Re: Undefined reference to '...'

[Robert Resendes <resendes@ici.net>]

Are you linking with gcc or g++? Try g++ for the link phase.

Here is the output I get for a simple test program:

------ Begin temp.C --------
#include <iostream.h>

template<class T>
class ancestor {
private:
   T myvar;
public:
   ancestor(T x) { cout << "ancestor()" << endl; myvar = x; }
   ~ancestor() { cout << "~ancestor()" << endl; }
   void dump() { cout << "ancestor.myvar: " << myvar << endl; }
};

int
main( int argc, char* argv ) {
   ancestor<int> something(5);

   something.dump();

   return 0;
}
------ End temp.C --------

> g++     temp.C   -o temp
> temp
ancestor()
ancestor.myvar: 5
~ancestor()

> gcc  temp.C   -o temp
/tmp/cca021531.o: In function `ancestor<int>::~ancestor(void)':
/tmp/cca021531.o(.text+0x6d): undefined reference to `endl(ostream &)'
/tmp/cca021531.o(.text+0x77): undefined reference to `cout'
/tmp/cca021531.o(.text+0x7c): undefined reference to
`ostream::operator<<(char const *)'
/tmp/cca021531.o(.text+0x87): undefined reference to
`ostream::operator<<(ostream &(*)(ostream &))'
/tmp/cca021531.o: In function `ancestor<int>::dump(void)':
/tmp/cca021531.o(.text+0xca): undefined reference to `endl(ostream &)'
/tmp/cca021531.o(.text+0xd7): undefined reference to `cout'
/tmp/cca021531.o(.text+0xdc): undefined reference to
`ostream::operator<<(char const *)'
....



Bob

Orn E. Hansen wrote:

>   I've encountered a condition in GNU C++, where I define the following
> template function...
>
> template<class T>
> class ancestor {
> private:
>  ...
> public:
>  ancestor()
>  ~ancestor()
> };
>
> template<class T>
> ancestor<T>::ancestor()
> {
>  ...
> }
>
> ...
>
> and use it in a main program...
>
> main()
> {
>   ancestor<int> something;
>
>   something...
> }
>
>   The program compiles without errors, but when the linker is to link the
> object files, it is persistent that the reference to 'something' within
> the main program is undefined to 'ancestor<...>'.  Every reference to
> the object 'ancestor<int>' is reported as undefined in the program.
>
>   Does anyone have a clue as to why this occurs, and if there is a cure
> to this?
>
> --
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> debian-user-request@lists.debian.org .
> Trouble?  e-mail to templin@bucknell.edu .



--

-----------------
resendes@ici.net




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