_TARGET_TRIPLE:STRING
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Target triple for cross compiling
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.. option:: LIBUNWIND_GCC_TOOLCHAIN:PATH
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GCC toolchain for cross compiling
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.. option:: LIBUNWIND_SYSROOT
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Sysroot for cross compiling
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.. option:: LIBUNWIND_INSTALL_LIBRARY_DIR:PATH
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**Default**: ``lib${LIBUNWIND_LIBDIR_SUFFIX}``
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Path where built libunwind libraries should be installed. If a relative path,
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relative to ``CMAKE_INSTALL_PREFIX``.
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