Re: pointer q

On Sun, 14 May 2006 08:48:41 -0400, Eric Sosman
<esosman@xxxxxxxxxxxxxxxxxxx> wrote:
Joe Smith wrote:
"Keith Thompson" <kst-u@xxxxxxx> wrote in message
news:lnlkt5bqv3.fsf@xxxxxxxxxxxxxxxxxx

"Joe Smith" <grumpy196884@xxxxxxxxxxx> writes:

A recent post of mine showed a sufficiently large gaffe on pointers as to
need to return to K&R 5.1-6 appendix A8.6.1 . So we have type
specifiers:
int
long
. One dreams himself variable names: qwe, qwr, writes

int qwe;
long qwr;

and thinks he knows what types he's declared. Had you asked me about:

int *qwe;
long *qwr;

I would have said the pointers declared were--while pointng to different
types--of the same type. Why am I wrong? Joe

int* and long* are two different types (both pointer types).

I'm curious, what led you to think that they're the same type?


What's to stop me from swapping an int * and a long *? Joe

Assume sizeof(int) < sizeof(long), and consider

long l = 42;
int *ip = &l; /* illegal, but Let's Pretend */
*ip = 76;

What value is now stored in `l'?

That's why int* and long* aren't interchangeable.

and so where is the problem?
the problem is different cpus store data in different ways

here

#include <stdio.h>

int main ( void )
{int l = 42;
short *ip = &l; /* illegal, but Let's Pretend */

*ip = 76;
printf(" sizeof(short)==%u sizeof(int)==%u \n",
(unsigned) sizeof(short), (unsigned) sizeof(int));
printf("l==%d\n", l);
return 0;
}

sizeof(short)==2 sizeof(int)==4
l==76

all ok

the problem is "it is easy to obfuscate and make difficult
what it is easy" and it is in the cpu design

another example could be why not exchange "str* and sprintf, etc"
with a secure
int s?prinf(char* strig, int size_of_string, char* fmt, ...);?

because it is easier "to do difficult what is easy" then
Bugtraq is full of error for the C language
.

Relevant Pages

  • pointer q
    ... A recent post of mine showed a sufficiently large gaffe on pointers as to ... One dreams himself variable names: qwe, qwr, writes ... int qwe; ...
    (comp.lang.c)
  • Re: pointer q
    ... One dreams himself variable names: qwe, qwr, writes ... int qwe; ...
    (comp.lang.c)
  • Re: pointer q
    ... qwe, qwr, writes ... int qwe; ... You can do the assignments with explicit conversion, ...
    (comp.lang.c)
  • Re: pointer q
    ... qwe, qwr, writes ... int qwe; ... Joe ...
    (comp.lang.c)
  • Re: pointer q
    ... Joe Smith wrote: ... qwe, qwr, writes ... int qwe; ...
    (comp.lang.c)