[Bug c++/36022] New: stl templates exported as weak symbols though visibility hidden is used

[Bug c++/36022] New: stl templates exported as weak symbols though visibility hidden is used

[mh+gcc at glandium dot org]

With the following foo.cpp sample:
#include <algorithm>

__attribute__((visibility("default"))) void foo() {
  int array[] = { 23, 5, -10, 0, 0, 321, 1, 2, 99, 30 };
  int elements = sizeof(array) / sizeof(array[0]); 
  std::sort(array, array + elements);
}

Building with the following command line:
g++-4.3 -shared -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -o foo.so
foo.cpp

Leads to internals being exposed, which is unexpected:
objdump -T -C test2.so | grep std
000000000000136d  w   DF .text  000000000000003a  Base        void
std::__unguarded_insertion_sort<int*>(int*, int*)
0000000000001b18  w   DF .text  0000000000000057  Base        void
std::sort<int*>(int*, int*)
000000000000147f  w   DF .text  000000000000000e  Base       
std::__niter_base<int*, false>::__b(int*)
000000000000190b  w   DF .text  0000000000000021  Base        std::__lg(long)
0000000000001324  w   DF .text  0000000000000049  Base        void
std::__unguarded_linear_insert<int*, int>(int*, int)
000000000000141f  w   DF .text  0000000000000060  Base        int*
std::__unguarded_partition<int*, int>(int*, int*, int)
0000000000001674  w   DF .text  0000000000000088  Base        void
std::make_heap<int*>(int*, int*)
0000000000001400  w   DF .text  000000000000001f  Base        void
std::iter_swap<int*, int*>(int*, int*)
00000000000013b5  w   DF .text  000000000000002c  Base        void
std::swap<int>(int&, int&)
00000000000016fc  w   DF .text  0000000000000054  Base        void
std::__pop_heap<int*>(int*, int*, int*)
00000000000019bc  w   DF .text  000000000000004f  Base        int*
std::__copy_move_backward_a2<false, int*, int*>(int*, int*, int*)
0000000000001a4b  w   DF .text  0000000000000079  Base        void
std::__insertion_sort<int*>(int*, int*)
0000000000001a0b  w   DF .text  0000000000000040  Base        int*
std::copy_backward<int*, int*>(int*, int*, int*)
0000000000001750  w   DF .text  000000000000005d  Base        void
std::__heap_select<int*>(int*, int*, int*)
0000000000001284  w   DF .text  00000000000000a0  Base        int const&
std::__median<int>(int const&, int const&, int const&)
00000000000017ad  w   DF .text  000000000000002b  Base        void
std::pop_heap<int*>(int*, int*)
000000000000152e  w   DF .text  0000000000000146  Base        void
std::__adjust_heap<int*, long, int>(int*, long, long, int)
00000000000013a7  w   DF .text  000000000000000e  Base       
std::__miter_base<int*, false>::__b(int*)
000000000000180f  w   DF .text  0000000000000034  Base        void
std::partial_sort<int*>(int*, int*, int*)
00000000000017d8  w   DF .text  0000000000000037  Base        void
std::sort_heap<int*>(int*, int*)
0000000000001991  w   DF .text  000000000000002b  Base        int*
std::__copy_move_backward_a<false, int*, int*>(int*, int*, int*)
0000000000001ac4  w   DF .text  0000000000000054  Base        void
std::__final_insertion_sort<int*>(int*, int*)
0000000000001843  w   DF .text  00000000000000c8  Base        void
std::__introsort_loop<int*, long>(int*, int*, long)
000000000000192c  w   DF .text  0000000000000065  Base        int*
std::__copy_move_backward<false, true,
std::random_access_iterator_tag>::__copy_move_b<int>(int const*, int const*,
int*)
00000000000013e1  w   DF .text  000000000000001f  Base        void
std::__iter_swap<true>::iter_swap<int*, int*>(int*, int*)
000000000000148d  w   DF .text  00000000000000a1  Base        void
std::__push_heap<int*, long, int>(int*, long, long, int)


FYI: g++-4.3 -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure linux gnu
Thread model: posix
gcc version 4.3.1 20080401 (prerelease) (Debian 4.3.0-3) 

(it also happens with g++-4.2 from debian (4.2.3))


-- 
           Summary: stl templates exported as weak symbols though visibility
                    hidden is used
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mh+gcc at glandium dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36022

[Bug libstdc++/36022] stl templates exported as weak symbols though visibility hidden is used

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2008-05-05 05:27 -------
The std:: namespace is supposed to be exposed and is marked as such in the
libstdc++ headers.

