This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 9 years ago.
Error 1 error LNK2019: unresolved external symbol "bool __cdecl
prefix(unsigned int,unsigned int)" (?prefix##YA_NII#Z) referenced in
function _main c:\Users\Work\documents\visual studio
2012\Projects\Book\Project5\Project5\Source.obj Project5
Error 2 error LNK1120: 1 unresolved
externals c:\users\work\documents\visual studio
2012\Projects\Book\Project5\Debug\Project5.exe 1 1 Project5
I just..I dont even know what I have to ask you guys. How do I fix this?
This is the code:
#include <iostream>
#include <string>
#include <vector>
#include <math.h>
using namespace std;
void citire(vector<unsigned int> myVector,int &nrElem);
bool prefix(unsigned int nr1,unsigned int nr2);
int main(){
int nrElem={0};
vector<unsigned int> myVector;
//citire(myVector,nrElem);
cout << prefix(123,1234);
system("pause");
return 0;
}
void citire(vector<unsigned int> myVector,int &nrElem){
cout << "NumarElemente=" ;
cin >> nrElem ;
for(int i=0;i<nrElem;i++){
unsigned int nrCitit;
cout << "Elem #" << i+1 <<"=";
cin >> nrCitit;
myVector.push_back(nrCitit);
};
for(int i=0;i<nrElem;i++){
cout << myVector.at(i);
};
}
bool prefix(unsigned int &nr1,unsigned int &nr2){
unsigned int nr1copy=nr1;
unsigned int nr2copy=nr2;
int digitsNr1 = 0; while (nr1copy != 0) { nr1copy /= 10; digitsNr1++; }
int digitsNr2 = 0; while (nr2copy != 0) { nr2copy /= 10; digitsNr1++; }
if ( nr2/_Pow_int(10,digitsNr2-digitsNr1)==nr1) {return true;}
else return false;
}
bool prefix(unsigned int nr1,unsigned int nr2);
is not same as
bool prefix(unsigned int& nr1,unsigned int &nr2);
In forward forward declaration, you are taking the parameters by value but in the definition it is by reference. Keep the argument types same in the declaration and the definition.
unresolved external symbol "bool __cdecl prefix(unsigned int,unsigned int)"
Usually when you see these kind of linker errors, the first thing you need to check is if the function's declaration and definition signatures match or not. In this case, it is clearly not.
Declaration:
bool prefix(unsigned int nr1,unsigned int nr2);
definition:
bool prefix(unsigned int &nr1,unsigned int &nr2){ ... }
See the difference? Both should be the same. Looking at your code, it looks like you should keep the version in the declaration.
You have a prototype for the prefix() function:
bool prefix(unsigned int nr1,unsigned int nr2);
which has a signature that differs from the implementation given below:
bool prefix(unsigned int &nr1,unsigned int &nr2) {
^^^ ^^^
....
}
Note that in the prototype, the nr1 and nr2 parameters are passed by value; instead, in the implementation signature, they are passed by reference (note the &).
Both prototype and implementation signatures should match. Fix the wrong one.
(Note: since you can't pass literals like the 123 in main() as non-const reference, I think the wrong one is the implementation signature, i.e. drop the & in the implementation signature).
Related
This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 3 years ago.
I am using static variable. After referring to Unresolved external symbol on static class members, I modified the program with Abc::ct
#include <iostream>
class Abc
{
private:
static unsigned int ct;
public:
void f1()
{
for (int i = 0; i < 5; ++i)
f2();
}
void f2() {
Abc::ct = 0;
if (Abc::ct == 0)
std::cout << "Zero iteration\n";
std::cout << Abc::ct << "\t";
++Abc::ct;
}
};
int main()
{
Abc obj;
obj.f1();
}
but getting error as error LNK2001: unresolved external symbol "private: static unsigned int Abc::ct" in MSVC or undefined reference to Abc::ct in g++. How can I define static variable in class Abc?
You declared your static variable, but you did not define and initialize it. Above main(), but outside of your class, add the following line:
unsigned int Abc::ct = 0;
or, if you are using C++17, you can change your:
static unsigned int ct;
to:
static inline unsigned int ct = 0;
You have to define it:
unsigned int Abc::ct = 0;
Demo
This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 3 years ago.
This problem has been solved before, but I've been looking all over, and none of those explains how to fix this, the situation i'm in. Most of them is about external libraries.
