Andrew Morrow: Mainline clang seems to have recently become more strict about the

consistent application of visibility attributes, which causes some new
breakage in libcxxabi:

In file included from src/libcxxabi/src/cxa_default_handlers.cpp:19:
src/libcxxabi/src/private_typeinfo.h:123:23: error: visibility does
not match previous declaration
class __attribute__ ((__visibility__(default))) __class_type_info
                     ^
src/libcxxabi/src/private_typeinfo.h:19:13: note: previous attribute is here
#pragma GCC visibility push(hidden)
           ^
1 error generated.

The forward declaration of __class_type_info is picking up hidden
visibility from the #pragma, which conflicts with the default
visibility applied when the class is later fully declared. I'm
assuming that the full declaration has it right (and that the
diagnostic is correct), so the attached patch applies the default
visibility attribute to the forward declaration.

llvm-svn: 160933