llvm-project/compiler-rt/docs/BuildingCompilerRT.rst

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Prepare Compiler-RT for GnuInstallDirs, matching libcxx, document all 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
2021-04-29 06:36:47 +08:00
.. _BuildingCompilerRT:
===============
Building Compiler-RT
===============
.. contents::
:local:
.. _build instructions:
The instructions on this page are aimed at vendors who ship Compiler-RT as part of an
operating system distribution, a toolchain or similar shipping vehicules. If you
are a user merely trying to use Compiler-RT in your program, you most likely want to
refer to your vendor's documentation, or to the general documentation for using
LLVM, Clang, the various santizers, etc.
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 Compiler-RT.
.. _compiler-rt-specific options:
Compiler-RT specific options
-----------------------
.. option:: COMPILER_RT_INSTALL_PATH:PATH
**Default**: ```` (empty relative path)
Prefix for directories where built Compiler-RT artifacts should be installed.
Can be an absolute path, like the default empty string, in which case it is
relative ``CMAKE_INSTALL_PREFIX``. If setting a relative path, make sure to
include the ``:PATH`` with your ``-D``, i.e. use
``-DCOMPILER_RT_INSTALL_PATH:PATH=...`` not
``-DCOMPILER_RT_INSTALL_PATH=...``, otherwise CMake will convert the
path to an absolute path.
.. option:: COMPILER_RT_INSTALL_LIBRARY_DIR:PATH
**Default**: ``lib``
Path where built Compiler-RT libraries should be installed. If a relative
path, relative to ``COMPILER_RT_INSTALL_PATH``.
.. option:: COMPILER_RT_INSTALL_BINARY_DIR:PATH
**Default**: ``bin``
Path where built Compiler-RT executables should be installed. If a relative
path, relative to ``COMPILER_RT_INSTALL_PATH``.
.. option:: COMPILER_RT_INSTALL_INCLUDE_DIR:PATH
**Default**: ``include``
Path where Compiler-RT headers should be installed. If a relative
path, relative to ``COMPILER_RT_INSTALL_PATH``.
.. option:: COMPILER_RT_INSTALL_DATA_DIR:PATH
**Default**: ``share``
Path where Compiler-RT data should be installed. If a relative
path, relative to ``COMPILER_RT_INSTALL_PATH``.
.. _LLVM-specific variables:
LLVM-specific options
---------------------
.. option:: LLVM_LIBDIR_SUFFIX:STRING
Extra suffix to append to the directory where libraries are to be
installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64``
to install libraries to ``/usr/lib64``.