error LNK2019: unresolved external symbol "" referenced in function

Question

Im currently getting the following error when I compile my code:

error LNK2019: unresolved external symbol "public: void __thiscall Agent::printSelf(void)" (?printSelf@Agent@@QAEXXZ) referenced in function "public: void __thiscall World::processMouse(int,int,int,int)" (?processMouse@World@@QAEXHHHH@Z) World.obj

Here is my code

Agent.h:

class Agent
{
public:
    Agent();

void printSelf();

Agent.cpp:

void Agent::printSelf()
{
printf("Agent species=%i\n", species);
for (int i=0;i<mutations.size();i++) {
    cout << mutations[i];
}
}

GLView.cpp:

void GLView::processMouse(int button, int state, int x, int y)
{
if(world->isDebug()) printf("MOUSE EVENT: button=%i state=%i x=%i y=%i\n", button, state, x, y);

if(button==0){
    int wx= (int) ((x-conf::WWIDTH/2)/scalemult-xtranslate);
    int wy= (int) ((y-conf::WHEIGHT/2)/scalemult-ytranslate);

    world->processMouse(button, state, wx, wy);
}

mousex=x; mousey=y;
downb[button]=1-state;
}


void World::processMouse(int button, int state, int x, int y)
{
 if (state==0) {        
     float mind=1e10;
     float mini=-1;
     float d;

     for (int i=0;i<agents.size();i++) {
         d= pow(x-agents[i].pos.x,2)+pow(y-agents[i].pos.y,2);
             if (d<mind) {
                 mind=d;
                 mini=i;
             }
         }
     if (mind<1000) {
         //toggle selection of this agent
         for (int i=0;i<agents.size();i++) {
            if(i!=mini) agents[i].selectflag=false;
         }
         agents[mini].selectflag= !agents[mini].selectflag;
         agents[mini].printSelf();
         setControl(false);
     }
 }

}

Im pretty stumped. I haven't worked on this code in a long time, so im not sure what has changed to cause this. Anyone see anything wrong?

Answer 1

Most likely cause is that you're not linking in the object created from Agent.cpp.

You should check to ensure that it's part of the project and that you're using the correct version, compiled with this current compiler as well (since you state you haven't touched it in a while, it may be that the objects were built with an earlier compiler version, potentially making them incompatible - different name mangling methods, for example).

The first thing to try (once you've established all correct files are in the project) is a full clean-and-build.

On a few other points:

1. The error is occurring in World::processMouse meaning that the source for GLView::processMouse is probably irrelevant.

2. I find your mixing of printf and cout slightly ... disturbing. You should probably avoid printf for serious C++ programming. It works, but it's mostly intended for legacy C support.

Answer 2

Observed same issue in Visual studio 2008. Clean, followed by Rebuild worked for me.