array perversion

[matevzb]

Since array subscripting is commutative in C, is the following
perversity legal and/or portable? (I don't really intend to use it
anywhere, it just puzzles my mind.)
#include <stdio.h>

int
fcn (void)
{
return 3;
}

int
main (void)
{
int array[] = { 1, 2, 3, 4, 5, 6, 7, 9 };

printf ("%d\n", fcn()[array]);
return 0;
}

It looks a bit confusing though, since the usage resembles the
following:
#include <stdio.h>

int *
fcn2 (void)
{
static int array2[] = { 5, 4, 3, 2, 1, 0 };
return array2;
}

int
main (void)
{
printf ("%d\n", fcn2()[3]);
return 0;
}

 

[Richard Heathfield]

matevzb said:

Since array subscripting is commutative in C, is the following
perversity legal and/or portable? (I don't really intend to use it
anywhere, it just puzzles my mind.)
#include <stdio.h>

int
fcn (void)
{
return 3;
}

int
main (void)
{
int array[] = { 1, 2, 3, 4, 5, 6, 7, 9 };

printf ("%d\n", fcn()[array]);

fcn() is basically 3, so you have 3[array], which is equivalent to array[3],
so yes, this is legal.

return 0;
}

It looks a bit confusing though, since the usage resembles the
following:
#include <stdio.h>

int *
fcn2 (void)
{
static int array2[] = { 5, 4, 3, 2, 1, 0 };
return array2;
}

int
main (void)
{
printf ("%d\n", fcn2()[3]);

Here, fcn2() is basically array2, so you've got *(array2 + 3), which is the
int value 2. Yes, that's legal too.


And either of them will get your legs chopped off if you produce them at the
Fagan inspection.