[Bug c++/21264] New: duplicate symbol warnings for complex template class

[joerg dot richter at pdv-fs dot de]

/// template.cc /////////////////////////////////////////
struct VirtualBase
{
    virtual ~VirtualBase();
};

struct Foo
{};

struct Bar
{
    virtual ~Bar();
};

template<class OtherBase>
class Test : public VirtualBase, public OtherBase
{
};

void func()
{
  Test<Foo> foo;
  Test<Bar> bar;
}

//////////////////////////////////////////

$ /tools/pkg/gcc/3.4.3/bin/g++ -shared -Wl,-G -o lib343.so template.cc
$ dump -Tv lib343.so | c++filt

IMEX Sclass   Type           IMPid Name
 EXP     DS   Ldef        [noIMid] Test<Bar>::~Test()
 EXP     DS   Ldef        [noIMid] Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] non-virtual thunk to Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] non-virtual thunk to Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] Test<Foo>::~Test()
wEXP     DS SECdef        [noIMid] Test<Foo>::~Test()


$ /tools/pkg/gcc/3.3.3/bin/g++ -shared -Wl,-G -o lib333.so template.cc
$ dump -Tv lib333.so | c++filt

IMEX Sclass   Type           IMPid Name
wEXP     DS SECdef        [noIMid] Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] non-virtual thunk to Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] non-virtual thunk to Test<Bar>::~Test()
wEXP     DS SECdef        [noIMid] Test<Foo>::~Test()
wEXP     DS SECdef        [noIMid] Test<Foo>::~Test()

Note that I edited the dump output to reduce its size.

Here you can see, that the Test<...>::~Test() destructor gets a different IMEX. 
Depending on its template parameter and/or compiler version.

I dont know exactly what the difference between EXP and wEXP is, but I suspect 
that this has something to do with weak symbols. But on the other hand, I 
always read that AIX supports no weak symbols.

Nevertheless, when using the class Test<Bar> in different shared libraries 
which get linked together, you get warnings about duplicate symbols. This 
warnings were not present with GCC 3.3.3.

I am very nervous when seeing duplicate symbols. Especially on AIX. I had great 
times in the past analysing problems with uncaught exceptions that were caused 
by duplicate symbols.

-- 
           Summary: duplicate symbol warnings for complex template class
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: joerg dot richter at pdv-fs dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc-ibm-aix5.2.0.0
  GCC host triplet: powerpc-ibm-aix5.2.0.0
GCC target triplet: powerpc-ibm-aix5.2.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21264