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Does anyone know why

void main(){
double x;
double *y;
(int) y = x;
}

compiles well, and why

void main(){
double x;
double *y;
(double) y = x;
}

does not compile well ?!?
Why is it not allowed to cast a pointer to a double in the seconde case ?
Thanks
Yacine

Yacine <> wrote:

> Does anyone know why
>
> void main(){
> double x;
> double *y;
> (int) y = x;
> }
>
> compiles well,

Because your implementation is broken, or you're calling it the wrong
way. main() returns int. The cast and subsequent assignment are about as
dubious as Bush Junior's veracity, btw.

> void main(){
> double x;
> double *y;
> (double) y = x;
> }
>
> does not compile well ?!?

Because casting a pointer to int is dubious, but possible, while casting
a pointer to double makes no sense at all.

Richard

Yacine <> spoke thus:

> void main(){

Hold it right there. Sounds like you could use

http://www.eskimo.com/~scs/C-faq/top.html

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cyberspace.org | don't, I need to know. Flames welcome.

Richard Bos wrote:
> Yacine <> wrote:
>
>
>>Does anyone know why
>>
>>void main(){
>> double x;
>> double *y;
>> (int) y = x;
>>}
>>
>>compiles well,
>
>
> Because your implementation is broken, or you're calling it the wrong
> way. main() returns int. The cast and subsequent assignment are about as
> dubious as Bush Junior's veracity, btw.
>
>
>>void main(){
>> double x;
>> double *y;
>> (double) y = x;
>>}
>>
>>does not compile well ?!?
>
>
> Because casting a pointer to int is dubious, but possible, while casting
> a pointer to double makes no sense at all.
>
> Richard
The return type of main has nothing to do with the problem I'm talking
about. My question is: is it possible to cast a pointer to a double ? I
think it does not make more sense to cast a pointer to int than casting
a pointer to double ...

Yacine wrote:
>
> Does anyone know why
>
> void main(){
> double x;
> double *y;
> (int) y = x;
> }
>
> compiles well,

Because you are not using a conforming implementation of C.
A cast on the left operand of the assignment operator
is a constraint violation.

--
pete

pete wrote:

> Yacine wrote:
>
>>Does anyone know why
>>
>>void main(){
>> double x;
>> double *y;
>> (int) y = x;
>>}
>>
>>compiles well,
>
>
> Because you are not using a conforming implementation of C.
> A cast on the left operand of the assignment operator
> is a constraint violation.
>
How can I handle that problem ?

Yacine wrote:
>
> pete wrote:
>
> > Yacine wrote:
> >
> >>Does anyone know why
> >>
> >>void main(){
> >> double x;
> >> double *y;
> >> (int) y = x;
> >>}
> >>
> >>compiles well,
> >
> >
> > Because you are not using a conforming implementation of C.
> > A cast on the left operand of the assignment operator
> > is a constraint violation.
> >
> How can I handle that problem ?

If you have made sure that there are no alignment problems
and no size problems, then you can

*(int *)&y = x;

If you haven't made sure, then don't do that.

--
pete

Yacine wrote:

> Does anyone know why
>
> void main()

int main(void)

{
> double x;
> double *y;
> (int) y = x;
> }
>
> compiles well,

You can't assign to a value, only to an object. (int)y is a value, not an
object. You should get a diagnostic. Turn up your warning level.

> and why
>
> void main()

int main(void)

{
> double x;
> double *y;
> (double) y = x;
> }
>
> does not compile well ?!?

Same reason the first one shouldn't. You can't assign to a value, only to an
object. (double)y is a value, not an object.

--
Richard Heathfield :
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

pete wrote:
>
> Yacine wrote:
> >
> > pete wrote:
> >
> > > Yacine wrote:
> > >
> > >>Does anyone know why
> > >>
> > >>void main(){
> > >> double x;
> > >> double *y;
> > >> (int) y = x;
> > >>}
> > >>
> > >>compiles well,
> > >
> > >
> > > Because you are not using a conforming implementation of C.
> > > A cast on the left operand of the assignment operator
> > > is a constraint violation.
> > >
> > How can I handle that problem ?
>
> If you have made sure that there are no alignment problems
> and no size problems, then you can
>
> *(int *)&y = x;

*(int *)&y = (int)x;

Excuse me, I forgot how invloved it was.

> If you haven't made sure, then don't do that.

--
pete

pete wrote:
>
> pete wrote:
> >
> > Yacine wrote:
> > >
> > > pete wrote:
> > >
> > > > Yacine wrote:
> > > >
> > > >>Does anyone know why
> > > >>
> > > >>void main(){
> > > >> double x;
> > > >> double *y;
> > > >> (int) y = x;
> > > >>}
> > > >>
> > > >>compiles well,
> > > >
> > > >
> > > > Because you are not using a conforming implementation of C.
> > > > A cast on the left operand of the assignment operator
> > > > is a constraint violation.
> > > >
> > > How can I handle that problem ?
> >
> > If you have made sure that there are no alignment problems
> > and no size problems, then you can
> >
> > *(int *)&y = x;
>
> *(int *)&y = (int)x;
>
> Excuse me, I forgot how invloved it was.

You also have to make sure that (int)x is an integer value.

--
pete