[Bug c++/13397] New: Optimizer doesn't take into account protection flags

["yuri at tsoft dot com" <gcc-bugzilla at gcc dot gnu dot org>]

The following piece of code could have been optimized better
if optimizer had taken into account that certain
field is "private".

If some field is private in the class and all function
members are explicitely defined in the class it's no
way private field legitimately changes in other than
by these methods way (assuming no friend classes).

Example:
----cut---------------------------------------------------
#include <stdio.h>

class C {
  public: C() : c('a'), pc(&c)  { }
  private: char *pc;
  public: char *get_pc() { return (pc); }
  private: char c;
};

extern void f(C *);

int main(int argc, const char *argv) {
  C c;
  f(&c);
  if (c.get_pc() != NULL) {
    printf("YES\n");
  } else {
    printf("NO\n");
  }
}
----------cut(end code)--------------------------

In the above code it's clear that field pc is never
not NULL so it's no need to compare the
value returned by get_pc() function. And
"NO" should never appear in the assembly.

But it appears though.

Same would also apply for any other type
if class methods only change the value
in particular way and no it's pointers
leaked and no friend classes declared.

Yuri.

-- 
           Summary: Optimizer doesn't take into account protection flags
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: yuri at tsoft dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: Any Linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13397