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06-25-2002, 10:46 PM
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#1
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Member
Registered: Sep 2001
Location: Venezuela, Caracas
Distribution: RedHat 9.0
Posts: 196
Rep:
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why compiler gives undefined references on static members???
Heya,
Im getting this weirds undefined references at link-time when compiling a class with static members, any one may know why?
class AMRMesh {
...
static int Dim;
...
static AMRMesh* root;
....
then the errors i get from the member functions that access the static members are from the following kind.:
/tmp/ccqH023E.o(.AMRMesh::gnu.linkonce.t.Neighbour(int, int, AMRMesh *(*)(AMRMesh *, int, int))+0x192): undefined reference to `AMRMesh::RootGrid'
/tmp/ccqH023E.o(.AMRMesh::gnu.linkonce.t.Neighbour(int, int, AMRMesh *(*)(AMRMesh *, int, int))+0x1f3): undefined reference to `AMRMesh:: Dim'
... and lot others which refer to either AMRMesh:: Dim or AMRMesh::RootGrid, which are the only two static members of AMRMesh
Its there some kind of restriction on members functions accessing static members?
why god why?
Last edited by Hano; 06-25-2002 at 10:57 PM.
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06-25-2002, 11:08 PM
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#2
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Senior Member
Registered: Feb 2001
Location: Atlanta, GA
Distribution: Slackware
Posts: 1,821
Rep: 
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What is the version on your compiler and linker?
Code:
g++ --version
ld -version
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06-25-2002, 11:11 PM
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#3
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Member
Registered: Sep 2001
Location: Venezuela, Caracas
Distribution: RedHat 9.0
Posts: 196
Original Poster
Rep:
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g++/gcc 2.96
GNU ld 2.11.90.0.8
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06-25-2002, 11:21 PM
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#4
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Senior Member
Registered: Feb 2001
Location: Atlanta, GA
Distribution: Slackware
Posts: 1,821
Rep: 
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I tried writing a test program with static members and I had no problems linking. Can you post the smallest example possible where you can get the error?
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06-25-2002, 11:28 PM
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#5
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Member
Registered: Sep 2001
Location: Venezuela, Caracas
Distribution: RedHat 9.0
Posts: 196
Original Poster
Rep:
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------------------test.h------------------------------
#include <iostream.h>
class test {
public:
int a;
static int b;
test() {};
~test() {};
void STb() {
cout << b << endl;
};
};
-------------test.cpp
#include "test.h"
int main() {
test* inst;
inst = new (test);
inst->a=3;
inst->b=5;
// test::b=5; neither works
test::STb();
// neither inst->STb() changes nothing
};
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06-26-2002, 12:14 AM
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#6
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Senior Member
Registered: Feb 2001
Location: Atlanta, GA
Distribution: Slackware
Posts: 1,821
Rep: 
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Static variables must be initialized in file scope:
test.cpp
Code:
#include "test.h"
int test::b = 0;
int main()
{
test* inst;
inst = new (test);
inst->a=3;
inst->b=5;
// test::b=5; neither works
test::STb();
// neither inst->STb() changes nothing
};
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06-26-2002, 12:16 AM
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#7
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Senior Member
Registered: Feb 2001
Location: Atlanta, GA
Distribution: Slackware
Posts: 1,821
Rep: 
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I also had to change the member function STb to be static to call it without an object. I'm assuming that was just a typo when creating the example.
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06-26-2002, 12:52 AM
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#8
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Member
Registered: Sep 2001
Location: Venezuela, Caracas
Distribution: RedHat 9.0
Posts: 196
Original Poster
Rep:
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yes, it was a typo because i tried both forms, sorry bout that :^)
... but if a static member has to be intialized outside the class, what happens if i want to make the static variable private? i.e: i want the static variable to be changed/updated/handled/used from the methods implemented by the class, what should i do?
Thx :^)
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06-26-2002, 12:12 PM
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#9
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Senior Member
Registered: Feb 2001
Location: Atlanta, GA
Distribution: Slackware
Posts: 1,821
Rep: 
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Initialize it after the class definition.
test.h
Code:
class test
{
private:
int a;
static int b;
public:
test() {};
~test() {};
void setb( int b1 ) { b = b1; };
void seta( int a1 ) { a = a1; };
static void STb()
{
cout << b << endl;
};
};
int test::b = 0;
test.cpp
Code:
#include "test.h"
int main()
{
test* inst;
inst = new (test);
inst->seta(3);
inst->setb(5);
//test::b=5; error private member
test::STb();
// neither inst->STb() changes nothing
}
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