What platforms was this tested on? On Aug 22, 2016 9:20 PM, "Shoaib Meenai" <smee...@fb.com> wrote:
> smeenai created this revision. > smeenai added reviewers: beanz, compnerd, EricWF, mclow.lists, rsmith. > smeenai added a subscriber: cfe-commits. > > 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. > > https://reviews.llvm.org/D23791 > > Files: > cmake/config-ix.cmake > > Index: cmake/config-ix.cmake > =================================================================== > --- cmake/config-ix.cmake > +++ 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 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) > > >
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