Re: ld script fails to hide symbols

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Feb 15, 2019 at 1:59 PM Ronghua Zhang <ronghuazhang@gmail.com> wrote:
>
> Thanks. readily -sW gives the same result.
>
> This is the exposed boost symbol
>
> 946: 0000000000000108     8 TLS     LOCAL  DEFAULT   19 _ZN5boost4asio6detail15keyword_tss_ptrINS1_10call_stackINS1_15task_io_serviceENS1_27task_io_service_thread_infoEE7contextEE6value_E

Local symbol isn't exported.

> This is the weak symbol
>
> 116549: 00000000002ab480     9 FUNC    WEAK   DEFAULT   12 _ZNK3api7Service13GetCachedSizeEv

For your case, WEAK == GLOBAL.

H.J.
> On Fri, Feb 15, 2019 at 12:17 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> On Fri, Feb 15, 2019 at 11:33 AM Ronghua Zhang <ronghuazhang@gmail.com> wrote:
>> >
>> > I have a .so library that uses boost and google protobuf. I don't want
>> > symbols from boost and goole protobuf library to be exposed, so I used the
>> > following ldscript:
>> >
>> > {
>> >     global:
>> >         extern "C++" {
>> >             mynamespace::*;
>> >         };
>> >     local: *;
>> > };
>> >
>> > From the output of nm, almost all symbols from boost and google protobuf
>> > disappeared, but a few symbols are left:
>> >
>> > nm -D -C <mylib.so>
>>
>> Don't use nm for these kinds of things.  Please use "readelf -sW" instead.
>>
>> > 0000000000000108 b
>> > boost::asio::detail::keyword_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service,
>> > boost::asio::detail::task_io_service_thread_info>::context>::value_
>> > 0000000000000000 d google::protobuf::internal::ArenaImpl::thread_cache_
>> > 00000000000000d8 b grpc_core::ExecCtx::exec_ctx_
>> >
>> > I also noticed that although most are marked  T as expected, a few
>> > functions in the library as marked weak symbols (W). Why is that?
>> >
>> > 00000000002b5ae0 W mynamespace::ServiceImpl::data_collection() const
>> >
>> > The function is impleme
>>
>>
>>
>> --
>> H.J.



-- 
H.J.