Programming Forums > Application Development > C++

codenemesis · Nov 9th, 2007, 7:14 PM

I've written code to search, add/remove items from a hashtable. My program compiles without errors, but it crashes with an access violation error(msvcr80d.dll!strcat...). I haven't found any solutions to that particular message, so I've decided to start with the constructors. I'd appreciate any suggestions. I cannot let this code defeat me! My professor tried to help me and finally suggested I see tutors. The tutor tried to help me for several hours and finally suggested the internet.
From stock.h:

(Toggle Plain Text)

 class stock
{
public:
stock(char const * const symbol, char const * const name, int sharePrice, date priceDate);                                          // sharePrice is given as a number of CENTS

stock(const stock& s);		// copy constructor
stock(void);			// default constructor
char const * const getSymbol(void) const;
stock& operator=(const stock& s);
stock& operator=(stock const * const s);
~stock(void);

From stock.cpp:

(Toggle Plain Text)

stock::stock(char const * const symbol, char const * const name, int sharePrice, date priceDate):
    
    sharePrice(sharePrice),
    priceDate(priceDate)
{

    int length = strlen(symbol);
    this -> symbol = new char[length + 1];
    
    strcpy(this -> symbol,symbol);
    length = strlen(name);

    this -> name = new char[length + 1];
    strcpy(this -> name,name);
}

stock::stock(const stock& s):
    
    sharePrice(s.sharePrice),
    priceDate(s.priceDate)
    
	{
    //symbol = new char[strlen(symbol) + 1];
    strcpy(symbol,s.symbol);
    //name = new char[strlen(name) + 1];
    strcpy(name,s.name);
	}


stock& stock::operator=(const stock& s)
    
{
    cout << s.sharePrice;
    priceDate = s.priceDate;
    
    sharePrice = s.sharePrice;
    
	
    symbol = new char[strlen(symbol) + 1];
    strcpy(symbol,s.symbol);
    
    name = new char[strlen(name) + 1];
    strcpy(name,s.name);
    
    return *this;
}

stock& stock::operator=(stock const * const s)
{
    
	return *this;
}

stock::stock():
    symbol(symbol),
    name(name),
    sharePrice(sharePrice),
    priceDate(priceDate)
{
}

grumpy · Nov 10th, 2007, 1:18 AM

In the code you've given, your copy constructor and assignment operators are among the obvious candidate culprits.

The assignment operator will need to be something like this;

(Toggle Plain Text)

stock &stock::operator=(const stock& s):    
 {
    sharePrice = s.sharePrice;
    priceDate = s.priceDate;
    delete [] symbol;
    delete [] name;    // avoid memory leak.  Note:  this assignment operator is not exception safe

    symbol = new char[strlen(s.symbol) + 1];
    strcpy(symbol,s.symbol);
    name = new char[strlen([color="RED"]s./color]name) + 1];
    strcpy(name,s.name);
    return *this;
}

and your copy constructor will, preferably, be something like this;

(Toggle Plain Text)

stock::stock(const stock& s):
    symbol(new char[strlen(s.symbol) + 1]),
    name(new char[strlen(s.name) + 1]),
    sharePrice(s.sharePrice),
    priceDate(s.priceDate)
{
    strcpy(symbol,s.symbol);
    strcpy(name,s.name);
}

The default constructor (the one with no arguments) is also a problem, as the non-static members are uninitialised, and you are using them to initialise themselves. That is formally undefined behaviour. If you really need such a constructor, provide more sensible default values.

It would probably be a good idea to use a std::string, rather than char * members, but that won't help you understand the problem you're having.

Klipt · Nov 10th, 2007, 1:23 AM

What grumpy said (but with an extra '['). Also, is there any point to that last constructor which takes a pointer?

grumpy · Nov 10th, 2007, 2:02 AM

Oh, bugger! One time when I wish to edit my post to make the content clearer, and can't.

codenemesis · Nov 17th, 2007, 6:09 PM

Thanks. After I corrected my constructors and copy consturctors, I was able to see all of my "other" compile errors. One of my copy constructor errors was that I had two copies.
Good times.

