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[libcxxabi] Prevent cmake from removing our explicit system C++ include paths 

We build with `-nostdinc++` and add our own header path via
`LIBCXXABI_LIBCXX_INCLUDES`.  However cmake tried to be clever and if
`LIBCXXABI_LIBCXX_INCLUDES` happens to match the compilers system path
it will remove the `-I` flag meaning we can't access any C++ headers.

Ideally cmake would be able see that we are using `-nostdinc++` and
disable this behaviour.

Differential Revision: https://reviews.llvm.org/D69973
This commit is contained in:
Sam Clegg 2019-11-07 14:51:25 -08:00
parent ef150e2ea5
commit 4230fa9390
1 changed files with 7 additions and 0 deletions
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7
libcxxabi/CMakeLists.txt
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@ -270,6 +270,13 @@ include(config-ix)
if (LIBCXXABI_HAS_NOSTDINCXX_FLAG)
list(APPEND LIBCXXABI_COMPILE_FLAGS -nostdinc++)
# cmake 3.14 and above remove system include paths that are explicitly
# passed on the command line. We build with -nostdinc++ and explicitly add
# just the libcxx system include paths with -I on the command line.
# Setting CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES effectively prevents cmake
# from removing these.
# See: https://gitlab.kitware.com/cmake/cmake/issues/19227
set(CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES "")
# Remove -stdlib flags to prevent them from causing an unused flag warning.
string(REPLACE "-stdlib=libc++" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
string(REPLACE "-stdlib=libstdc++" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")