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[libcxx][cmake] Remove libatomic temporarily from CMAKE_REQUIRED_LIBRARIES when configuring

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When libcxx is built in tree for a host which requires libatomic, LLVM's
configuration steps will determine it is required and add it to
CMAKE_REQUIRED_LIBRARIES. When libcxx is later configured, it tests if it
has C++ atomics without libatomic. The test erroneously passes as libatomic
is already part of the set of required libraries.

In turn, a number of the atomic tests will fail as they require libatomic
but the test suite is configured not to use libatomic.

Address this by always dropping libatomic from the set of required libraries
before determining if LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB is true,
then restoring the set of required libraries.

Reviewers: EricWF

Differential Revision: https://reviews.llvm.org/D43509


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@329167 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Simon Dardis
2018-04-04 11:05:03 +00:00
parent cac4ec3986
commit c5121b933d
1 changed files with 7 additions and 0 deletions
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7
cmake/Modules/CheckLibcxxAtomic.cmake
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@@ -31,7 +31,14 @@ int main() {
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_cxx_atomics)
# Perform the check for 64bit atomics without libatomic. It may have been
# added to the required libraries during in the configuration of LLVM, which
# would cause the check for CXX atomics without libatomic to incorrectly pass.
set(OLD_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "atomic")
check_cxx_atomics(LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB)
set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQUIRED_LIBRARIES})
check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
# If not, check if the library exists, and atomics work with it.
if(NOT LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB)