------- Additional Comments From rpedersen at atmel dot com 2005-06-13 11:56 ------- (In reply to comment #5) > (In reply to comment #0) > > I think that the C standard says C that the "name" of variable > > becomes an rvalue (the actual value) thus requires that the variable > > is accessed. > > It actually says that accessing a volatile qualified object through a nonvolatile > qualified lvalue (as would be the case if referenced via a non-volatile qualified > cast expression) is implementation defined. >
If you are correct, the proposed testcase might be misleading. Changing the expression for accessing the volatile member of the struct to: "(volatile int)ptr->b;" or just: "ptr->b;" still leads to the access being optimized away. > Personally, it seems more consistent to abide by the semantics specified > by a programmer's explicit cast expression, thereby if given: > > int x, y; > const int *z; > > x = (volatile int)y; // specifies a reference to a volatile int object. > > z = &(const int)x; // specifies a reference to a const int object. > > And correspondingly: > > int x; > volatile int y; > const int z; > > x = (int)y; // cast's away volatile (therefore may be optimized away), > // therefore if not desired, shouldn't be "cast away". > > (int)z = x; // cast's away const (although may generate a run-time > // exception if referencing a READONLY allocated object), > // therefore if not desired, shouldn't be "cast away". > I agree with you on this. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22000