Nov 9th, 2007, 7:14 PM	#1
codenemesis Newbie Join Date: Nov 2007 Location: Oregon Posts: 3 Rep Power: 0	Constructor Syntax help I've written code to search, add/remove items from a hashtable. My program compiles without errors, but it crashes with an access violation error(msvcr80d.dll!strcat...). I haven't found any solutions to that particular message, so I've decided to start with the constructors. I'd appreciate any suggestions. I cannot let this code defeat me! My professor tried to help me and finally suggested I see tutors. The tutor tried to help me for several hours and finally suggested the internet. From stock.h: (Toggle Plain Text) class stock { public: stock(char const * const symbol, char const * const name, int sharePrice, date priceDate); // sharePrice is given as a number of CENTS stock(const stock& s); // copy constructor stock(void); // default constructor char const * const getSymbol(void) const; stock& operator=(const stock& s); stock& operator=(stock const * const s); ~stock(void); class stock { public: stock(char const * const symbol, char const * const name, int sharePrice, date priceDate); // sharePrice is given as a number of CENTS stock(const stock& s); // copy constructor stock(void); // default constructor char const * const getSymbol(void) const; stock& operator=(const stock& s); stock& operator=(stock const * const s); ~stock(void); From stock.cpp: (Toggle Plain Text) stock::stock(char const * const symbol, char const * const name, int sharePrice, date priceDate): sharePrice(sharePrice), priceDate(priceDate) { int length = strlen(symbol); this -> symbol = new char[length + 1]; strcpy(this -> symbol,symbol); length = strlen(name); this -> name = new char[length + 1]; strcpy(this -> name,name); } stock::stock(const stock& s): sharePrice(s.sharePrice), priceDate(s.priceDate) { //symbol = new char[strlen(symbol) + 1]; strcpy(symbol,s.symbol); //name = new char[strlen(name) + 1]; strcpy(name,s.name); } stock& stock::operator=(const stock& s) { cout << s.sharePrice; priceDate = s.priceDate; sharePrice = s.sharePrice; symbol = new char[strlen(symbol) + 1]; strcpy(symbol,s.symbol); name = new char[strlen(name) + 1]; strcpy(name,s.name); return this; } stock& stock::operator=(stock const const s) { return this; } stock::stock(): symbol(symbol), name(name), sharePrice(sharePrice), priceDate(priceDate) { } stock::stock(char const const symbol, char const * const name, int sharePrice, date priceDate): sharePrice(sharePrice), priceDate(priceDate) { int length = strlen(symbol); this -> symbol = new char[length + 1]; strcpy(this -> symbol,symbol); length = strlen(name); this -> name = new char[length + 1]; strcpy(this -> name,name); } stock::stock(const stock& s): sharePrice(s.sharePrice), priceDate(s.priceDate) { //symbol = new char[strlen(symbol) + 1]; strcpy(symbol,s.symbol); //name = new char[strlen(name) + 1]; strcpy(name,s.name); } stock& stock::operator=(const stock& s) { cout << s.sharePrice; priceDate = s.priceDate; sharePrice = s.sharePrice; symbol = new char[strlen(symbol) + 1]; strcpy(symbol,s.symbol); name = new char[strlen(name) + 1]; strcpy(name,s.name); return this; } stock& stock::operator=(stock const const s) { return *this; } stock::stock(): symbol(symbol), name(name), sharePrice(sharePrice), priceDate(priceDate) { }

Nov 10th, 2007, 1:18 AM	#2
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	Re: Constructor Syntax help In the code you've given, your copy constructor and assignment operators are among the obvious candidate culprits. The assignment operator will need to be something like this; (Toggle Plain Text) stock &stock::operator=(const stock& s): { sharePrice = s.sharePrice; priceDate = s.priceDate; delete [] symbol; delete [] name; // avoid memory leak. Note: this assignment operator is not exception safe symbol = new char[strlen(s.symbol) + 1]; strcpy(symbol,s.symbol); name = new char[strlen([color="RED"]s./color]name) + 1]; strcpy(name,s.name); return this; } stock &stock::operator=(const stock& s): { sharePrice = s.sharePrice; priceDate = s.priceDate; delete [] symbol; delete [] name; // avoid memory leak. Note: this assignment operator is not exception safe symbol = new char[strlen(s.symbol) + 1]; strcpy(symbol,s.symbol); name = new char[strlen([color="RED"]s./color]name) + 1]; strcpy(name,s.name); return this; } and your copy constructor will, preferably, be something like this; (Toggle Plain Text) stock::stock(const stock& s): symbol(new char[strlen(s.symbol) + 1]), name(new char[strlen(s.name) + 1]), sharePrice(s.sharePrice), priceDate(s.priceDate) { strcpy(symbol,s.symbol); strcpy(name,s.name); } stock::stock(const stock& s): symbol(new char[strlen(s.symbol) + 1]), name(new char[strlen(s.name) + 1]), sharePrice(s.sharePrice), priceDate(s.priceDate) { strcpy(symbol,s.symbol); strcpy(name,s.name); } The default constructor (the one with no arguments) is also a problem, as the non-static members are uninitialised, and you are using them to initialise themselves. That is formally undefined behaviour. If you really need such a constructor, provide more sensible default values. It would probably be a good idea to use a std::string, rather than char * members, but that won't help you understand the problem you're having.

Nov 10th, 2007, 1:23 AM	#3
Klipt Hobbyist Programmer Join Date: Dec 2005 Posts: 118 Rep Power: 0	Re: Constructor Syntax help What grumpy said (but with an extra '['). Also, is there any point to that last constructor which takes a pointer? __________________ Get PLT Scheme\|SB Common Lisp\|Haskell\|wxDev-C++\|Python

Nov 10th, 2007, 2:02 AM	#4
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	Re: Constructor Syntax help Oh, bugger! One time when I wish to edit my post to make the content clearer, and can't.

Nov 17th, 2007, 6:09 PM	#5
codenemesis Newbie Join Date: Nov 2007 Location: Oregon Posts: 3 Rep Power: 0	Re: Constructor Syntax help Thanks. After I corrected my constructors and copy consturctors, I was able to see all of my "other" compile errors. One of my copy constructor errors was that I had two copies. Good times.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Programming Forums > Application Development > C++

Constructor Syntax help