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Jul 22nd, 2005

save self-defined object in vector problem

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I define a class which hold some variables first:

C++ Syntax (Toggle Plain Text)
class Command{
	string cHandle;			
	int numPara;
	vector<int> cPara;		
public:
	Command();
	Command(string ucData);
        //...............more functions here	
}; //end of class definition
class Command{
	string cHandle;			
	int numPara;
	vector<int> cPara;		
public:
	Command();
	Command(string ucData);
        //...............more functions here	
}; //end of class definition

Then I declare an object of Command and wanna store it in a vector

C++ Syntax (Toggle Plain Text)
vector<Command> cv;
Command c;
//... some operation of c, tested ok
cv.push_back(c);                                    //segmentation fault here
vector<Command> cv;
Command c;
//... some operation of c, tested ok
cv.push_back(c);                                    //segmentation fault here

The thing is if I only initial c.cHandle, everything ok
if I initial both c.cHandle and c.cPara[ ]
I got a segmentation fault at the last line
what could be my mistake? thanks.

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alone2005

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Jul 22nd, 2005

Re: save self-defined object in vector problem

I kind figure out where is the problem, cause I wrote a copy constructor in Command class
if I comment this function out, everything in peace

C++ Syntax (Toggle Plain Text)
Command::Command(const Command& c){ 
	cHandle=c.getHandle();
	numPara=c.getNumPara();
	for(int i=0;i<numPara;i++) cPara[i]=c.getPara(i);
}
Command::Command(const Command& c){ 
	cHandle=c.getHandle();
	numPara=c.getNumPara();
	for(int i=0;i<numPara;i++) cPara[i]=c.getPara(i);
}

But now I am even more confused, cause this function is only defined but has never been
used, how could it cause a memory fault? help pls?

alone2005

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Jul 22nd, 2005

Re: save self-defined object in vector problem

Quote originally posted by alone2005 ...

But now I am even more confused, cause this function is only defined but has never been used, how could it cause a memory fault? help pls?

As usual, the answer is probably in the code that you haven't show. Try paring the code down to a minimum that demonstrates the problem, but is yet fully compileable as-is. Then we can provide real answers. Otherwise we play 20 questions until you randomly post the problem spot. As a bonus, you may receive advice on how to better other unrelated portions of your code.

Dave Sinkula

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long time no c

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Jul 22nd, 2005

Re: save self-defined object in vector problem

Quote originally posted by Dave Sinkula ...

As usual, the answer is probably in the code that you haven't show. Try paring the code down to a minimum that demonstrates the problem, but is yet fully compileable as-is. Then we can provide real answers. Otherwise we play 20 questions until you randomly post the problem spot. As a bonus, you may receive advice on how to better other unrelated portions of your code.

Sorry i didn't post the full code only because it involve too much other classes, I will try to make a compilable short version here: 3 files, Command.h, Command.cpp, test.cpp

C++ Syntax (Toggle Plain Text)
#ifndef _USER_COMMAND_
#define _USER_COMMAND_
 
#include <string>
#include <vector>
#include <iostream>
 
using namespace std;
 
class UserCommand{
	string cHandle;			//definition of command
	int numPara;
	vector<int> cPara;		//parameter of command
public:
	UserCommand();
	UserCommand(string ucData);
	//copy constructor
	UserCommand(const UserCommand& uc);
 
	void commandParser(string ucData);
	inline string getHandle() const {return cHandle;}
	inline int getPara(int i)const {return cPara[i];}
	inline int getNumPara() const {return numPara;}
}; //end of class definition
#endif
#ifndef _USER_COMMAND_
#define _USER_COMMAND_

#include <string>
#include <vector>
#include <iostream>

using namespace std;

class UserCommand{
	string cHandle;			//definition of command
	int numPara;
	vector<int> cPara;		//parameter of command
public:
	UserCommand();
	UserCommand(string ucData);
	//copy constructor
	UserCommand(const UserCommand& uc);
	
	void commandParser(string ucData);
	inline string getHandle() const {return cHandle;}
	inline int getPara(int i)const {return cPara[i];}
	inline int getNumPara() const {return numPara;}
}; //end of class definition
#endif

C++ Syntax (Toggle Plain Text)
#include "Command.h" 
 
using namespace std;
 
UserCommand::UserCommand():cHandle(""), numPara(0) { }
 
UserCommand::UserCommand(string ucData):cHandle(""), numPara(0){ 
	commandParser(ucData);	
}
 
//Copy constructor
UserCommand::UserCommand(const UserCommand& ucc){ 
	cHandle=ucc.cHandle;
	numPara=ucc.numPara;
	for(int i=0;i<ucc.numPara;i++) cPara[i] = ucc.cPara[i];
}
 
void UserCommand::commandParser(string ucData){
//in fact this function will extract para from string, now just make it simple
        cHandle="handle";
        numPara=5;
	for(int i=0; i<5; i++)	cPara.push_back(i);
}
#include "Command.h" 

using namespace std;

UserCommand::UserCommand():cHandle(""), numPara(0) { }

UserCommand::UserCommand(string ucData):cHandle(""), numPara(0){ 
	commandParser(ucData);	
}

//Copy constructor
UserCommand::UserCommand(const UserCommand& ucc){ 
	cHandle=ucc.cHandle;
	numPara=ucc.numPara;
	for(int i=0;i<ucc.numPara;i++) cPara[i] = ucc.cPara[i];
}

void UserCommand::commandParser(string ucData){
//in fact this function will extract para from string, now just make it simple
        cHandle="handle";
        numPara=5;
	for(int i=0; i<5; i++)	cPara.push_back(i);
}

C++ Syntax (Toggle Plain Text)
 
#include "Command.h"
 
using namespace std;
 
int main(){
	UserCommand uc;
	vector<UserCommand> ucv;
 
        string input=" ";     
	uc.commandParser(input);
	ucv.push_back(uc);                //segmentation fault here
 
	return 0;
}
#include "Command.h"

using namespace std;

int main(){
	UserCommand uc;
	vector<UserCommand> ucv;

        string input=" ";     
	uc.commandParser(input);
	ucv.push_back(uc);                //segmentation fault here

	return 0;
}

After long debug I found that if I delete the copy constructor, it will work.
Or if I don't delelte cc, then only initialize <cHandle> in UserCommand::commandParser( ) method and leave <cPara> empty, it will work too. So I must have some missing
knowledge about copy constructor?

alone2005

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