Template/Operator Overload/Linker Error woes

[amhoov]

Hi all,

OS - MacOS X 10.4.9
Compiler - gcc 4.0 (XCode)

I'm *extremely* new to C++ (but have extensive experience with Java),
so please go easy on me.

I'm running into a very odd situation which I believe is related to
template instantiation. I need to include a header file from a library
what includes a template implementation (.cpp) file in which the ==
operator is overloaded. If I include this header file, my application
won't link and gives me the following three errors:

/usr/bin/ld: Undefined symbols:
int operator==<OpenMesh::FaceHandle>(OpenMesh::FaceHandle const&,
OpenMesh::FaceHandle const&)
int operator==<OpenMesh::VertexHandle>(OpenMesh::VertexHandle const&,
OpenMesh::VertexHandle const&)
int operator!=<OpenMesh::HalfedgeHandle>(OpenMesh::HalfedgeHandle
const&, OpenMesh::HalfedgeHandle const&)

The weird part is that the OpenMesh::FaceHandle, VertexHandle, etc.
classes are data structures from a totally separate library. They are
members of the myMesh object (which is also a specialization of a
template) in the main.cpp program.

It seems like for some reason, the linker is looking for an
overloading of the == and != operators that returns int (as defined in
the GA1DArray.h template). The source code for the header which causes
the problem and the main file in which it's included are below. I
apologize for how complicated this code is, but I'm using a couple
different libraries, and it's hard to explain everything briefly.
Lastly, one important bit of information: this code COMPILES AND LINKS
FINE W/ MSVC++ 7.0

Thanks
Aaron
---------

---GAArray.h (Actual included header is ga.h which includes a header
which includes the implementation of a ---template the extends
GAArray, but GAArray has the overload of the operator in question, ==
returning int)

#ifndef _ga_arraytmpl_h_
#define _ga_arraytmpl_h_

template <class T>
class GAArray {
public:
GAArray(unsigned int s) : sz(s), a(sz ? new T[sz] : 0)
{for(unsigned int i=0; i<sz; i++) a = (T)0; }
GAArray(const GAArray<T> & orig){sz=0; a=(T *)0; copy(orig);}
GAArray<T> & operator=(const GAArray<T> & orig){copy(orig); return
*this;}
GAArray<T> & operator=(const T array []) // no err checks!
{for(unsigned int i=0; i<sz; i++) a = *(array+i); return
*this;}
virtual ~GAArray(){delete [] a;}

GAArray<T> * clone(){return new GAArray<T>(*this);}
operator const T * () const {return a;}
operator T * () {return a;}
const T & operator[](unsigned int i) const {return a;}
T & operator[](unsigned int i) {return a;}
void copy(const GAArray<T> & orig){
size(orig.sz);
for(unsigned int i=0; i<sz; i++)
a = orig.a;
}
void copy(const GAArray<T> & orig, unsigned int dest,
unsigned int src, unsigned int length){
for(unsigned int i=0; i<length; i++) a[dest+i] = orig.a[src+i];
}
void move(unsigned int dest, unsigned int src, unsigned int length){
if(src > dest)
for(unsigned int i=0; i<length; i++) a[dest+i] = a[src+i];
else if(src < dest)
for(unsigned int i=length-1; i!=0; i--) a[dest+i] = a[src+i];
}
void swap(unsigned int i, unsigned int j){T tmp=a[j]; a[j]=a;
a=tmp;}
int size() const {return sz;}
int size(unsigned int n){
if(n == sz) return sz;
T * tmp = (n ? new T[n] : 0);
for(int i=((n < sz) ? n-1 : sz-1); i>=0; i--) tmp = a;
delete [] a;
a = tmp;
return sz=n;
}
int equal(const GAArray<T> & b,
unsigned int dest, unsigned int src, unsigned int length) const {
for(unsigned int i=0; i<length; i++)
if(a[dest+i] != b.a[src+i]) return 0;
return 1;
}

protected:
unsigned int sz; // number of elements
T * a; // the contents of the array
};


template <class T> int
operator==(const GAArray<T> & a, const GAArray<T> & b){
if(a.size() != b.size()) return 0;
return a.equal(b,0,0,a.sz);
}
template <class T> int
operator!=(const GAArray<T> & a, const GAArray<T> & b){
if(a.size() != b.size()) return 1;
return a.equal(b,0,0,a.sz) ? 0 : 1;
}

#endif

---------main.cpp------------
#include "MeshObject.h"
#include "ga/ga.h"

Mesh myMesh;


int main(int argc, char **argv)
{
OpenMesh::IO::read_mesh(myMesh, "simple.off");
return 0;
}

 

[Ian Collins]

Hi all,

OS - MacOS X 10.4.9
Compiler - gcc 4.0 (XCode)

I'm *extremely* new to C++ (but have extensive experience with Java),
so please go easy on me.

I'm running into a very odd situation which I believe is related to
template instantiation. I need to include a header file from a library
what includes a template implementation (.cpp) file in which the ==
operator is overloaded. If I include this header file, my application
won't link and gives me the following three errors:

/usr/bin/ld: Undefined symbols:
int operator==<OpenMesh::FaceHandle>(OpenMesh::FaceHandle const&,
OpenMesh::FaceHandle const&)
int operator==<OpenMesh::VertexHandle>(OpenMesh::VertexHandle const&,
OpenMesh::VertexHandle const&)
int operator!=<OpenMesh::HalfedgeHandle>(OpenMesh::HalfedgeHandle
const&, OpenMesh::HalfedgeHandle const&)

Why do these return int rather than bool?

The weird part is that the OpenMesh::FaceHandle, VertexHandle, etc.
classes are data structures from a totally separate library. They are
members of the myMesh object (which is also a specialization of a
template) in the main.cpp program.

Your code doesn't define these operators, are you sure the library does?