#include <stdio.h>
#include <string.h>

struct save_rec {
  void *p;                    /* where */
  void *v;                    /* saved value */
  size_t sz;                  /* size of value */
};

static void restore (struct save_rec *s)
{
  memcpy (s->p, s->v, s->sz);
}

#define dynbind(lvalue,val)                                             \
  for (struct {                                                         \
        int k;                                                          \
        __typeof__(lvalue) old;                                         \
       } rec##__LINE__ = { 0, (lvalue) };                               \
       rec##__LINE__.k < 1;)                                            \
    for (struct save_rec save##__LINE__                                 \
         __attribute__ ((cleanup (restore)))                            \
         = { &(lvalue), &rec##__LINE__.old, sizeof (lvalue) };          \
         rec##__LINE__.k < 1;)                                          \
      for ((lvalue) = (val);rec##__LINE__.k < 1;rec##__LINE__.k++)

/* Demo */

int xyz = 0;
struct point { int x, y; } pt;

extern int bar (void);

int foo (void)
{
  dynbind (xyz, 42)
    {
      return bar ();
    }
}

int foo_pt (void)
{
  struct point q = { 100, 200 };
  
  dynbind (pt, q)
    {
      return bar ();
    }
}