size_t

[studentc]

newbie question -- really basic question
What is size_t

[Dave_Sinkula]

size_t "is the unsigned integer type of the result of the sizeof operator"

[Thantos]

In the simplist terms an unsigned long integer

Drat beaten, thats what I get for looking at my includes directory

[linuxdude]

^^usually. It is there for portability. but in simple terms they are both right

[ShortCoder]

It is there because (I assume) it is different sizes on different platforms but if you're just using size_t rather than int or long or short or whatever then it won't really matter how it was chosen to be implemented there.

[studentc]

can i then replace my int with size_t

is
size_t "is the unsigned integer type of the result of the sizeof operator"

the same as

size_t "is the unsigned integer value of the result of the sizeof operator"

[linuxdude]

say a function returned a sizeof command ex

int size_of(char *string){
     return (sizeof(string));
}

It would be more portable to do this

size_t size_of(char *string){
     return (sizeof(string));
}

It doesn't have to be a function it could be a variable like the one that would recieve the return of the latter function
[edit] man at functions like malloc or qsort. say you want to malloc a variable amount

int var;
int *ptr;
get var from user 
ptr=malloc(var*sizeof(int));

or

size_t var;
int *ptr;
get var from user 
ptr=malloc(var*sizeof(int));

See the difference. And of course error checking has been left out for example's sake.

[quzah]

Bad example. Your function will return the size of the pointer. You can't use sizeof on a pointer and expect it to give you the size of the string, unless the pointer is the name of an array created in that same scope. This was just beatend to death recently in another thread.

Quzah.

[linuxdude]

whoops wasn't really paying attention. I just read that thread too. Sorry, I hope he gets my point though with the malloc example.

[pinko_liberal]

can i then replace my int with size_t

is
size_t "is the unsigned integer type of the result of the sizeof operator"

the same as

size_t "is the unsigned integer value of the result of the sizeof operator"

First all you can safely assume for all compilers is that size_t is an unsigned integer type (it might be unsigned int, unsigned long, ....). If you have a c99 compiler, the constant SIZE_MAX defined in stdint.h should give you the maximum possible value that size_t variable can have. For a proper C99 compiler SIZE_MAX should be at least 65535

Secondly, no you cannot replace int with size_t in general because int can take both negative and positive values whereas size_t cannot.

[Emmanuel Delaha]

In the simplist terms an unsigned long integer

size_t is defined as an unsigned integer. Not necessarely 'long'. Actually, on my ol'good Borland C, it's an unsigned int.

[Emmanuel Delaha]

can i then replace my int with size_t

is
size_t "is the unsigned integer type of the result of the sizeof operator"

the same as

size_t "is the unsigned integer value of the result of the sizeof operator"

Of course no. A type is certainely not a value.

To answer your first question, size_t is useful to define a variable holding a size, an length, a number of elements in an array or an index.

I personnally use it massively in these occasions.

[Emmanuel Delaha]

whi it would be more portable to do this
Code:
size_t size_of(char *string){
return (sizeof(string));
}
instead of returning an int or a long? i am still not convinced to why i should use it. someone to convince me?
thnaks

Because the size of an object could be too big for an int.

For example, on my platform (Borland C++ 3.1), the maximum value for an int is

<limits.h>

#define INT_MAX             0x7FFF

and size_t is defined as

<stddef.h>

typedef unsigned size_t;

Obviously, on this platform, an unsigned int can be bigger than an int.

The use of size_t is considered good practice when portability is important.

[Thantos]

1) Welcome to the boards Emmanuel Delaha
2) There is no need to reiterate what others have already said
3) Learn to use edit.
4) The words "Borland" and "good" do not belong in the same sentance

[Emmanuel Delaha]

2) There is no need to reiterate what others have already said

Can you be more specific ? Please give an example of 'reiteration' of mine.

3) Learn to use edit.

Can you be more specific ? Please give an example where I should have used it better.

4) The words "Borland" and "good" do not belong in the same sentance

Unless you have more solid words to build your opinion, I stick to mine that is different.