Programming Forums > Application Development > C++

Jabo · Mar 24th, 2008, 10:33 AM

Declared variables:

 c++ Syntax (Toggle Plain Text) 
char d='x';
char e='y';
char f='z';
char d='x';
char e='y';
char f='z';

printed to command line:

 c++ Syntax (Toggle Plain Text) 
int main()
{
     cout<<"value of d = "<< d <<" Address of d = "<< &d <<" size of d= "<< sizeof(d) << endl;
     cout<<"value of e = "<< e <<" Address of e = "<< &e <<" size of e= "<< sizeof(e) << endl;
     cout<<"value of f = "<< f <<" Address of f = "<< &f <<" size of f= "<< sizeof(f) << endl;
return 0;
}
int main()
{
     cout<<"value of d = "<< d <<" Address of d = "<< &d <<" size of d= "<< sizeof(d) << endl;
     cout<<"value of e = "<< e <<" Address of e = "<< &e <<" size of e= "<< sizeof(e) << endl;
     cout<<"value of f = "<< f <<" Address of f = "<< &f <<" size of f= "<< sizeof(f) << endl;
return 0;
}

and I get the following (garbage?)

commandline Syntax (Toggle Plain Text)

value of d = x Address of d = x��*��*��*��*��*��*��*��* size of d = 1
value of e = y Address of e = y��*��*��*��*��*��*��*��*��*��*��*x��*��*��*��*��*��*��*��* size of e = 1
value of f = z Address of f = z��*��*��*��*��*��*��*��*��*��*��*y��*��*��*��*��*��*��*��*��*��*��*x��*��*��*��*��*��*��*��* size of f = 1
Press any key to continue . . .

this doesn't look like valid address notation to me, has anybody seen this before? This is on Vista 64 and it doesn't show as the squares in the command line, but looks like the screen shot below.

Can anybody tell me why the address for e and f include the previous addresses and all the junk?

Jabo · Mar 24th, 2008, 10:36 AM

If I had to guess, I'd say it's because it still allocates a byte for the chars, that's where the junk comes from, but wouldn't it still have a normal memory address? This is confusing.

Jimbo · Mar 24th, 2008, 10:50 AM

If I had to guess, I'd say the way to handle the addresses is ambiguous. You're basically giving cout a char* to print out, and you want the int value, but it's probably looking at it as a null-terminated string. Try casting the addresses to int and see what you get

lectricpharaoh · Mar 24th, 2008, 4:06 PM

Quote:

Originally Posted by Jimbo

If I had to guess, I'd say the way to handle the addresses is ambiguous. You're basically giving cout a char* to print out, and you want the int value, but it's probably looking at it as a null-terminated string. Try casting the addresses to int and see what you get

Jimbo is correct, except for the casting to int part (sizeof(int) and sizeof(char *) are not necessarily equal). When you pass it the address of a char, it receives a char *, and has no way of knowing you want to print the address, rather than a string. Remember that a C-style string, used in C++ as well, is just a series of zero or more char elements, followed by a char with the value zero to act as a terminator. Try something like this instead:

 C++ Syntax (Toggle Plain Text) 
int main(void)
{
  char d = 'x';
  std::cout << "value of d = " << d << " Address of d = "
            << (void *)&d << " size of d = " << sizeof(d)
            << std::endl;
  // repeat for the others
}
int main(void)
{
  char d = 'x';
  std::cout << "value of d = " << d << " Address of d = "
            << (void *)&d << " size of d = " << sizeof(d)
            << std::endl;
  // repeat for the others
}

Jabo · Mar 24th, 2008, 8:59 PM

Thanks guys, I will digest this a bit and see if it can make sense to my old head.

Mar 24th, 2008, 10:36 AM	#2
Jabo Not a user? Join Date: Sep 2007 Posts: 308 Rep Power: 2	Re: Char memory address? If I had to guess, I'd say it's because it still allocates a byte for the chars, that's where the junk comes from, but wouldn't it still have a normal memory address? This is confusing.

Mar 24th, 2008, 10:50 AM	#3
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 770 Rep Power: 3	Re: Char memory address? If I had to guess, I'd say the way to handle the addresses is ambiguous. You're basically giving cout a char* to print out, and you want the int value, but it's probably looking at it as a null-terminated string. Try casting the addresses to int and see what you get __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

Mar 24th, 2008, 8:59 PM	#5
Jabo Not a user? Join Date: Sep 2007 Posts: 308 Rep Power: 2	Re: Char memory address? Thanks guys, I will digest this a bit and see if it can make sense to my old head.

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Programming Forums > Application Development > C++

Char memory address?