Thanks for resolving some issues I was having. I could fund a small 3rd
world army with what I've spent on books, but sometimes just need to ask
that one question of someone "in the know".
Mitch
> -----Original Message-----
> From: Greg Winton [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, March 10, 1999 2:19 PM
> To: [EMAIL PROTECTED]
> Subject: RE: Variable storage question
>
> At 01:26 PM 3/10/99 -0500, you wrote:
> >If I understand correctly, char s1[]= "Hello"; puts that array of
> characters
> >(plus the NULL) on the stack. Could I then execute something like
> >printf("%s", s1) and have it print Hello? If true, when that printf
> runs,
> >how does it know which bytes to pull off the stack. I might have added
> >additional things to the stack, so how does it know where to find it if
> >there is no pointer to it? If I could understand that, I'd really be
> getting
> >somewhere. Thanks.
>
> Mitch,
>
> This gets into the nature of 'C' arrays; 'C' arrays *are* pointers.
>
> Let's say we have the following declarations:
>
> char s1[] = "Hello";
> char* sP = s1;
>
> sP and s1 are both pointers to the same memory (the 'H'). We can mostly
> use s1 and sP as equivalents:
>
> (*s1) = 'G'; s1 [0] = 'G'; (*sP) = 'G'; sP [0] = 'G';
>
> All these expressions do the exact same thing - they change the first
> letter of the string to 'G'. In the same way, we can say:
>
> *(s1+1) = 'o'; s[1] = 'o'; *(sP+1) = 'o'; sP [1] = '0';
>
> Again, here s1 and sP can both be used as "arrays" or "pointers". We can
> pass s1 to *any* function that takes a string pointer:
>
> StrCopy (s1, "Dog");
> StrCopy (sP, "Cat");
>
> We can even legally do really bad things:
>
> *(s1+20) = '\0'; // This will probably crash the program at some
> point.
> StrCopy (s1, "Goodbye"); // So will this
>
> The only thing we can't do with s1 that we can do with sP is to change
> what
> it points to:
>
> char s2 = "Goodbye";
>
> sP = s2; // this is legal
> s1 = s2; // this is not - the compiler will object.
>
> Effectively, what s1 really represents is a constant pointer to
> non-constant data. The fact that the data is not constant is what causes
> it to be allocated on the stack - the application *must* be able to change
> it. It is the "const-ness" of the data you point to that determines where
> it is stored.
>
> Hope this helps.
>
> Regards,
> Greg
>
>
>
> Greg Winton
> Bachmann Software and Services, LLC
> mailto:[EMAIL PROTECTED]
> http://www.bachmannsoftware.com
> Software Development for Handheld & Mobile Computing, Windows and the
> Internet
> Home of Bachmann Print Manager, the only graphical printing solution for
> the Palm Computing Platform
>
