Embedded Strings -- Arrays or pointers?

[Tomás]

When you have compile-time strings like:

"The file is of unknown format."

What kind of variables do you use to store it? At the moment I'm using:

char const str[] = "The file is of unknown format.";

Do some of you use:

const char* const str = "The file is of unknown format.";

-Tomás

[Alf P. Steinbach]

* Tomás:

When you have compile-time strings like:

"The file is of unknown format."

What kind of variables do you use to store it? At the moment I'm using:

char const str[] = "The file is of unknown format.";

Do some of you use:

const char* const str = "The file is of unknown format.";

Perhaps some do, but I think it would be less than smart to discard
information for such raw data, and to write more to do that.

There is also the question of whether to write

std::string const str = "The file is of unknown format";

and at least for one learning the language I think it's a good idea to
use std::string exclusively, and not delve into the realm of pointers
and raw arrays, simply not get _used_ to the low-level features.

However, there are some scenarios where the std::string constant isn't
possible or advisable.

And of course the strings may instead be embedded in some resource data
structure in the program or in a dynamic library, for
internationaliz ation, but that is platform-dependent and tool-dependent
and therefore outside the scope of discussion in this group.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[jesper]

Tomás wrote:

When you have compile-time strings like:

"The file is of unknown format."

What kind of variables do you use to store it? At the moment I'm using:

char const str[] = "The file is of unknown format.";

Do some of you use:

const char* const str = "The file is of unknown format.";

-Tomás

As far as I know there is no diffrence between them.
I might be ignorant as hell. Is exactly the same.
char astr[]="array hello";
char* pstr="pointer hello";

now you have two zeroterminated memory areas and two pointers.

The diffrence is in literals, as below:
char* pstr2={'e','r', 'r','o','r'};//illegal
char astr2[]=pstr;;//illegal
char astr3[]={'e','r','r',' o','r','\0'};//legal
char astr3[]={'e','r','r',' o','r'};//legal, but not a string since no
zero is appended

Strings are represented by arrays, they are not arrays.
/Jesper

[Sharad Kala]

<je****@alphaca sh.se> wrote in message
news:11******** *************@g 47g2000cwa.goog legroups.com...

Tomás wrote:

When you have compile-time strings like:

"The file is of unknown format."

What kind of variables do you use to store it? At the moment I'm using:

char const str[] = "The file is of unknown format.";

Do some of you use:

const char* const str = "The file is of unknown format.";

-Tomás

As far as I know there is no diffrence between them.
I might be ignorant as hell. Is exactly the same.
char astr[]="array hello";
char* pstr="pointer hello";
---
The above two are not same.
pstr[1] = 'a'; // Illegal
astr[1] = 'a'; // Legal

Sharad

[jesper]

Sharad Kala wrote:
---

The above two are not same.
pstr[1] = 'a'; // Illegal
astr[1] = 'a'; // Legal

Sharad

No thats false.
pstr[1] = 'a'; is legal, its not safe, but it is legal.
standard behaviour is
pstr[1] = 'a';
compiles to
*(pstr+(sizeof( *pstr)))='a';

/Jesper

[Alf P. Steinbach]

* je****@alphacas h.se:

Sharad Kala wrote:
---

The above two are not same.
pstr[1] = 'a'; // Illegal
astr[1] = 'a'; // Legal

Sharad

No thats false.
pstr[1] = 'a'; is legal, its not safe, but it is legal.
standard behaviour is
pstr[1] = 'a';
compiles to
*(pstr+(sizeof( *pstr)))='a';

In the context (which you snipped) the assignment is not valid, because
the pointer points to a literal string constant.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Alf P. Steinbach]

* je****@alphacas h.se:

pstr[1] = 'a';
compiles to
*(pstr+(sizeof( *pstr)))='a';

Not in general (and it is the general you're trying to illustrate?).

It "compiles to", in the sense of being equivalent with,

*(pstr+1) = 'a';

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Jacek Dziedzic]

je****@alphacas h.se wrote:

As far as I know there is no diffrence between them.
I might be ignorant as hell. Is exactly the same.
char astr[]="array hello";
char* pstr="pointer hello";

At this moment, yes, you are ignorant as hell.
pstr resides in read-only memory and trying to modify it
is UB, whereas modifying astr is ok.

HTH,
- J.

[jesper]

Alf P. Steinbach wrote:

* je****@alphacas h.se:

pstr[1] = 'a';
compiles to
*(pstr+(sizeof( *pstr)))='a';

Not in general (and it is the general you're trying to illustrate?).

It "compiles to", in the sense of being equivalent with,

*(pstr+1) = 'a';

yes its the general I'm after. And you are misstaken,
because operator+(char* ,int) defines the size of the element.
The code below works fine. (borland, ansicompliant,f orce c++)

class CClass
{
int i[2];
public:
CClass& operator=(int in){i[0]=in;i[1]=in;}
};

int u[]={1,2,3};
CClass c[3];

template <class T>
void MyPoint(T* arg)
{
arg[1]=3;
}
int main() {
MyPoint(u);
MyPoint(c);
}

[jesper]

I will give on the point concerning the const declarations that
I sadly snipped away. Sorry about that. My only excuse is that you used

the variable names astr and pstr which i introduced and did not declare
const.
Sorry.
But I will remain adamant that the Rvalues are the same type. :-)

BTW. this is the first time I have ever seen the syntax:
const char * const str="string";

Does that second const induce the area protection?
And if so, how would I protect an array the same way?