Thread: help on debugging

Originally Posted by matsp

In theory, that would work. I'd probably use char oo[13] instead [13 is long enough for a 32-bit integer].

However, you return 'o', which is a pointer to the oo variable (yes, itoa() returns the string it got as buffer, which is oo), so you will still return a pointer to a local variable, which is bad. You either should pass a character array to the function, or call malloc() to get a permanent piece of memory (just make sure you free it later).

--
Mats

tanx dear Mats, but when i did

Code:

              char  oo[13];
                        char * o;
                        o = (char*) malloc (13);
                        if (o==NULL) exit (1);

                        o = itoa(temp,oo,8);    //itoa(number,a buffer to hold the string,the base you want the number to be saved in buffer)
                        offsetptr = o;//itoa(temp,ptr,8);    //itoa(number,a buffer to hold the string,the base you want the number to be saved in buffer)
                        free (o);

it didnt work. it just even corrupts the output! i used to get before changing this !

Originally Posted by rags_to_riches

You know, this code is full of char * (C-style strings) usage. Sorry, but if you don't know how to use them, you're destined to fail. This looks like a complicated project to undertake if you don't understand such a rudimentary part of C & C++ programming. If you're used to using the C++ string class and its relatives, then I would use those instead.

yeah , that why i asked for your help!

Why are you refusing to use std::string and standard containers? Read Stroustrup's answer to the FAQ: How do I deal with memory leaks?

Oh, and what's with o and oo? Read Stroustrup's answer to the FAQ: How do you name variables?

Originally Posted by laserlight

Why are you refusing to use std::string and standard containers? Read Stroustrup's answer to the FAQ: How do I deal with memory leaks?

Oh, and what's with o and oo? Read Stroustrup's answer to the FAQ: How do you name variables?

tanx, i am using standard container!! and im using strings! too, i cant use std::string because of the conversions i have to deal with . atoi() only accepts C style strings , or and also itoa() . thats my worst luck ever!

and about o and oo, i used them temporarily just to make that itoa() function to work, i was just testing , and just it happend and it worked, after that , i didnt change them !! ok , ill change their name,

and after all , do i get these errors because i do have a memory leak or sth in my program !! ?
by the way , when i used

Code:

cstr = new char [str.size()+1]; 
  strcpy (cstr, str.c_str());

in my program , ( more than 20 times)
i didnt write "delete[] cstr;" after using them , is it importatn to do so ? i mean could it be the cause to crash ? !!?

and why do i get that error in malloc? what did i do wrong?

Originally Posted by Masterx

tanx, i am using standard container!! and im using strings! too, i cant use std::string because of the conversions i have to deal with . atoi() only accepts C style strings , or and also itoa() . thats my worst luck ever!

Look at it from another perspective: you can't use atoi() because it only accepts C style strings (but then you can get an unmodifiable C style string from a std::string, so that is not entirely true), and you can't use itoa() because it produces a C style string (aside from the fact that it is non-standard).

I believe we have mentioned this before, but the solution is to use a stringstream, or if you are willing to use a non-standard component, then you can use boost::lexical_cast.

Originally Posted by Masterx

and after all , do i get these errors because i do have a memory leak or sth in my program !! ?

They are probably more likely due to an attempt to access memory that you do not own.

Originally Posted by Masterx

i didnt write "delete[] cstr;" after using them , is it importatn to do so ? i mean could it be the cause to crash ? !!?

It is good practice to do so, but it is even better practice to use a class that manages memory for you.

im going to use string stream instead of itoa(). wish me luck .
.please sb tell me if im wrong .

Code:

#include <iostream>
#include <sstream>

int main() {
  int number = 123;

  std::stringstream ss;
  ss << number;

  std::cout << ss.str() << endl;
}

we have an integer number. and we want to convert it to a string ! so we use ss<<number; to copy the number value to ss , . now whats the ss.str()? can i simply write
std:ffset = std::ss now?
will it work?

