CAN WE TYPE CAST AN INTEGER AS (VOID *)X..(Like can I return a value (void *)x)

[Abhishek]

now suppose I have declared an integer value inside a function as
int x;
now if the return type of the function is of type (void *) then can I
write
return((void *)x) in side the function?
I came across this in a document on multithreading in C..I can post the
exact portion of code which works correctly with such an assignment if
you people want.
Please clarify my doubt.I hope I have conveyed it properly.

[Vladimir S. Oka]

Ico wrote:

Vladimir S. Oka <no****@btopenw orld.com> wrote:

Ico wrote:

Hello AbhishV00ek,

Abhishek <ab************ *@gmail.com> wrote:

Vladimir, I think you misread the details in the OP's question: as far
as I onderstood, he is not returning the address of x, but the *value*
of x, casted to void * :
return((void *)x)

Apart from the cast, this is just as valid as returning x intself.

Ico

Vladimir, you muppet! You are henceforth barred from posting before 9 AM
and/or before having at least three (3) mugs of strong coffee!

The above applies to my previous reply, especially (which I still can't
see, and think will have to do un/re-subscribe to c.l.c dance again)!

Clerk, please strike Vladimir's statements in this case.

I'm kneeling on some corns for a while... :-(

Cheers

Vladimir

--
Hark ye, Clinker, you are a most notorious offender. You stand
convicted of sickness, hunger, wretchedness, and want.
-- Tobias Smollet

[Old Wolf]

Eric Sosman wrote:

The O.P. has run across a function whose return type is
`void*' <ot> because of the requirements of a framework that
is not topical here </ot>. However, in the context of the
actual function it makes more sense to return an `int'. The
code tries to do so by converting the `int' to a `void*';
presumably, the caller retrieves the `void*' and converts it
back to an `int' again. The O.P. asks whether C guarantees
that this will work as desired.

The answer (may I have the envelope, please?) is "No."

That said, the dubious practice will in fact work as desired
on many implementations (I suspect it might fail on AS/400, but
I'm not sure of that). Completely portable approaches exist,
but some programmers are too lazy or too unimaginative to use
them. The O.P. is looking at such a programmer's product.

A portable solution within this framework is to make x static
and return its address. Then convert back to (int *) in the
calling function.

[Eric Sosman]

Old Wolf wrote On 01/30/06 08:28,:

Eric Sosman wrote:

The O.P. has run across a function whose return type is
`void*' <ot> because of the requirements of a framework that
is not topical here </ot>. However, in the context of the
actual function it makes more sense to return an `int'. The
code tries to do so by converting the `int' to a `void*';
presumably, the caller retrieves the `void*' and converts it
back to an `int' again. The O.P. asks whether C guarantees
that this will work as desired.

The answer (may I have the envelope, please?) is "No."

That said, the dubious practice will in fact work as desired
on many implementations (I suspect it might fail on AS/400, but
I'm not sure of that). Completely portable approaches exist,
but some programmers are too lazy or too unimaginative to use
them. The O.P. is looking at such a programmer's product.

A portable solution within this framework is to make x static
and return its address. Then convert back to (int *) in the
calling function.

Yes, <ot> but that's not a good idea in multi-
threaded code, which is what the O.P. is studying.
As it happens, the POSIX multi-threading framework
dictates that the signature of the function must be

void* function(void*)

.... and it's easy to use the argument as a pointer
to a place where the "returned" value -- int, double,
or whatever -- can be deposited. </ot>

Another safe way to disguise a smallish integer
as a pointer is to point at something:

char fake[10];
...
void* function(void* arg) {
int x;
...
return &fake[x]; /* 0 <= x <= 10 */
}
...
/* caller: */
int x = (char*)result_o f_f - fake;

--
Er*********@sun .com