String constant

[tech]

Hi, I need to define some strings in a header file, they are to be
const
Whats the best to choose from below;

const std::string s = "Hello";
const char* s = "Hello";
char* s = "Hello";

Thanks

[anon]

tech wrote:

Hi, I need to define some strings in a header file, they are to be
const
Whats the best to choose from below;

const std::string s = "Hello";
const char* s = "Hello";
char* s = "Hello";

Thanks

I am doing one of two:
const std::string s1 = "Hello";
const char* const s2 = "Hello";

[James Kanze]

On Jun 6, 4:02 pm, anon <[e-mail]:

tech wrote:

Hi, I need to define some strings in a header file, they are
to be const Whats the best to choose from below;

const std::string s = "Hello";
const char* s = "Hello";
char* s = "Hello";

I am doing one of two:
const std::string s1 = "Hello";
const char* const s2 = "Hello";

Why the pointer?

--
James Kanze (GABI Software) email:ja*********@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

[Daniel Pitts]

anon wrote:

tech wrote:

>Hi, I need to define some strings in a header file, they are to be
const
Whats the best to choose from below;

const std::string s = "Hello";
const char* s = "Hello";
char* s = "Hello";

Thanks

I am doing one of two:
const std::string s1 = "Hello";
const char* const s2 = "Hello";

Right, don't forget both the const's if you use char *
You want a constant pointer to a constant value.

Depending on your typical use, I would suggest const std::string, since
string adds so much utility.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

[Ian Collins]

tech wrote:

Hi, I need to define some strings in a header file, they are to be
const
Whats the best to choose from below;

const std::string s = "Hello";

This is the only version here than can go in a header.

const char* s = "Hello";

This has to be

const char* const s = "Hello";

Which you use depends on how you use them. If you wish to add to one
later (say it's a root file path), use std::string. If they are
discrete tokens, const char* const can be used. But do bear in mind a
std::string will be constructed each tome you pass one to a function
with a const std::string reference parameter.
--
Ian Collins.

[Ian Collins]

James Kanze wrote:

On Jun 7, 11:27 pm, Ian Collins <[e-mail]:

>tech wrote:

>>const char* s = "Hello";

>This has to be

>const char* const s = "Hello";

Again: what's wrong with:

char cosnt s[] = "Hello" ;

It won't compile?

? Why do you need the extra pointer.

No particular reason, just habit. I'm just used to thinking of a
constant pointer to a string literal. A string literal has to have an
address, so where's the extra pointer?

--
Ian Collins.

[Frank Birbacher]

Hi!

Ian Collins schrieb:

No particular reason, just habit. I'm just used to thinking of a
constant pointer to a string literal. A string literal has to have an
address, so where's the extra pointer?

The pointer itself also has an address. It's one address more than the
array solution has. The array solution saves sizeof(char*) bytes (or
whatever) in the resulting object file (or it is optimized away).

Frank

[Ian Collins]

Frank Birbacher wrote:

Hi!

Ian Collins schrieb:

>No particular reason, just habit. I'm just used to thinking of a
constant pointer to a string literal. A string literal has to have an
address, so where's the extra pointer?

The pointer itself also has an address. It's one address more than the
array solution has. The array solution saves sizeof(char*) bytes (or
whatever) in the resulting object file (or it is optimized away).

That was my point, it will more then likely be optimised away.

--
Ian Collins.

[James Kanze]

On Jun 8, 12:35 pm, Ian Collins <[e-mail]:

Frank Birbacher wrote:

Ian Collins schrieb:

No particular reason, just habit. I'm just used to
thinking of a constant pointer to a string literal. A
string literal has to have an address, so where's the extra
pointer?

The pointer itself also has an address. It's one address
more than the array solution has. The array solution saves
sizeof(char*) bytes (or whatever) in the resulting object
file (or it is optimized away).

That was my point, it will more then likely be optimised away.

But the extra pointer reduces the probability that the string
literal itself will be optimized away, since it is actually
"used". (Of course, a good compiler should be able to follow
the link---having suppressed the pointer, the string literal is
no longer used. Usual practice for automatic variables, but I
don't know whether this is frequently done for static variables
or not.

--
James Kanze (GABI Software) email:ja*********@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

[anon]

James Kanze wrote:

On Jun 6, 4:02 pm, anon <[e-mail]:

>tech wrote:

>>Hi, I need to define some strings in a header file, they are
to be const Whats the best to choose from below;

>>const std::string s = "Hello";
const char* s = "Hello";
char* s = "Hello";

>I am doing one of two:
const std::string s1 = "Hello";
const char* const s2 = "Hello";

Why the pointer?

Why not?
PS Sorry for very slow response :(

[anon]

James Kanze wrote:

On Jun 6, 4:02 pm, anon <[e-mail]:

>tech wrote:

>>Hi, I need to define some strings in a header file, they are
to be const Whats the best to choose from below;

>>const std::string s = "Hello";
const char* s = "Hello";
char* s = "Hello";

>I am doing one of two:
const std::string s1 = "Hello";
const char* const s2 = "Hello";

Why the pointer?

I just read your other response.
Some functions/methods are expecting const char* as parameter. I know I
could do s1.c_str(), but I could pass directly const char*
I guess just a matter of preferences ;)