#include <stdio.h>

#define dynamic_struct_name(type, name)        \
  __dynamic_ ## type ## _ ## name ## _struct__ \

#define dynamic_cleanup_name(type, name)        \
  __dynamic_ ## type ## _ ## name ## _cleanup__ \

#define dynamic_save_name(name) \
  __dynamic_ ## name ## _save__ \

#define dynamic_continue_name(name) \
  __dynamic_ ## name ## _continue__ \

#define dynamic_struct_def(type, name)  \
  typedef struct {                      \
    type * target;                      \
    type data;                          \
  } dynamic_struct_name(type, name)     \

#define dynamic_cleanup_def(type, name)       \
  void dynamic_cleanup_name(type, name)       \
    (dynamic_struct_name(type, name) * arg) { \
    *(*arg).target = (*arg).data;             \
  }                                           \

#define dynamic_var(type, name, value) \
  dynamic_struct_def(type, name);      \
  dynamic_cleanup_def(type, name);     \
  type name = value                    \

#define dynamic_bind_aux(type, name, value, stype, save, pop, var)      \
  for(int var = 1; var;)                                                \
    for(stype save __attribute__((cleanup(pop))) = {&name, name}; var;) \
      for(name = value; var; var = 0)                                   \

#define dynamic_bind(type, name, value)              \
  dynamic_bind_aux(type, name, value,                \
                   dynamic_struct_name(type, name),  \
                   dynamic_save_name(name),          \
                   dynamic_cleanup_name(type, name), \
                   dynamic_continue_name(name))      \

dynamic_var(int, x, 5);

int bar() {
  printf("We are in bar, x = %d\n", x);
  return x;
}

int foo() {
  dynamic_bind(int, x, 42) {
    printf("bar(): %d\n", bar());
    x = 222;
    return bar();
  }
}

int main(int argc, char** argv) {
  printf("bar(): %d\n", bar());
  printf("foo(): %d\n", foo());
  printf("bar(): %d\n", bar());
  return 0;
}