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

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

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 data
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 "v=
oid
> main"). Tell me if I'm wrong:
> A pointer in the stack is the same thing as an automatic variable in the
> stack: it is released when you go out of scope, so no problem. Furthermor=
e:
> if you are concerned about eficiency, you shouldn't use the free store
> unless you need it (for example when using dinamically allocated objects)=
=2E
> 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 "wild
> >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 mandatory=
?
> >
> >Thanks
> >Andre
> >
> >
> >
> >
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