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libc++: Perform configuration checks with -nodefaultlibs 

We're compiling libc++ with -nodefaultlibs, so we should also pass this option
during the configuration checks to ensure those checks are consistent with the
actual build.

The primary motivation here is to ease cross-compilation against a non-standard
set of C++ libraries. Previously, the configuration checks would attempt to link
against the standard C++ libraries, which would cause link failures when
cross-compiling, even though the actual library link would go through correctly
(because of the use of -nodefaultlibs and explicitly specifying any needed
libraries). This is more correct even ignoring the motivation, however.

Patch by Shoaib Meenai!

llvm-svn: 279584
This commit is contained in:
Saleem Abdulrasool 2016-08-23 23:01:16 +00:00
parent 84c4cc47f5
commit 12a0b1f4c8
1 changed files with 21 additions and 2 deletions
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23
libcxx/cmake/config-ix.cmake
View File

@ -1,5 +1,26 @@
include(CheckLibraryExists)
include(CheckCXXCompilerFlag)
check_library_exists(c fopen "" LIBCXX_HAS_C_LIB)
check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB)
# libc++ is built with -nodefaultlibs, so we want all our checks to also
# use this option, otherwise we may end up with an inconsistency between
# the flags we think we require during configuration (if the checks are
# performed without -nodefaultlibs) and the flags that are actually
# required during compilation (which has the -nodefaultlibs). libc is
# required for the link to go through.
check_cxx_compiler_flag(-nodefaultlibs LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
list(APPEND CMAKE_REQUIRED_LIBRARIES -nodefaultlibs)
if (LIBCXX_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
if (LIBCXX_HAS_GCC_S_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
endif ()
endif ()
include(CheckLibcxxAtomic)
# Check compiler flags
@ -14,7 +35,5 @@ check_cxx_compiler_flag(/GR- LIBCXX_HAS_NO_GR_FLAG)
# Check libraries
check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB)
check_library_exists(c fopen "" LIBCXX_HAS_C_LIB)
check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB)