[PATCH] Always add -lc++abi when using vptr sanitizer on Darwin.

[Nick Kledzik]

Kuba,

I think the logic back when the re-exports were set up was that typeinfo processing was private to libc++abi.dylib.  The public interface was through __dynamic_cast and __cxa_throw.  But now the compiler_rt asan code is walking the raw type_info data structures and expecting to see these types.

 Linking with libc++abi.dylib works for older OS versions.  But, I don’t know what ASan is doing here, or what the long term solution should be. 

-Nick

On Jan 17, 2015, at 9:25 PM, Kuba Brecka <kuba.brecka at gmail.com> wrote:
> I can reproduce on the testcase from https://code.google.com/p/address-sanitizer/issues/detail?id=367:
> 
>  $ ./bin/clang++ a.cpp
>  $ ./bin/clang++ a.cpp -fsanitize=undefined
>  Undefined symbols for architecture x86_64:
>    "typeinfo for __cxxabiv1::__class_type_info", referenced from:
>        __ubsan::checkDynamicType(void*, void*, unsigned long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>        isDerivedFromAtOffset(__cxxabiv1::__class_type_info const*, __cxxabiv1::__class_type_info const*, long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>        findBaseAtOffset(__cxxabiv1::__class_type_info const*, long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>    "typeinfo for __cxxabiv1::__si_class_type_info", referenced from:
>        isDerivedFromAtOffset(__cxxabiv1::__class_type_info const*, __cxxabiv1::__class_type_info const*, long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>        findBaseAtOffset(__cxxabiv1::__class_type_info const*, long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>    "typeinfo for __cxxabiv1::__vmi_class_type_info", referenced from:
>        isDerivedFromAtOffset(__cxxabiv1::__class_type_info const*, __cxxabiv1::__class_type_info const*, long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>        findBaseAtOffset(__cxxabiv1::__class_type_info const*, long) in libclang_rt.ubsan_osx.a(ubsan_type_hash.cc.o)
>  ld: symbol(s) not found for architecture x86_64
>  clang-3.6: error: linker command failed with exit code 1 (use -v to see invocation)
>  $ ./bin/clang++ a.cpp -fsanitize=undefined -lc++abi
>  $
> 
> The mangled names of these are:
> 
>  __ZTIN10__cxxabiv117__class_type_infoE
>  __ZTIN10__cxxabiv120__si_class_type_infoE
>  __ZTIN10__cxxabiv121__vmi_class_type_infoE
> 
> It looks like libc++ is actually re-exporting a lot of symbols from libc++abi, but it doesn't re-export all of them:
> 
>  $ dyldinfo -export /usr/lib/libc++.dylib | grep cxxabiv117__class
>  [re-export] __ZTSN10__cxxabiv117__class_type_infoE (from libc++abi)
>  [re-export] __ZTVN10__cxxabiv117__class_type_infoE (from libc++abi)
>  [re-export] __ZTSN10__cxxabiv117__class_type_infoE (from libc++abi)
>  [re-export] __ZTVN10__cxxabiv117__class_type_infoE (from libc++abi)
>  $ dyldinfo -export /usr/lib/libc++.dylib | grep __ZTIN10__cxxabiv117__class_type_infoE
>  $ 
> 
> So it looks like a libc++ issue (assuming the missing symbols are meant to be re-exported), and they need to be added to libcxx/lib/libc++abi.exp.
> 
> 
> http://reviews.llvm.org/D6960
> 
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