virtual functions not working

supersonic
Nibbie
Posts: 2
Joined: 2010.12
Post: #1
Dec 2, 2010 — 07:33 AM
to simplify, it looks like virtual functions are not working proper, the derived function is not called, but just the base
Code:
-------------------------------------------
class Base {
     virtual void foo();
}

void Base::foo() {
     printf("BASE");
}
-------------------------------------------
class Derived: public Base {
     void foo();
}

void Derived::foo() {
     printf("DERIVED");
}
-------------------------------------------
void test(BASE * basePointer) {
    basePointer->foo();
}
-------------------------------------------
Derived * D = new Derived();
test(D);

outputs BASE Sad
should it output DERIVED??

thank you
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OneSadCookie
Luminary
Posts: 5,131
Joined: 2002.04
Post: #2
Dec 2, 2010 — 11:38 AM
I made your code compilable:

Code:
#include <stdio.h>
//-------------------------------------------
class Base {
public:
virtual void foo();
};

void Base::foo() {
printf("BASE\n");
}
//-------------------------------------------
class Derived: public Base {
public:
void foo();
};

void Derived::foo() {
printf("DERIVED\n");
}
//-------------------------------------------
void test(Base * basePointer) {
basePointer->foo();
}
//-------------------------------------------
int main(){
Derived * D = new Derived();
test(D);
}

And compiled and ran it:
Code:
OneSadMBP13:Desktop keith$ g++ test.cc
OneSadMBP13:Desktop keith$ ./a.out
DERIVED
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compiler
Apprentice
Posts: 8
Joined: 2011.03
Post: #3
Mar 10, 2011 — 06:22 AM
Of course it should print "Derived". D is declared as a Derived *, not a Base * in main(). By the way, you should prefer to include <cstdio> over <stdio.h>. <cstdio> declares everything in <stdio.h> in the std namespace.
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