So I don't think this is a bug.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |libstdc++


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36022

[Bug libstdc++/36022] stl templates exported as weak symbols though visibility hidden is used

[mh+gcc at glandium dot org]

------- Comment #2 from mh+gcc at glandium dot org  2008-05-11 09:18 -------
Usually, when you're using visibility hidden, that means you want to avoid
exporting a lot of cruft symbols from a shared library... that the std::
namespace is always visibility default is an annoyance. Especially considering
the set of exported symbols change with optimization, since some of these might
end up inlined:

$ g++-4.3 -O3 -shared -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -o
foo.so foo.cpp 
$ objdump -T -C foo.so | grep std
0000000000000780  w   DF .text  00000000000002fe  Base        void
std::__introsort_loop<int*, long>(int*, int*, long)

$ g++-4.3 -O2 -shared -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -o
foo.so foo.cpp 
$ objdump -T -C foo.so | grep std
0000000000000a40  w   DF .text  00000000000000a6  Base        void
std::__insertion_sort<int*>(int*, int*)
00000000000008d0  w   DF .text  0000000000000161  Base        void
std::__introsort_loop<int*, long>(int*, int*, long)
00000000000007e0  w   DF .text  00000000000000eb  Base        void
std::__adjust_heap<int*, long, int>(int*, long, long, int)

$ g++-4.3 -O1 -shared -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -o
foo.so foo.cpp 
$ objdump -T -C foo.so | grep std
0000000000000c65  w   DF .text  0000000000000063  Base        void
std::make_heap<int*>(int*, int*)
0000000000000ee0  w   DF .text  0000000000000051  Base        void
std::__final_insertion_sort<int*>(int*, int*)
0000000000000b52  w   DF .text  0000000000000024  Base        void
std::__unguarded_linear_insert<int*, int>(int*, int)
0000000000000b76  w   DF .text  0000000000000053  Base        void
std::__push_heap<int*, long, int>(int*, long, long, int)
0000000000000b10  w   DF .text  0000000000000042  Base        int*
std::__unguarded_partition<int*, int>(int*, int*, int)
0000000000000d21  w   DF .text  0000000000000053  Base        void
std::sort_heap<int*>(int*, int*)
0000000000000cc8  w   DF .text  0000000000000059  Base        void
std::__heap_select<int*>(int*, int*, int*)
0000000000000e72  w   DF .text  000000000000006a  Base        void
std::__insertion_sort<int*>(int*, int*)
0000000000000d80  w   DF .text  00000000000000f2  Base        void
std::__introsort_loop<int*, long>(int*, int*, long)
0000000000000bc9  w   DF .text  000000000000009c  Base        void
std::__adjust_heap<int*, long, int>(int*, long, long, int)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36022

[Bug libstdc++/36022] stl templates exported as weak symbols though visibility hidden is used

[bkoz at gcc dot gnu dot org]

------- Comment #3 from bkoz at gcc dot gnu dot org  2009-01-30 20:56 -------
Created an attachment (id=17216)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17216&action=view)
remove visibility attribute with -D_GLIBCXX_VISIBILITY=0, run testuite with it
and -fvisibility-hidden


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36022

[Bug libstdc++/36022] stl templates exported as weak symbols though visibility hidden is used

[bkoz at gcc dot gnu dot org]

------- Comment #4 from bkoz at gcc dot gnu dot org  2009-02-04 02:51 -------

This isn't a bug, but rather part of a deliberate linkage strategy. 

For C++, types that are to be used across shared libraries have to be visible.
See:

http://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#Code-Gen-Options

And in particular:

Note that `-fvisibility' does affect C++ vague linkage entities. This means
that, for instance, an exception class that will be thrown between DSOs must be
explicitly marked with default visibility so that the `type_info' nodes will be
unified between the DSOs.

Thus, the rationale for libstdc++ having namespace std have visibility
"default." If you were to hack in support for allowing namespace std to have
hidden visibility, and run the testsuite with -fvisibility=hidden (see attached
patch) you would notice the breakdown in testresults, with mass failures. Thus,
it is provided for information purposes only.

In the libstdc++ source files, anonymous namespaces are used for specific
entities that have both local/hidden linkage. This use of anonymous namespaces
is considered superior to attribute hidden as it uses ISO C++ and is thus more
portable than vendor extensions (pragmas or attributes).

However, in libstdc++ header files, attribute hidden has been difficult to use.
One might think that perhaps all the implementation details could be moved to
say std::__detail, and then marked with attribute hidden. Then, many of these
helper functions would be marked as hidden in your example below.

There are some pitfalls with this approach:

 1) all these implementation base types that are used by default derived
classes  would have to be default
 2) same with implementation details that use static locals
 3) same with virtual functions, etc etc.
 4) thus you end up with a pretty limited set of hidden things

In addition, this may exacerbate the dlopen + RTLD_LOCAL + weak symbol issue
for C++. 


-- 

bkoz at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   GCC host triplet|                            |x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36022

[Bug libstdc++/36022] stl templates exported as weak symbols though visibility hidden is used

[paolo dot carlini at oracle dot com]

------- Comment #5 from paolo dot carlini at oracle dot com  2010-01-09 22:56 -------
I understand this can be closed as invalid, then.


-- 

paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36022