The following simple program doesn't link:
----- Derived.h -----
#ifndef Derived_hh
#define Derived_hh
#include <istream>
#include <ostream>
class D : public std::iostream
{
public:
~D() ;
} ;
#endif
----- Derived.cc -----
#include "Derived.hh"
D::~D()
{
}
----- main.cc -----
#include "Derived.hh"
int
main()
{
D d ;
return 0 ;
}
----- -----
The compiler command was simply "g++ main.cc Derived.cc".
Output was:
----- compiler output -----
/home/kanze/tmp/ccJrgTHi.o(.gnu.linkonce.t._ZN1DC1Ev+0x29): In function
`D::D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.text+0x149): In function `D::~D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.text+0x1fa): In function `D::~D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.text+0x2ac): In function `D::~D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.gnu.linkonce.r._ZTC1D0_Sd+0xc): undefined reference
to `std::basic_iostream<char, std::char_traits<char> >::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.gnu.linkonce.r._ZTC1D0_Sd+0x10): undefined reference
to `std::basic_iostream<char, std::char_traits<char> >::~basic_iostream()'
collect2: ld returned 1 exit status
----- -----
I'm not an expert in your template instantiation strategy, but
when I compile Derived.cc separately, then use nm on the object
file, I find unresolved externals for symbols like std::iostream::~iostream
(which shouldn't exist except as a typedef to a template instantiation,
I think). From what little I understand, I would have expected a
weak definition for the template instantiation (the missing function
in the messages above).
The relevant options I used when building the compiler were:
--enable-threads --enable-__cxa_atexit --disable-nls
(I don't think they have anything to do with the problem, but one
never knows.)
--
James Kanze
--
Summary: Linker errors when deriving from std::iostream
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: critical
Priority: P2
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: james dot kanze at free dot fr
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21056
