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Templated derived classes
- To: gcc at gcc dot gnu dot org
- Subject: Templated derived classes
- From: Matthew Conway <matt_conway at i2 dot com>
- Date: 05 Jul 2000 16:46:16 -0400
Given the following code:
// bug.cpp
//
struct Base
{
virtual ~Base() {};
};
template<class T>
struct Derived : public Base
{
virtual ~Derived() {};
};
int main()
{
Derived<int> tmp;
//Derived tmp;
}
Under AIX with snapshot egcs-20000703, when I try to compile and link
with "g++ -o bug bug.cpp" I get a "Undefined symbol: Derived<int>
virtual table". If I make Derived a non template class, it compiles
and links without a problem. It links fine using gnu ld under x86
linux, its just AIX's ld that I seem to have a problem with. I read
in the faq that templates get instantiated in the file containing the
first non-inline virtual method. I doubt that it applies here as
there is only one file, but tried adding non-inline virtual methods in
Both Base and Derived just to see if it would make a difference, but
it didn't help. Looking at a nm output of bug.o shows that the vtable
of Derived is both defined and undefined...? If anyone has any idea
what the problem is or how I could get this code to link under AIX,
I'd appreciate hearing about it. Thanks,
Matt
Matt
"nm bug.o" after "g++ -c bug.cpp":
._._4Base t 256
._._t7Derived1Zi t 100
.__4Base t 512
.__builtin_delete U -
.__rtti_si U -
.__rtti_user U -
.__t7Derived1Zi t 392
.__tf4Base t 588
.__tft7Derived1Zi t 708
.main T 0
LC..5 d 1196 4
LC..8 d 1204 4
TOC d 1184
_._4Base d 896 12
_._t7Derived1Zi d 884 12
_GLOBAL_.F.main D 1008
__4Base d 968 12
__divss U -
__divus U -
__mulh U -
__mull U -
__quoss U -
__quous U -
__t7Derived1Zi d 908 12
__tf4Base d 980 12
__tft7Derived1Zi d 992 12
__ti4Base B 1208 8
__ti4Base d 1192 4
__tit7Derived1Zi B 1216 12
__tit7Derived1Zi d 1200 4
_aixbug.rw_cpp d 920 48
_aixbug.rw_cpp t 848 21
_vt.4Base d 1184 4
_vt.t7Derived1Zi U -
_vt.t7Derived1Zi d 1188 4
aix-bug.cpp f -
main D 872
main d 872 12