llvm-project/libcxx/cmake
Martin Storsjö 529a79302b Reapply #2 of [runtimes] Fix building initial libunwind+libcxxabi+libcxx with compiler implied -lunwind
This does mostly the same as D112126, but for the runtimes cmake files.
Most of that is straightforward, but the interdependency between
libcxx and libunwind is tricky:

Libunwind is built at the same time as libcxx, but libunwind is not
installed yet. LIBCXXABI_USE_LLVM_UNWINDER makes libcxx link directly
against the just-built libunwind, but the compiler implicit -lunwind
isn't found. This patch avoids that by adding --unwindlib=none if
supported, if we are going to link explicitly against a newly built
unwinder anyway.

Since the previous attempt, this no longer uses
llvm_enable_language_nolink (and thus doesn't set
CMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY during the compiler
sanity checks). Setting CMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY
during compiler sanity checks makes cmake not learn about some
aspects of the compiler, which can make further find_library or
find_package fail. This caused OpenMP to not detect libelf and libffi,
disabling some OpenMP target plugins.

Instead, require the caller to set CMAKE_{C,CXX}_COMPILER_WORKS=YES
when building in a configuration with an incomplete toolchain.

Differential Revision: https://reviews.llvm.org/D113253
2021-12-09 21:38:14 +02:00
..
Modules [CMake] Cache the compiler-rt library search results 2021-10-27 17:53:03 -07:00
caches [runtimes] Remove support for GCC-style 32 bit multilib builds 2021-12-01 12:57:01 -05:00
config-ix.cmake Reapply #2 of [runtimes] Fix building initial libunwind+libcxxabi+libcxx with compiler implied -lunwind 2021-12-09 21:38:14 +02:00