I'm trying to test my code. I've made a test class and that class is trying to access another class by including that class's header file. But when I'm trying to call its function it just gives me an unresolved external symbol error.
This is my current attempt. Here I'm trying to access the other classes's header file to call it's functions.
CardTest.cpp
#include <iostream>
#include "../Header Files/Hand.h"
#include "../Header Files/HandValueCalculator.h"
using namespace std;
HandValueCalculator handValueCalculator;
Hand hand;
void Test() {
bool value = handValueCalculator.DoesHandHaveAce(&hand.cards);
cout << value << endl;
}
HandValueCalculator.h
#ifndef HANDVALUECALCULATOR_H_INCLUDED
#define HANDVALUECALCULATOR_H_INCLUDED
#include <vector>
#include "../Header Files/Card.h"
class HandValueCalculator {
public:
HandValueCalculator();
bool DoesHandHaveAce(std::vector<Card>* cards);
int GetValueWithoutAce(std::vector<Card>* cards);
int GetValueWithAce(std::vector<Card>* cards);
};
#endif // HANDVALUECALCULATOR_H_INCLUDED
HandValueCalculator.cpp
#include "../Header Files/HandValueCalculator.h"
HandValueCalculator::HandValueCalculator() {
}
bool HandValueCalculator::DoesHandHaveAce(std::vector<Card>* cards) {
int i;
for (i = 0; i < cards.size(); i++) {
if (cards.at(i).GetValue() == 11) {
return true;
}
}
return false;
}
int HandValueCalculator::GetValueWithoutAce(std::vector<Card>* cards) {
for (i = 0; i < cards.size(); i++) {
int cardValue = cards.at(i).GetValue()
totalValue = totalValue + cardValue;
}
return 0;
}
int HandValueCalculator::GetValueWithAce(std::vector<Card>* cards) {
return 0;
}
This is the error I'm getting, and I don't think the compiler recognizes that the functions have a body, and because it can't find a body for the declared functions it returns an error like this.
C:\Users\fagel\Documents\Blackjack\Blackjack\CardTest.obj : error LNK2019: unresolved external symbol "public: void __thiscall HandValueCalculator::a(void)" (?a#HandValueCalculator##QAEXXZ) referenced in function "void __cdecl Test(void)" (?Test##YAXXZ)
Your HandValueCalculator does not have a void a(); implementation available to the linker. If the a function is defined, make sure you link with the object file containing the definition.
However, you're most likely the victim of the most vexing parse and think you've declared a to be a variable (somewhere not shown), but you've instead declared a function (without definition).
Noobie programmer here learning C++ for the first time. The following is excerpted code from Teach Yourself C++ 3rd Edition.
I'm dying help me, I'm learning about classes, but I can't get this code to compile on visual studio or on Code::Blocks. :(
//#include "stdafx.h"
#include <iostream>
//I understand this. Headers, etc.
using namespace std;
//and this, name traffic management system
class myclass {
//private to myclass
int a;
public:
void set_a(int num);
int get_a();
};
/*I understand int a is private/inaccessible from the rest of the code
and void set_a(int num) is the dummy function.*/
void myclass::set_a(int num)
//not sure what this is
{
a = num;
}
/*self explanatory*/
int _tmain(int argc, _TCHAR* argv[])
{
myclass ob1, ob2;
ob1.set_a(10);
ob2.set_a(99);
cout << ob1.get_a() << "\n";
cout << ob2.get_a() << "\n";
return -5;
}
/*This is just supposed to output the number 10 and 99 right?? So why isn't it?*/
On Visual Studio the full error description is:
Error 1 error LNK2019: unresolved external symbol "public: int __thiscall myclass::get_a(void)" (?get_a#myclass##QAEHXZ) referenced in function _wmain c:\Users\bernardo pliego\documents\visual studio 2013\Projects\Chapter 1.5\Chapter 1.5\Chapter 1.5.obj Chapter 1.5
On Code::Blocks I receive the following error:
In function 'main':
undefined reference to 'my_class::get_a()'
I am in dire need of help, can someone explain this to me?
Because you don't define get_a, you only declare it. Add a definition like this:
int myclass::get_a() { return a; }
Or just define it inline:
class myclass {
//private to myclass
int a;
public:
void set_a(int num);
int get_a() { return a };
};
You don't ever define int get_a(); so you get an error at link-time.
