elide1.c

来自「this is a gcc file, you can download it 」· C语言 代码 · 共 39 行

// { dg-do run }

// Test that the destructor for a temporary passed by value isn't run
// until end of full-expression, as per [class.copy]:

// Whenever a temporary class object is copied using a copy  constructor,
// and  this  object  and  the copy have the same cv-unqualified type, an
// implementation is permitted to treat the original and the copy as  two
// different  ways of referring to the same object and not perform a copy
// at all, even if the class copy constructor  or  destructor  have  side
// effects....                                       In these cases,  the
// object  is  destroyed  at the later of times when the original and the
// copy would have been destroyed without the optimization.

// Here, the temporary would be destroyed later than the parm, so either we
// must suppress the optimization in this case or destroy value parms in the
// caller.

int d;

struct A {
  A () { }
  A (const A&) { }
  ~A() { ++d; }
};

void f (A a) { }

int main ()
{
  int r;
  f (A ()), r = d;

  if (r < d && d)
    return 0;
  else
    return 1;
}