Originally Posted by Masterx

tanx, i am using standard container!! and im using strings! too, i cant use std::string because of the conversions i have to deal with . atoi() only accepts C style strings , or and also itoa() . thats my worst luck ever!

atoi DOES work with std::string:
But it accepts C-style strings, so use the c_str() member function to get a C-style string from a std::string object.
itoa is non-standard, so it should not be used anyway.
But better yet, get rid of both atoi and itoa and use boost::lexical_cast. It will serve the purpose of both - and more!

and after all , do i get these errors because i do have a memory leak or sth in my program !! ?
by the way , when i used

Code:

cstr = new char [str.size()+1]; 
  strcpy (cstr, str.c_str());

in my program , ( more than 20 times)
i didnt write "delete[] cstr;" after using them , is it importatn to do so ? i mean could it be the cause to crash ? !!?

Of course you must! Otherwise there will be a memory leak!
But you should not do it in the first place (using dynamic memory with new).

and why do i get that error in malloc? what did i do wrong?

malloc should not be used in C++, either. If you need to use dynamic memory, use std::vector. In rare cases where it will not do, use new.

Originally Posted by Elysia

atoi DOES work with std::string:
But it accepts C-style strings, so use the c_str() member function to get a C-style string from a std::string object.
itoa is non-standard, so it should not be used anyway.
But better yet, get rid of both atoi and itoa and use boost::lexical_cast. It will serve the purpose of both - and more!


Of course you must! Otherwise there will be a memory leak!
But you should not do it in the first place (using dynamic memory with new).


malloc should not be used in C++, either. If you need to use dynamic memory, use std::vector. In rare cases where it will not do, use new.

first of all tanx . but second .im really dieing !!!im owerhelmed ! i learn one thing , another just pops up!
well, when trying to use string stream , i encountered a problem !

Code:

|80|error: ambiguous overload for 'operator=' in 'offsetptr = ss'|

edited : i used offsetptr = ss.str(); and voila it works ! i successfully took a step ahead .! thank GOD. and thank you guys too, !
when i tried to std:ffsetptr = ss;!
any reason!

and third : boost::lexical_cast, how should i know if i have it ! if i dont where can i get it ! ?

and at last ,im trying to remove any C style string that i used, let me see if i can do such a thing at my current stage !!

Boost.org
whatever_type_I_want var = boost::lexical_cast<whatever_type_I_want>(source);
Just remember that it throws.

Originally Posted by tabstop

You use >> to get something out of a stringstream.

tanx .dear tabstop. and Oh , GOD i cant believe it , it just wiped out one of the most recent annoying errors i used to get!! i mean this one( #8) is solved now .
im going to change all of the C based stuff now. to see if the errors will be gone !

Code:

              char  oo[13];
                        char * o;
                        o = (char*) malloc (13);
                        if (o==NULL) exit (1);

                        o = itoa(temp,oo,8);    //itoa(number,a buffer to hold the string,the base you want the number to be saved in buffer)
                        offsetptr = o;//itoa(temp,ptr,8);    //itoa(number,a buffer to hold the string,the base you want the number to be saved in buffer)
                        free (o);

There are so many things wrong with this code that I hardly know where to start.
First of all, itoa() returns a pointer to the same address as the input buffer (oo). So, you must not malloc() o, and then assign it with the return from itoa() - it's the same as assigning o = oo after malloc. Then you set offsetptr to o, followed by free(o) - so what memory [assuming the other stuff wasn't all wrong] is o pointing to? Who owns it?

Yes, you must free memory allocated by malloc, but NOT UNTIL YOU HAVE FINISHED USING IT!

Now, it looks like you are planning to use C++ style strings, so it's a moot point anyways, but you it really seems like you need to learn a bit more about the basics of memory and how you deal with it before you start on a complex programming project.

--
Mats

tanx dear mats, in this case i would appreciate a proper and yet sample demosntrating how to use malloc() just for learning purposes, im not gona use it anymore.

and the rest :
ive disabled all of the C string variables so far , and used their equivalent C++ counter parts ,(str::string) .
i even managed to replace the atoi() with the new string stream based Atoi() function i modified :

Code:

#include <cstdlib>
#include <iostream>
#include <sstream>
using namespace std;

int Atoi(string input)
{
        int temp;
    	stringstream ss( input);
    	ss>>temp;
    	return temp;
}

it was primarily accepting a char * as an argumnet , but i changed it into string ! i dont know whether this makes an error or not !, so please tell me about this too.

