llvm dev - Jul 2017 - linker warning while using PluginLoader with PassInfo

Hi,

I tried to write a simple Pass plugin loader to load passes.

Here is the brief steps I did:
1. Declare a command line option like this:
static cl::list<const PassInfo*, bool, PassNameParser>
 PassList(cl::desc(...));

2. include “llvm/Support/PluginLoader.h”

3. Iterate over PassList to get each PassInfo, then invoke getNormalCtor to
construct the pass

Everything goes fine, I can also load plugin normally. However, there are some
warning thrown during link time(of this tool):

ld: warning: direct access in function 'llvm::cl::list<llvm::PassInfo
const*, bool, llvm::PassNameParser>::pri
ntOptionInfo(unsigned long) const' from file
'/usr/local/opt/llvm-clang/current/lib/libLLVMCore.a(LegacyPassMa
nager.cpp.o)' to global weak symbol
'llvm::PassNameParser::ValLessThan(llvm::cl::parser<llvm::PassInfo
const*>
::OptionInfo const*, llvm::cl::parser<llvm::PassInfo const*>::OptionInfo
const*)' from file ‘MY OBJECT FILE' means the weak symbol cannot be
overridden at runtime. This was likely caused by different translation units
being compiled with different visibility settings.

ld: warning: direct access in function
'llvm::PassNameParser::printOptionInfo(llvm::cl::Option const&, unsigned
long) const' from file
'/usr/local/opt/llvm-clang/current/lib/libLLVMCore.a(Pass.cpp.o)' to
global weak symbol
'llvm::PassNameParser::ValLessThan(llvm::cl::parser<llvm::PassInfo
const*>::OptionInfo const*, llvm::cl::parser<llvm::PassInfo
const*>::OptionInfo const*)' from file 'MY OBJECT FILE' means the
weak symbol cannot be overridden at runtime. This was likely caused by different
translation units being compiled with different visibility settings.

ld: warning: direct access in function 'non-virtual thunk to
llvm::PassNameParser::printOptionInfo(llvm::cl::Option const&, unsigned
long) const' from file
'/usr/local/opt/llvm-clang/current/lib/libLLVMCore.a(Pass.cpp.o)' to
global weak symbol
'llvm::PassNameParser::ValLessThan(llvm::cl::parser<llvm::PassInfo
const*>::OptionInfo const*, llvm::cl::parser<llvm::PassInfo
const*>::OptionInfo const*)' from file 'MY OBJECT FILE' means the
weak symbol cannot be overridden at runtime. This was likely caused by different
translation units being compiled with different visibility settings.

I’m not quiet understand what it said. I copy nearly every code related to
plugin loading from the opt tool.
Could somebody answer this?
Thank you

Best Regards,
Bekket McClane