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[Bug c++/21264] New: duplicate symbol warnings for complex template class
- From: "joerg dot richter at pdv-fs dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 28 Apr 2005 12:07:56 -0000
- Subject: [Bug c++/21264] New: duplicate symbol warnings for complex template class
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
/// 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