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3.8

Small newbie C++ app - avoiding memory leaks

Asked by dneill8 in C++ Programming Language, C Programming Language, C# Programming Language

Tags: C++

I've written a small C++ app to employ an API that get distance from two zip codes. Occasionally we need to identify zip codes the tied-to application finds to be invalid. The zip codes are received as arguments to the application I wrote and are concatenated into strings 18 characters long, which are then passed to the function. I'm new to C++ and a lack of garbage collection so, I'm wanting to make sure my understanding of how I employed the string class I wrote (from a book) is correct. The way I understand it, the destructor String::~String() is called whenever the strings, created using the String class, go out of scope. I'm hoping this means that the memory used by the strings initialized at the beginning of main:

String input1, input2, input3, zip1, zip2, zip3, suffix;

is freed when the program exits - when main goes out of scope. Is this correct?
Do I need to worry about the memory taken up by:
long ret_value
and argv[1] and argv[2]
which, as I understand it, are the only other variables I'm employing.

Eventually I hope to learn how to use the leak debugging classes, etc but, at this time, I'm just wanting to get my basic understanding of how to clean up correct.

I'm aware of the need to move from the archaic strcpy and strcat to strcpy_s and strcat_s. The included source below compiles and runs as expected. When I've switched to the current string handling methods, I get problems which I'll address in another question.

TIA

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             #include "stdafx.h"
#include <iostream>
#include <iomanip>
#include <string.h>
#include <fcntl.h>
#include <io.h>
#include "test2.h"
 
// build requires a link to miles32.lib
// in Vis Studio 2005, rclick on Project, Add existing item
// to bring in miles32.lib (should copy the file into the project
// directory
// by same means can Add existing item for test1.h to Header Files
// section
 
using namespace std; 
 
#define NULBYT '\0'
 
char input[200];
char output[4000];
 
class String {
private:
    char *ptr;
public:
    String();
    String(char *s);
    String(const String &src);
    ~String();
 
    String& operator=(const String &src)
        {cpy(src.ptr); return *this;}
 
    String& operator=(char *s)
        {cpy(s); return *this;}
 
    String operator+(char *s);
    int operator==(const String &other);
    operator char*() {return ptr;}
 
    void cat(char *s);
    void cpy(char *s);
};
 
void main(int argc, char *argv[])
{
 
  //LOCATION_RECORD from, *pf;
  //LOCATION_RECORD to, *pt; 
  //LOCATION_RECORD vald, *pv;
  long ret_value;                       
  //pf = &from;
  //pt = &to;                
  //pv = &vald;
 
    String input1, input2, input3, zip1, zip2, zip3, suffix;
    zip1 = argv[1];
    zip2 = argv[2];
	zip3 = "06111";
    suffix = "                 ";
    input1 = zip1 + suffix;
	input2 = zip2 + suffix;
	input3 = zip3 + suffix;
 
  ret_value = GetHHGDistanceValid(input1,input2);
 
  if (ret_value == -1)
  {
	if (GetHHGDistanceValid (input3, input1) == -1) { printf("%s",argv[1]); }
	if (GetHHGDistanceValid (input3, input2) == -1) { printf("%s",argv[2]); }
  } else {
	cout << ret_value;
  }
  ExEnd();                               
}                           
 
// ----------------------------------
// STRING CLASS FUNCTIONS
 
String::String() {
    ptr = new char[1];
    ptr[0] = '\0';
}
 
String::String(char *s) {
    int n = strlen(s);
    ptr = new char[n + 1];
    strcpy(ptr, s);
    //strcpy_s(ptr,strlen(ptr), s);
}
 
String::String(const String &src) {
    int n = strlen(src.ptr);
    ptr = new char[n + 1];
    strcpy(ptr, src.ptr);
    //strcpy_s(ptr,strlen(ptr),src.ptr);
}
 
String::~String() {
    delete [] ptr;
}
 
int String:: operator==(const String &other) {
    return (strcmp(ptr, other.ptr) == 0);
}
 
String String::operator+(char *s) {
    String new_str(ptr);
    new_str.cat(s);
    return new_str;
}
 
// cpy -- Copy string function
//
void String::cpy(char *s) {
    delete [] ptr;
    int n = strlen(s);
    ptr = new char[n + 1];
    strcpy(ptr, s);
    //strcpy_s(ptr,strlen(ptr),s);
}
 
// cat -- Concatenate string function
//
void String::cat(char *s) {
 
    // Allocate sufficient room for new string data.
 
    int n = strlen(ptr) + strlen(s);
    char *p1 = new char[n + 1];
 
    // Copy data to this new memory block.
 
    strcpy(p1, ptr);
    strcat(p1, s);
//    strcpy_s(p1,strlen(p1),ptr);
//// w. strcat_s the 2nd parameter is total length of buffer
//    strcat_s(p1,strlen(p1),s);
 
    // Release old memory block and update ptr.
 
    delete [] ptr;
    ptr = p1;
}

           
         

20091021-EE-VQP-81 / EE_QW_2_20070628

Small newbie C++ app - avoiding memory leaks

Asked by dneill8 in C++ Programming Language, C Programming Language, C# Programming Language

Tags: C++

About this solution