and now, im having a slight big problem using stringstream in converting octal to decimal. the problem is i dont know , how im supposed to make the string stream understand that , it should treat the number a octal not decimal as default!
well conversion from decimal to octal is fine , because it treats the number as decimal at first ( as the number itself is decimal indeed!)
but when i have an octal number, how can i do this ? i mean simply doing :

Code:

#include <cstdlib>
#include <iostream>
#include <sstream>
using namespace std;

int main(int argc, char *argv[])
{
    
    int num = 12;


    std::stringstream stream;
    stream <<dec<<num;
    std::cout << stream.str();
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

wont give me a correct answer though!
but this program is just fine with stream<<oct<<num, meaning the conversion from decimal to octal.! so im stuck in it !

and by the way , is not a function for converting octal to binary just like the above ! ?
im asking these, because im revising my whole project ! so i do change the functions , and im trying to use standard stuff at first.

( i cant download boost library, im using Dialup now, so , please help me with these stuff. tanx .
-------------------------
logs:
replaced itoa() with a better equivalent by string stream
replace atoi() with a stringstream based function . (Atoi(). i)
replaced all of C style string variables with their std::string counterparts.
DectoOctal() is removed and instead the new function :

Code:

string DectoOct(int dec)
{
    std::stringstream stream;
    stream <<std::oct<<dec;
    return stream.str();

}

is used.
meanwhile im seeking a better function for Octal to bin
the current function i have for cotal to binary conversion is :

Code:

string OcttoBin(int n)
{


         int a[6],i=0,t=0,num;
         string str,str1,str2,message;

         char buffer[9];

         string str_array[9];
         const size_t str_array_size = sizeof(str_array) / sizeof(str_array[0]);

         while(n!=0)
         {
                 a[i]=n%10;
                 n=n/10;
                 if(a[i]>7)
                 t=1;
                 i++;
         }
         i--;
         if(t==0)
          for(;i>=0;i--)
          {
                  switch(a[i])
                   {
                           case 0:
                           if (!str.empty())
                           str.append("000");
                           else
                           str="000";
                           break;

                           case 1:
                           if (!str.empty())
                           str.append("001");
                           else
                           str="001";
                           break;

                           case 2:
                           if (!str.empty())
                           str.append("010");
                           else
                           str="010";
                           break;

                           case 3:
                           if (!str.empty())
                           str.append("011");
                           else
                           str="011";
                           break;

                           case 4:
                           if (!str.empty())
                           str.append("100");
                           else
                           str="100";
                           break;

                           case 5:
                           if (!str.empty())
                           str.append("101");
                           else
                           str="101";
                           break;

                           case 6:
                           if (!str.empty())
                           str.append("110");
                           else
                           str="110";
                           break;

                           case 7:
                           if (!str.empty())
                           str.append("111");
                           else
                           str="111";
                           break;
                   }
          }
          str1="000000";
          str2="000";
              if (str.length()==3)
              {
                        str1.append(str);
                        str=str1;
              }

              if (str.length()==6)
              {
                        str2.append(str);
                        str=str2;
              }



         if(t==1)
          {

                  message="no";
                // cout<<"Not a Octal number\n";
                 return s;
          }

return str;
}

and the last one is to find a way to get stringstream to work properly as i said above.

your problem not in the stringstream

int num = 12;

12 is decimal constant - so you already have a decimal 12 in your var when starting using the stringstream and it is late to recognize 12 as oct or hex

change that line to
int num = 0x12;
for example to represent 12 as hex number

Originally Posted by vart

your problem not in the stringstream

int num = 12;

12 is decimal constant - so you already have a decimal 12 in your var when starting using the stringstream and it is late to recognize 12 as oct or hex

change that line to
int num = 0x12;
for example to represent 12 as hex number

well , tanx, but how am i supposed to do such a thing , when i have a variable that gets its value form some other calculations! and its not just that simple!
e.g suppose " num " has an octal value inside it(e.g 12 is octal here and it = 10 decimal!)! , so in this case , im asking for help!because i cant just add O before the number to imply its octal! so how to convert it now ! how to let the function understand its dealing with an octal integer!?

and any suggestion about octal to binary conversion?