Include this just above your (rather hubristic) /*self explanatory*/ comment
int myclass::get_a()
{
return a;
}
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Why can templates only be implemented in the header file?
Main class
int main() {
initCarList();
}
void initCarList() {
List<Car> carList;
Car c1 = Car("Toyota", "Bettle", 5);
carList.add(c1);
Car c2 = Car("Mercedes", "Bettle", 7);
carList.add(c2);
Car c3 = Car("FireTruck", "Large Van", 20);
carList.add(c3);
Car c4 = Car("Puma", "Saloon Car", 10);
carList.add(c4);
}
List class
#include "List.h"
#include <iostream>
using namespace std;
template <typename ItemType>
class List {
private:
ItemType itemList[10];
int size;
public:
List();
void add(ItemType);
void del(int index);
bool isEmpty();
ItemType get(int);
int length();
};
template<typename ItemType>
List<ItemType>::List() {
size = 0;
}
template<typename ItemType>
void List<ItemType>::add(ItemType item) {
if(size < MAX_SIZE) {
itemList[size] = item;
size++;
} else {
cout << typename << " list is full.\n";
}
}
I got errors like these
Error 3 error LNK2019: unresolved external symbol "public: void
__thiscall List::add(class Car)" (?add#?$List#VCar####QAEXVCar###Z) referenced in function "void
__cdecl initCarList(void)" (?initCarList##YAXXZ) C:\Users\USER\Desktop\New
folder\DSA_Assignment\main.obj DSA_Assignment
Did I do anything wrongly in my code? NEED HELP THANKS!
There is a syntax error (cout << typename ) in your code. I don't know how you got the linker error. May be its not being compiled at all.
otherwise its okay http://ideone.com/PGWGZu
Clearly you did as it doesn't work! Flippancy aside, let's take a look at the error message bit by bit:
Error 3 error LNK2019: unresolved external symbol
So this is a linkage error. The linker is trying to put together the units that were individually compiled together, but in this case it can't find an external symbol - usually a function or variable name.
"public: void __thiscall List::add(class Worker)" (?add#?$List#VWorker####QAEXVWorker###Z)
This is the full signature of the function that you're missing. It's name manged unfortunately but with your context knowledge of the code that you're writing, you should be able to tell that it's:
void List::add(Worker)
The next bit ...
referenced in function "void __cdecl initWorkerList(void)" (?initWorkerList##YAXXZ) C:\Users\USER\Desktop\New folder\DSA_Assignment\main.obj DSA_Assignment
... is telling you where the problem is happening, i.e where in the code it's trying to link, there is a reference to the missing function. Again, after demangling it's in:
void initWorkerList()
As you can see, with a bit of graft, you can determine exactly what you've done wrong here. Hope this helps.
I'm working on a assignment for class so this is only part of the code, but whenever I try to compile it I'm getting this error.
1>pass9.obj : error LNK2019: unresolved external symbol "void __cdecl bestbuy(double,double,double)" (?bestbuy##YAXNNN#Z) referenced in function _main
1>C:\Users\YoggieBear\Desktop\school\pass9\Debug\pass9.exe : fatal error LNK1120: 1 unresolved externals
Code is below
#include <iostream>
using namespace std;
void bestbuy(double, double, double);
void discountresults (double, double);
void howmany(double, double);
int price1, price2, price3;
int main ()
{
cout<<"Please enter 3 prices.\n";//This tests function bestbuy.
cin>>price1>>price2>>price3;
bestbuy(price1,price2,price3);
cout<<"Your lowest price entered was "<<price1<<" and it was the "<<price2<<" number you entered.\n";
system ("PAUSE");
return 0;
}
void bestbuy(double &val1,double &val2, double val3)
{
if (val1 < val2 && val1 < val3)
val2 = 1;
else if (val2 < val1 && val2 < val3)
{val1 = val2;
val2 = 2;}
else
{val1 = val3;
val2 = 3;}
}
Your function declaration does not match your function definition.
Update it as below:
void bestbuy(double&, double&, double);
Your forward declaration is
void bestbuy(double, double, double);
And your attempt at definition is
void bestbuy(double &val1,double &val2, double val3)
They are clearly referring to two different functions. Both signatures have to match, either drop the references or add them to the forward declaration as well. What you are doing right now is forward declaring a function and defining an overload for that non defined function.
You're declaring the function as taking values, but define it as taking references. Change the declaration to void bestbuy(double&, double&, double);.