c90-array-lval-2.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

/* Test for non-lvalue arrays decaying to pointers: in C99 only.  */
/* Origin: Joseph Myers <[e-mail]> */
/* { dg-do compile } */
/* { dg-options "-std=iso9899:1990 -pedantic-errors" } */

struct s { char c[17]; };

struct s x;

extern struct s foo (void);

#define ASSERT(v, a)	char v[((a) ? 1 : -1)]

ASSERT (p, sizeof (x.c) == 17);
ASSERT (q, sizeof (0, x.c) == sizeof (char *));
ASSERT (r, sizeof ((foo ()).c) == 17);
/* The non-lvalue array does not decay to a pointer, so the comma expression
   has (non-lvalue) array type.
*/
ASSERT (s, sizeof (0, (foo ()).c) == 17); /* { dg-bogus "array" "bad non-lvalue array handling" } */