pr22591.c

来自「linux下编程用 编译软件」· C语言 代码 · 共 57 行

/* { dg-do run } */
/* { dg-options "-O2" } */

void abort (); 
 
typedef struct _Node 
{ 
  struct _Node *next, *prev; 
} Node; 
 
void __attribute__ ((noinline)) append (Node * q, Node * p) 
{ 
  p->next = q; 
  p->prev = q; 
  q->next = p; 
  q->prev = p; 
} 
 
inline void 
swap (Node ** a, Node ** b) 
{ 
  Node *tmp = *a; 
  *a = *b; 
  *b = tmp; 
} 
 
/* Miscompilation seems to happen here. If one removes the if condition 
   (which should be true) the program works fine.  */ 
void 
ListSwap (Node * x, Node * y) 
{ 
  Node *tmp; 
  if (x->next) 
    { 
      swap (&x->next, &y->next); 
      swap (&x->prev, &y->prev); 
      x->next->prev = x->prev->next = x; 
      y->next->prev = y->prev->next = y; 
    } 
} 
 
int 
main () 
{ 
  Node A, A1, B, B1; 
 
  append (&A, &A1); 
  append (&B, &B1); 
 
  ListSwap (&A, &B); 
 
  if (&A != A.next->prev) 
    abort (); 

  return 0;
}