why does this pointer work?

[jagguy]

this works

char *p ;

p="xat";

cout << p <<endl;

i thought you need something like this

char *p=new char[10];

[Jim Langston]

"jagguy" <jo**********@o ptusnet.com.au> wrote in message
news:44******** **************@ news.optusnet.c om.au...

this works

char *p ;

p="xat";
"xat" is a constant char array and p now points to it.
cout << p <<endl;

i thought you need something like this

char *p=new char[10];

[Eric Jensen]

"jagguy" <jo**********@o ptusnet.com.au> wrote in message
news:44******** **************@ news.optusnet.c om.au...

this works

char *p ;

p="xat";

cout << p <<endl;

i thought you need something like this

char *p=new char[10];

Sure it works. It equilant to this code

const char *str = "xat";
char *p = (char *)str;
cout << p << endl;

When the compiler generates the assembly
"xat" goes into the data segment as a const.with some address
when you do p = "xat" the compiler just set the address pointed by p to the
address of "xat" in the data segment.

//eric

[jagguy]

char *p ;

p="xbbat";

cout << p <<endl;


i thought you need something like this

char *p=new char[10];

Sure it works. It equilant to this code

const char *str = "xat";
char *p = (char *)str;
cout << p << endl;

When the compiler generates the assembly
"xat" goes into the data segment as a const.with some address
when you do p = "xat" the compiler just set the address pointed by p to
the address of "xat" in the data segment.

//eric

if it is a constant then this shouldn't work but it odes

char *p ;

p="xbbat";

cout << p <<endl;

p="xbbat";

cout << p <<endl;

[jagguy]

"Eric Jensen" <er**@no.spam.c om> wrote in message
news:44******** *************** @dread16.news.t ele.dk...

"jagguy" <jo**********@o ptusnet.com.au> wrote in message
news:44******** **************@ news.optusnet.c om.au...

this works

char *p ;

p="xat";

cout << p <<endl;

i thought you need something like this

char *p=new char[10];

Sure it works. It equilant to this code

const char *str = "xat";
char *p = (char *)str;
cout << p << endl;

When the compiler generates the assembly
"xat" goes into the data segment as a const.with some address
when you do p = "xat" the compiler just set the address pointed by p to
the address of "xat" in the data segment.

//eric

if it is a constant then this shouldn't work but it odes

char *p ;

p="xbbat";

cout << p <<endl;

p="xbbat";

cout << p <<endl;

[Eric Jensen]

"jagguy" <jo**********@o ptusnet.com.au> wrote in message
news:44******** *************** @news.optusnet. com.au...

if it is a constant then this shouldn't work but it odes

char *p ;

p="xbbat";

cout << p <<endl;

p="xbbat";

cout << p <<endl;

char *p; // <- this is just a pointer. it points to a location in memory

"xbbat" is a string literal, located inside the binary (.exe).
When you run your program it's loaded into memory.
you assignments will only set the value of the pointer p to point at the
area in memory that contains the string "xbbat" (wich is loaded into memory
with the program when executed).

char *p;
p = "string";

You do not assign the value "string" to p.
You do only set the value of p to the address in memory where the first char
of "string" is located.

However, you should not do what your doing.

It would make more sense to write:
const char *p = "sometext";
std::cout << p << std::endl;

witch is basicly the same as what you do.

//eric

[benben]

jagguy wrote:

this works

char *p ;

p="xat";

cout << p <<endl;

i thought you need something like this

char *p=new char[10];

An analogue to your code is:

int a = 100;
int p = &a;

cout << *p;

The pointer points to a valid memory, it should work.

Ben

[Tomás]

int a = 100;
int p = &a;

cout << *p;

int *p = &a;
(Although I presume it was nothing more than a typo)
-Tomás

[Tomás]

jagguy posted:

this works

char *p ;

p="xat";

cout << p <<endl;

i thought you need something like this

char *p=new char[10];

You posted two separate threads, and now the replies are all over the
place.

I left you a reply in the other thread.
-Tomás

[Bo Persson]

"jagguy" <jo**********@o ptusnet.com.au> skrev i meddelandet
news:44******** *************** @news.optusnet. com.au...

if it is a constant then this shouldn't work but it odes

char *p ;

p="xbbat";

cout << p <<endl;

p="xbbat";

cout << p <<endl;

It is a special rule for string literals. You can assign their address
(a const pointer) to a non-const char pointer.

Originally, the C language didn't have const, so

char* p = "Hello";

has always worked this way.

Later when C++ made string literals constants, this special rule was
added to support old C code. It doesn't work for any other kind of
pointers.
Bo Persson