Re: [Caml-list] Interfacing with C: bad practice

["Török Edwin" <edwintorok@gmail.com>]

On 08/16/2011 07:27 PM, Richard W.M. Jones wrote:
> Grrr now _my_ program has a bug.
> 
> ----------------------------------------------------------------------
> #include <stdio.h>
> #include <stdlib.h>
> 
> void f (int a, int b);
> int g (void);
> int *global = NULL;
> 
> int
> main (void)
> {
>   int x = 1;
>   global = &x;
>   f (g (), x);
> 
>   exit (0);
> }
> 
> void
> f (int a, int b)
> {
>   printf ("a = %d, b = %d\n", a, b);
> }
> 
> int
> g (void)
> {
>   if (global) {
>     (*global)++;
>     return *global;
>   }
>   else
>     return 42;
> }
> ----------------------------------------------------------------------
> 
> This program doesn't show undefined behaviour.

Undefined behaviour doesn't mean it must show different results with -O2,
it *might* if the compiler decides to do some optimization.

But isn't this 'f(g(), x)' issue the same as the classic example of undefined behaviour with f(++i, ++i)?

Best regards,
--Edwin