Error on line -1? - c++

Question

I have a class called PID. I #include the header for the class. I have been using this class in various files including the file the error points to. The compiler complains about defining the function declaration itself void dispPid(char *name, PID &pid){}. All the contents of the function are commented out. The error reads AutoTrucker:-1: error: 'PID' has not been declared with no other errors. Commenting out the function in its entirety removes the error completely, compiles and works fine.
What really gets me confused is that:
The error points to line -1
The file exists, and is included
I use this PID class in right above as a pointer:
PID *pid;
if (chk(arg2,"roll")){pid = &aircraft.ap.pid.wingLeveler;}
else if (chk(arg2,"heading") || chk(arg2,"hdg")){pid = &aircraft.ap.pid.headingHold;}
else if (chk(arg2,"pitch")){pid = &aircraft.ap.pid.pitchHold;}
...
This code specified directly above compiles and works properly. So what gives?
EDIT 2:
This is such a jimmy rig it makes me sick. But is does solve the problem for the time being. So what gives? The compiler does not like the PID class as a function argument, but it finds it acceptable inside the function? I would really like to find a proper solution to this instead of passing in a void pointer and converting it!
void dispPid(const char *name, void *tpid)
{
PID &pid = *((PID*)tpid);
...
}
EDIT: (adding in some more source code as requested)
void cmdsPid(char *buffer)
{
if (chk(buffer,"pid"))
{
char *arg1 = next(buffer);
if (chk(arg1,"ls"))
{
char *arg2 = next(arg1);
if (chk(arg2,"") || chk(arg2,"all"))
{
/*
Serial.println("Listing all PIDs:");
dispPid("Roll",aircraft.ap.pid.wingLeveler);
Serial.print("\t");
dispPid("Heading",aircraft.ap.pid,headingHold);
dispPid("Pitch",aircraft.ap.pid,pitchHold);
Serial.print("\t");
dispPid("V-Rate",aircraft.ap.pid.climbHold);
Serial.print("\t\t");
dispPid("Altitude",aircraft.ap.pid.altHold);
dispPid("Throttle",aircraft.ap.pid.throttleHold);
dispPid("Slip",aircraft.ap.pid.slipHold);
*/
}
else
{
Serial.print("Unknown argument");
}
}
else if (chk(arg1,"w"))
{
char *arg2 = next(arg1);//name
char *arg3 = next(arg2);//attr
char *arg4 = next(arg3);//val
double val = 0.0;
bool onoff = false;
if (chk(arg3,"inv"))
{
onoff = (chk(arg4,"off") || chk(arg4,"-"));
}
else if (chk(arg3,"max") || chk(arg3,"min"))
{
if (chk(arg4,"off") || chk(arg4,"-"))
{
onoff = false;
}
else
{
onoff = true;
val = parseDoubleArg(arg4);
}
}
else
{
val = parseDoubleArg(arg4);
}
PID *pid;
if (chk(arg2,"roll")){pid = &aircraft.ap.pid.wingLeveler;}
else if (chk(arg2,"heading") || chk(arg2,"hdg")){pid = &aircraft.ap.pid.headingHold;}
else if (chk(arg2,"pitch")){pid = &aircraft.ap.pid.pitchHold;}
else if (chk(arg2,"vrate")){pid = &aircraft.ap.pid.climbHold;}
else if (chk(arg2,"alt")){pid = &aircraft.ap.pid.altHold;}
else if (chk(arg2,"th")||chk(arg2,"thr")||chk(arg2,"thro")||chk(arg2,"throttle")){pid = &aircraft.ap.pid.throttleHold;}
else if (chk(arg2,"slip")){pid = &aircraft.ap.pid.slipHold;}
if (chk(arg3,"p")){pid->setPGain(val);}
else if (chk(arg3,"i")){pid->setIGain(val);}
else if (chk(arg4,"d")){pid->setDGain(val);}
else if (chk(arg4,"max"))
{
if (onoff){pid->setLimitMax(val);}
else{pid->disableMaxLimit();}
}
else if (chk(arg4,"min"))
{
if (onoff){pid->setLimitMin(val);}
else{pid->disableMinLimit();}
}
}
else
{
Serial.println("Unknown argument");
}
}
}
void dispPid(char *name, PID &pid){}
The PID class (header):
#pragma once
#define PID_VERSION "1.1"
#include <inttypes.h>
#define allowLimitMax 1
#define allowLimitMin 2
#define invert 4
#define enabled 8
class PID
{
private:
double pGain,iGain,dGain;
double integrator;
double *input,*output,*setpoint;
double lastInput;
double limitMax,limitMin;
char settings;
public:
struct Spid {
double p,i,d,limitMax,limitMin;
char settings;
};
PID();//constructor
//getters
double getPGain();
double getIGain();
double getDGain();
double getLimitMax();
double getLimitMin();
bool isLimitMaxSet();
bool isLimitMinSet();
bool isInverted();
//setters
void setPGain(double newPGain);
void setIGain(double newIGain);
void setDGain(double newDGain);
void setPIDGain(double newPGain, double newIGain, double newDGain);
void setInput(double *newInput);
void setOutput(double *newOutput);
void setSetpoint(double *newSetpoint);
void setIOS(double *newInput, double *newOutput, double *newSetpoint);
void setLimitMax(double newLimitMax);
void setLimitMin(double newLimitMin);
void setLimits(double newLimitMin, double newLimitMax);
void disableMaxLimit();
void disableMinLimit();
void disableLimits();
void zeroOutIntegrator();
void nullOut();
void setInverted(bool newInvert);
//actions
void run();
void run(double dt);
void setFrom(Spid copy);
void copy(Spid &copy);
};