RE: [Dev-C++] Correct use of pointers

[Per W. <pw...@ia...>]

No, if the compiler doesn't complain about my clumsiness, I would quickly
change to a better one :-)

/Per W

On Fri, 14 Mar 2003, Hal Kellerman wrote:

> small correction - the first line should read
>   int a,b,c,*p =3D &c;
>
> otherwise your are still initializing p to an unknown value (if the compi=
ler
> lets you get away with it)
>
> Hal Kellerman
> ha...@ha...
>
> -----Original Message-----
> From: dev...@li...
> [mailto:dev...@li...]On Behalf Of Per
> Westermark
> Sent: Friday, March 14, 2003 12:19 PM
> To: jo mateix
> Cc: dev...@li...
> Subject: Re: [Dev-C++] Correct use of pointers
>
>
> The problem in this example is that the pointer is not initialized, i.e.
> it doesn't point to anything. An assignment to *p would then send the dat=
a
> just about anywhere, either corrupting the program, corrupting the OS
> (some OS doesn't protect their own memory), or generate an exception if
> outside of accessible memory for a machine with a memory management unit.
>
> Any normally competent compiler should detect this form of pointer abuse,
> and report the use of an uninitialized variable.
>
> Correct use must be either:
>   int a,b,c,*p =3D c;
>   *p =3D a+b; // Assign to c
> or
>   int a,b,*p;
>   p =3D new int;
>   *p =3D a+b;
>   delete p;
>
> /Per W
>
> On Fri, 14 Mar 2003, jo mateix wrote:
>
> > Hello.
> > I don't see any problem with your example (except for the non-standard
> "void
> > main"). Tell me if I'm wrong:
> > A pointer in the stack is the same thing as an automatic variable in th=
e
> > stack: it is released when you go out of scope, so no problem.
> Furthermore:
> > if you are concerned about eficiency, you shouldn't use the free store
> > unless you need it (for example when using dinamically allocated object=
s).
> > If you all don't aggree, please let me know. Thanks.
> >
> >
> >
> > >From: Andr=E9 Mac=E1rio Barros <and...@su...>
> > >To: "Dev-Cpp-Users" <dev...@li...>
> > >Subject: [Dev-C++] Correct use of pointers
> > >Date: Thu, 13 Mar 2003 21:46:02 -0300
> > >
> > >Gentlemen,
> > >
> > >    Even in the Ritchie=B4s books sometimes I fount .C codes using "wi=
ld
> > >pointers" or something
> > >like:
> > >****************
> > >void main()
> > >{
> > >    int *p, a, b;
> > >
> > >    a=3D2;
> > >    b=3D3;
> > >    *p =3D a + b;
> > >
> > >    ...
> > >}
> > >****************
> > >But... in large programs we can have problems.
> > >
> > >    Would I be corret, allways, if I use insted a code like:
> > >*********************
> > >#include <stdlib.h> /* or alloc.h */
> > >
> > >void main()
> > >{
> > >    int *p, a, b;
> > >
> > >    p=3Dmalloc(1*sizeof(int));
> > >    a=3D2;
> > >    b=3D3;
> > >    *p =3D a + b;
> > >    ...
> > >    free(p);
> > >}
> > >******************
> > >1. It=B4s not necessary, but is it tecnically correct?
> > >2. Is there any point, where the previous memory allocation is mandato=
ry?
> > >
> > >Thanks
> > >Andre
> > >
> > >
> > >
> > >
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