From ab804284ef5c2e1a1e06cd5e1a9818f0f151078b Mon Sep 17 00:00:00 2001 From: Saleem Abdulrasool Date: Tue, 23 Aug 2016 23:01:16 +0000 Subject: [PATCH] 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! git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@279584 91177308-0d34-0410-b5e6-96231b3b80d8 --- cmake/config-ix.cmake | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake index 3e6c3599d..b4c9ac482 100644 --- a/cmake/config-ix.cmake +++ b/cmake/config-ix.cmake @@ -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)