save self-defined object in vector problem

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save self-defined object in vector problem

 
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  #1
Jul 22nd, 2005
I define a class which hold some variables first:
C++ Syntax (Toggle Plain Text) 
  1. class Command{
  2. 	string cHandle;			
  3. 	int numPara;
  4. 	vector<int> cPara;		
  5. public:
  6. 	Command();
  7. 	Command(string ucData);
  8.         //...............more functions here	
  9. }; //end of class definition

Then I declare an object of Command and wanna store it in a vector
C++ Syntax (Toggle Plain Text) 
  1. vector<Command> cv;
  2. Command c;
  3. //... some operation of c, tested ok
  4. 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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Re: save self-defined object in vector problem

 
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  #2
Jul 22nd, 2005
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) 
  1. Command::Command(const Command& c){ 
  2. 	cHandle=c.getHandle();
  3. 	numPara=c.getNumPara();
  4. 	for(int i=0;i<numPara;i++) cPara[i]=c.getPara(i);
  5. }

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?
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Re: save self-defined object in vector problem

 
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  #3
Jul 22nd, 2005
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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.
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand
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Re: save self-defined object in vector problem

 
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  #4
Jul 22nd, 2005
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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) 
  1. #ifndef _USER_COMMAND_
  2. #define _USER_COMMAND_
  3.  
  4. #include <string>
  5. #include <vector>
  6. #include <iostream>
  7.  
  8. using namespace std;
  9.  
  10. class UserCommand{
  11. 	string cHandle;			//definition of command
  12. 	int numPara;
  13. 	vector<int> cPara;		//parameter of command
  14. public:
  15. 	UserCommand();
  16. 	UserCommand(string ucData);
  17. 	//copy constructor
  18. 	UserCommand(const UserCommand& uc);
  19.  
  20. 	void commandParser(string ucData);
  21. 	inline string getHandle() const {return cHandle;}
  22. 	inline int getPara(int i)const {return cPara[i];}
  23. 	inline int getNumPara() const {return numPara;}
  24. }; //end of class definition
  25. #endif

C++ Syntax (Toggle Plain Text) 
  1. #include "Command.h" 
  2.  
  3. using namespace std;
  4.  
  5. UserCommand::UserCommand():cHandle(""), numPara(0) { }
  6.  
  7. UserCommand::UserCommand(string ucData):cHandle(""), numPara(0){ 
  8. 	commandParser(ucData);	
  9. }
  10.  
  11. //Copy constructor
  12. UserCommand::UserCommand(const UserCommand& ucc){ 
  13. 	cHandle=ucc.cHandle;
  14. 	numPara=ucc.numPara;
  15. 	for(int i=0;i<ucc.numPara;i++) cPara[i] = ucc.cPara[i];
  16. }
  17.  
  18. void UserCommand::commandParser(string ucData){
  19. //in fact this function will extract para from string, now just make it simple
  20.         cHandle="handle";
  21.         numPara=5;
  22. 	for(int i=0; i<5; i++)	cPara.push_back(i);
  23. }

C++ Syntax (Toggle Plain Text) 
  1.  
  2. #include "Command.h"
  3.  
  4. using namespace std;
  5.  
  6. int main(){
  7. 	UserCommand uc;
  8. 	vector<UserCommand> ucv;
  9.  
  10.         string input=" ";     
  11. 	uc.commandParser(input);
  12. 	ucv.push_back(uc);                //segmentation fault here
  13.  
  14. 	return 0;
  15. }

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?
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